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Sample records for attosecond electron-hole dynamics

  1. Attosecond electron dynamics in molecules and liquids

    Science.gov (United States)

    WöRner, Hans Jakob

    The ultrafast motion of electrons and holes following light-matter interaction is fundamental to a broad range of chemical and biophysical processes. In this lecture, I will discuss some of our recent experiments that measure the atomic-scale motion of charge with attosecond temporal resolution (1 as = 10-18s). The first experiment is carried out on isolated, spatially oriented molecules in the gas phase. Using high-harmonic spectroscopy, we resolve the migration of an electron hole across the molecule with a resolution of 100 as and simultaneously demonstrate extensive control over charge migration. In the second class of experiments, we use an attosecond pulse train synchronized with a near-infrared laser pulse to temporally resolve the process of photoemission from molecules in the gas phase and from a liquid-water microjet, resolving electron transport through liquid water on the attosecond time scale.

  2. Vlasov simulations of electron hole dynamics in inhomogeneous magnetic field

    Science.gov (United States)

    Kuzichev, Ilya; Vasko, Ivan; Agapitov, Oleksiy; Mozer, Forrest; Artemyev, Anton

    2017-04-01

    Electron holes (EHs) or phase space vortices are solitary electrostatic waves existing due to electrons trapped within EH electrostatic potential. Since the first direct observation [1], EHs have been widely observed in the Earth's magnetosphere: in reconnecting current sheets [2], injection fronts [3], auroral region [4], and many other space plasma systems. EHs have typical spatial scales up to tens of Debye lengths, electric field amplitudes up to hundreds of mV/m and propagate along magnetic field lines with velocities of about electron thermal velocity [5]. The role of EHs in energy dissipation and supporting of large-scale potential drops is under active investigation. The accurate interpretation of spacecraft observations requires understanding of EH evolution in inhomogeneous plasma. The critical role of plasma density gradients in EH evolution was demonstrated in [6] using PIC simulations. Interestingly, up to date no studies have addressed a role of magnetic field gradients in EH evolution. In this report, we use 1.5D gyrokinetic Vlasov code to demonstrate the critical role of magnetic field gradients in EH dynamics. We show that EHs propagating into stronger (weaker) magnetic field are decelerated (accelerated) with deceleration (acceleration) rate dependent on the magnetic field gradient. Remarkably, the reflection points of decelerating EHs are independent of the average magnetic field gradient in the system and depend only on the EH parameters. EHs are decelerated (accelerated) faster than would follow from the "quasi-particle" concept assuming that EH is decelerated (accelerated) entirely due to the mirror force acting on electrons trapped within EH. We demonstrate that EH propagation in inhomogeneous magnetic fields results in development of a net potential drop along an EH, which depends on the magnetic field gradient. The revealed features will be helpful for interpreting spacecraft observations and results of advanced particle simulations. In

  3. Ultrafast carrier dynamics in tetrahedral amorphous carbon: carrier trapping versus electron-hole recombination

    International Nuclear Information System (INIS)

    Carpene, E; Mancini, E; Dallera, C; Schwen, D; Ronning, C; Silvestri, S De

    2007-01-01

    We report the investigation of the ultrafast carrier dynamics in thin tetrahedral amorphous carbon films by means of femtosecond time-resolved reflectivity. We estimated the electron-phonon relaxation time of a few hundred femtoseconds and we observed that under low optical excitation photo-generated carriers decay according to two distinct mechanisms attributed to trapping by defect states and direct electron-hole recombination. With high excitation, when photo-carrier and trap densities are comparable, a unique temporal evolution develops, as the time dependence of the trapping process becomes degenerate with the electron-hole recombination. This experimental evidence highlights the role of defects in the ultrafast electronic dynamics and is not specific to this particular form of carbon, but has general validity for amorphous and disordered semiconductors

  4. Dynamical effects of electron-hole correlation and giant quantum attenuation of ultrasound in semimetals

    International Nuclear Information System (INIS)

    Kuramoto, Y.

    1982-01-01

    The giant quantum attenuation of ultrasound in bismuth and other semimetals is noticeably enhanced when certain pair of Landau subbands of electrons and holes participate simultaneously in an attenuation peak. A theoretical analysis is presented which emphasizes importance of dynamical effects of the electron-hole correlation. In the temperature range between 1K and 4K covered by most experiments, the correlation effect is found to be weak on the real part of the relevant response function which gives change in sound velocity. This implies that equilibrium properties of the system are not much influenced by the correlation effect. Nonetheless, the electron-hole correlation is shown to have a drastic consequence on the imaginary part of the response function probed by the ultrasonic attenuation. Proposal for experiment is advanced to discriminate relative importance of this exciton-like correlation from that of repulsive correlation between carriers with the same charge. (orig.)

  5. Attosecond dynamics of electrons in molecules and liquids

    Science.gov (United States)

    Woerner, Hans Jakob

    2016-05-01

    The ultrafast motion of electrons and holes following light-matter interaction is fundamental to a broad range of chemical and biophysical processes. In this lecture, I will discuss two recent experiments carried out in our group that measure the atomic-scale motion of charge with attosecond temporal resolution (1 as = 10-18 s). The first experiment is carried out on isolated, spatially oriented molecules in the gas phase. We advance high-harmonic spectroscopy to resolve spatially and temporally the migration of an electron hole immediately following ionization of iodoacetylene, while simultaneously demonstrating extensive control over the process. A multidimensional approach, based on the measurement of both even and odd harmonic orders, enables us to reconstruct both quantum amplitudes and phases of the electronic states with a resolution of ~ 100 as. We separately reconstruct quasi-field-free and laser-controlled charge migration as a function of the spatial orientation of the molecule and determine the shape of the hole created by ionization. The second experiment is carried out on a free-flowing microjet of liquid water. We use an attosecond pulse train synchronized with a near-infrared laser pulse to temporally resolve the process of photoemission from liquid water using the RABBIT technique. We measure a delay on the order of 50 as between electrons emitted from the HOMO of liquid water compared to that of gas-phase water and a substantially reduced modulation contrast of the corresponding sidebands. Since our measurements on solvated water molecules are referenced to isolated ones, the measured delays reflect (i) the photoionization delays caused by electron transport through the aqueous environment and (ii) the effect of solvation on the parent molecule. The relative modulation contrast, in turn, contains information on (iii) the modification of transition amplitudes and (iv) dephasing processes. These experiments make the liquid phase and its fascinating

  6. Isolated sub-100-attosecond pulse generation via controlling electron dynamics

    OpenAIRE

    Lan, Pengfei; Lu, Peixiang; Cao, Wei; Li, Yuhua; Wang, Xinlin

    2007-01-01

    A new method to coherently control the electron dynamics is proposed using a few-cycle laser pulse in combination with a controlling field. It is shown that this method not only broadens the attosecond pulse bandwidth, but also reduces the chirp, then an isolated 80-as pulse is straightforwardly obtained and even shorter pulse is achievable by increasing the intensity of the controlling field. Such ultrashort pulses allow one to investigate ultrafast electronic processes which have never be a...

  7. How can attosecond pulse train interferometry interrogate electron dynamics?

    Science.gov (United States)

    Arnold, C. L.; Isinger, M.; Busto, D.; Guénot, D.; Nandi, S.; Zhong, S.; Dahlström, J. M.; Gisselbrecht, M.; l'Huillier, A.

    2018-04-01

    Light pulses of sub-100 as (1 as=10-18 s) duration, with photon energies in the extreme-ultraviolet (XUV) spectral domain, represent the shortest event in time ever made and controlled by human beings. Their first experimental observation in 2001 has opened the door to investigating the fundamental dynamics of the quantum world on the natural time scale for electrons in atoms, molecules and solids and marks the beginning of the scientific field now called attosecond science.

  8. Correlated proton-electron hole dynamics in protonated water clusters upon extreme ultraviolet photoionization

    Directory of Open Access Journals (Sweden)

    Zheng Li

    2016-07-01

    Full Text Available The ultrafast nuclear and electronic dynamics of protonated water clusters H+(H2On after extreme ultraviolet photoionization is investigated. In particular, we focus on cluster cations with n = 3, 6, and 21. Upon ionization, two positive charges are present in the cluster related to the excess proton and the missing electron, respectively. A correlation is found between the cluster's geometrical conformation and initial electronic energy with the size of the final fragments produced. For situations in which the electron hole and proton are initially spatially close, the two entities become correlated and separate in a time-scale of 20 to 40 fs driven by strong non-adiabatic effects.

  9. Correlated proton-electron hole dynamics in protonated water clusters upon extreme ultraviolet photoionization

    Science.gov (United States)

    Li, Zheng; Vendrell, Oriol

    2016-01-01

    The ultrafast nuclear and electronic dynamics of protonated water clusters H+(H2O)n after extreme ultraviolet photoionization is investigated. In particular, we focus on cluster cations with n = 3, 6, and 21. Upon ionization, two positive charges are present in the cluster related to the excess proton and the missing electron, respectively. A correlation is found between the cluster's geometrical conformation and initial electronic energy with the size of the final fragments produced. For situations in which the electron hole and proton are initially spatially close, the two entities become correlated and separate in a time-scale of 20 to 40 fs driven by strong non-adiabatic effects. PMID:26798842

  10. Attosecond science

    Science.gov (United States)

    Villeneuve, D. M.

    2018-01-01

    Scientists have been developing sources of light with ever-shorter pulse durations, in order to study motion in systems ranging from a golfer's swing to the motion of atoms within molecules. The shortest pulses produced to date are under 60 attoseconds, i.e. ? s. One attosecond is to one second as one second is to the age of the universe. For comparison, the classical orbital period of an electron in a hydrogen atom is 150 attoseconds. Attosecond pulses were first produced in 2001. This article describes how attosecond pulses are generated and how they are measured. Some applications of attosecond pulses are described, such as measuring the delay in photoionisation, or observing molecular dissociation dynamics.

  11. Attosecond Electron Wave Packet Dynamics in Strong Laser Fields

    International Nuclear Information System (INIS)

    Johnsson, P.; Remetter, T.; Varju, K.; L'Huillier, A.; Lopez-Martens, R.; Valentin, C.; Balcou, Ph.; Kazamias, S.; Mauritsson, J.; Gaarde, M. B.; Schafer, K. J.; Mairesse, Y.; Wabnitz, H.; Salieres, P.

    2005-01-01

    We use a train of sub-200 attosecond extreme ultraviolet (XUV) pulses with energies just above the ionization threshold in argon to create a train of temporally localized electron wave packets. We study the energy transfer from a strong infrared (IR) laser field to the ionized electrons as a function of the delay between the XUV and IR fields. When the wave packets are born at the zero crossings of the IR field, a significant amount of energy (∼20 eV) is transferred from the field to the electrons. This results in dramatically enhanced above-threshold ionization in conditions where the IR field alone does not induce any significant ionization. Because both the energy and duration of the wave packets can be varied independently of the IR laser, they are valuable tools for studying and controlling strong-field processes

  12. Attosecond Charge Migration with TDDFT: Accurate Dynamics from a Well-Defined Initial State.

    Science.gov (United States)

    Bruner, Adam; Hernandez, Samuel; Mauger, François; Abanador, Paul M; LaMaster, Daniel J; Gaarde, Mette B; Schafer, Kenneth J; Lopata, Kenneth

    2017-09-07

    We investigate the ability of time-dependent density functional theory (TDDFT) to capture attosecond valence electron dynamics resulting from sudden X-ray ionization of a core electron. In this special case the initial state can be constructed unambiguously, allowing for a simple test of the accuracy of the dynamics. The response following nitrogen K-edge ionization in nitrosobenzene shows excellent agreement with fourth-order algebraic diagrammatic construction (ADC(4)) results, suggesting that a properly chosen initial state allows TDDFT to adequately capture attosecond charge migration. Visualizing hole motion using an electron localization picture (ELF), we provide an intuitive chemical interpretation of the charge migration as a superposition of Lewis dot resonance structures.

  13. Investigation of attosecond ionization dynamics in gases and solids with intense few-cycle laser pulses

    International Nuclear Information System (INIS)

    Mitrofanov, A. V.

    2011-01-01

    Interaction of intense light fields with dielectric materials has fascinated scientists since the invention of pulsed lasers in the early sixties. Despite the many decades of research, the interest in the field keeps growing because of the potential technological applications of optical (meta-) materials and the prospects of light-controlled peta-Hertz electronics as well as the improving understanding of the fundamental processes behind light-matter interactions. The progress in the short-pulse laser technology that delivered ever-shorter light pulses was echoed by the discoveries of different progressively shorter time scales in the cycle of excitation and energy/charge relaxation in transparent solids, many parts of which are now well understood. The ultimate challenge lies in recovering the earliest stages of the dynamics which are linked to optical-field-ionization that proceeds within a fraction of an optical cycle. One of the complications of advancing the attosecond science to the bulk media is the problem of inducing and detecting a synchronized attosecond response. The charged particles spectroscopy, well developed in gaseous media during last decade and capable of reaching an attosecond temporal resolution cannot be used as an experimental tool for investigation since direct detection of charged particles is impossible in the volume of a solid material. However, solids are the natural place where electronic processes on the sub-femtosecond or attosecond time scale are expected. Very recently several methods for measuring attosecond dynamics in condensed media have been proposed utilizing optical fields in the transparency range of the material. In this thesis a method, suggested in our scientific group is presented. It is an all-optical method based on the detection of optical harmonics originating from ultrafast modulation of a free electron current due to ionization in the field of intense few-cycle laser pulses. This technique will allow retrieving

  14. Control and dynamics of attosecond electron wave packets in strong laser fields

    International Nuclear Information System (INIS)

    Johnsson, P.; Remetter, T.; Varju, K.; L'Huillier; Lopez-Martens, R.; Valentin, C.; Balcou, P.; Kazamias, S.; Mauritsson, J.; Gaarde, M.B.; Schafer, K.J.; Mairess, Y.; Wabnitz, H.; Boutu, W.; Salieres, P.

    2005-01-01

    Full text: Trains of attosecond pulses, emerging from the phase-locking of high-order harmonics generated in a strong laser field are now being routinely produced and characterized in a few laser laboratories. Attosecond pulse trains (APTs) are flexible attosecond sources, since the amplitude and relative phase of the spectral components (the harmonics) can be tailored, allowing us to vary both the duration and the carrier frequency of the pulses. Attosecond pulses interacting with a gas of atoms generate electron wave packets (EWPs), which are temporally localized with approximately the same duration as the attosecond pulses. In contrast to the tunneling electron wave packets giving rise to processes such as high-order harmonic generation and above-threshold-ionization (ATI), the properties of these EWPs are inherited from the attosecond pulses through the single-photon ionization step. Thus the energy and temporal characteristics of the EWPs can be varied independently of the process under investigation, by controlling the properties of the attosecond pulses. This talk will describe two recent experiments done in Lund. First we report on the generation, compression and delivery on target of ultrashort extreme-ultraviolet light pulses using external amplitude and phase control. The APT is synthesized from the 13 th to 35 th harmonics of a 35 fs Ti:sapphire laser. The harmonics are generated by focusing the laser beam into a window-less gas cell, filled with argon. To achieve the required on-target attosecond pulses, the harmonics are filtered spatially, using a fixed aperture, and spectrally using aluminum filters. The aluminum filters also serve the purpose of compressing the attosecond pulses, using the negative group-delay dispersion of aluminum to compensate for the intrinsic positive chirp of the attosecond pulses. This experiment demonstrates a practical method for the synthesis and control of attosecond waveforms, and in this case the production of pulses

  15. Velocity map imaging of attosecond and femtosecond dynamics in atoms and small molecules in strong laser fields

    International Nuclear Information System (INIS)

    Kling, M.F.; Ni, Yongfeng; Lepine, F.; Khan, J.I.; Vrakking, M.J.J.; Johnsson, P.; Remetter, T.; Varju, K.; Gustafsson, E.; L'Huillier, A.; Lopez-Martens, R.; Boutu, W.

    2005-01-01

    Full text: In the past decade, the dynamics of atomic and small molecular systems in strong laser fields has received enormous attention, but was mainly studied with femtosecond laser fields. We report on first applications of attosecond extreme ultraviolet (XUV) pulse trains (APTs) from high-order harmonic generation (HHG) for the study of atomic and molecular electron and ion dynamics in strong laser fields utilizing the Velocity Map Imaging Technique. The APTs were generated in argon from harmonics 13 to 35 of a 35 fs Ti:sapphire laser, and spatially and temporally overlapped with an intense IR laser field (up to 5x10 13 W/cm 2 ) in the interaction region of a Velocity Map Imaging (VMI) machine. In the VMI setup, electrons and ions that were created at the crossing point of the laser fields and an atomic or molecular beam were accelerated in a dc-electric field towards a two-dimensional position-sensitive detector, allowing to reconstruct the full initial three-dimensional velocity distribution. The poster will focus on results that were obtained for argon atoms. We recorded the velocity distribution of electron wave packets that were strongly driven in the IR laser field after their generation in Ar via single-photon ionization by attosecond XUV pulses. The 3D evolution of the electron wave packets was observed on an attosecond timescale. In addition to earlier experiments with APTs using a magnetic bottle electron time-of-flight spectrometers and with single attosecond pulses, the angular dependence of the electrons kinetic energies can give further insight into the details of the dynamics. Initial results that were obtained for molecular systems like H 2 , D 2 , N 2 , and CO 2 using the same powerful approach will be highlighted as well. We will show, that detailed insight into the dynamics of these systems in strong laser fields can be obtained (e.g. on the alignment, above-threshold ionization, direct vs. sequential two-photon ionization, dissociation, and

  16. Characterization of electron-deficient chemical bonding of diborane with attosecond electron wavepacket dynamics and laser response

    International Nuclear Information System (INIS)

    Yonehara, Takehiro; Takatsuka, Kazuo

    2009-01-01

    We report a theoretical study of non-adiabatic electrons-nuclei coupled dynamics of diborane H 2 BH 2 BH 2 under several types of short pulse lasers. This molecule is known to have particularly interesting geometrical and electronic structures, which originate from the electron-deficient chemical bondings. We revisit the chemical bonding of diborane from the view point of electron wavepacket dynamics coupled with nuclear motions, and attempt to probe the characteristics of it by examining its response to intense laser fields. We study in the following three aspects, (i) bond formation of diborane by collision between two monoboranes, (ii) attosecond electron wavepacket dynamics in the ground state and first excited state by circularly polarized laser pulse, and (iii) induced fragmentation back to monoborane molecules by linearly polarized laser. The wave lengths of two types of laser field employed are 200 nm (in UV range) and 800 nm (in IR range), and we track the dynamics from hundreds of attoseconds up to few tens of femtoseconds. To this end, we apply the ab initio semiclassical Ehrenfest theory, into which the classical vector potential of a laser field is introduced. Basic features of the non-adiabatic response of electrons to the laser fields is elucidated in this scheme. To analyze the electronic wavepackets thus obtained, we figure out bond order density that is a spatial distribution of the bond order and bond order flux density arising only from the bonding regions, and so on. Main findings in this work are: (i) dimerization of monoboranes to diborane is so efficient that even intense laser is hard to prevent it; (ii) collective motions of electron flux emerge in the central BHHB bonding area in response to the circularly polarized laser fields; (iii) laser polarization with the direction of central two BH bonding vector is efficient for the cleavage of BH 3 -BH 3 ; and (iv) nuclear derivative coupling plays a critical role in the field induced

  17. Extracting attosecond delays from spectrally overlapping interferograms

    Science.gov (United States)

    Jordan, Inga; Wörner, Hans Jakob

    2018-02-01

    Attosecond interferometry is becoming an increasingly popular technique for measuring the dynamics of photoionization in real time. Whereas early measurements focused on atomic systems with very simple photoelectron spectra, the technique is now being applied to more complex systems including isolated molecules and solids. The increase in complexity translates into an augmented spectral congestion, unavoidably resulting in spectral overlap in attosecond interferograms. Here, we discuss currently used methods for phase retrieval and introduce two new approaches for determining attosecond photoemission delays from spectrally overlapping photoelectron spectra. We show that the previously used technique, consisting in the spectral integration of the areas of interest, does in general not provide reliable results. Our methods resolve this problem, thereby opening the technique of attosecond interferometry to complex systems and fully exploiting its specific advantages in terms of spectral resolution compared to attosecond streaking.

  18. Attosecond transient absorption spectroscopy of molecular hydrogen

    International Nuclear Information System (INIS)

    Martín, Fernando; González-Castrillo, Alberto; Palacios, Alicia; Argenti, Luca; Cheng, Yan; Chini, Michael; Wang, Xiaowei; Chang, Zenghu

    2015-01-01

    We extend attosecond transient absorption spectroscopy (ATAS) to the study of hydrogen molecules, demonstrating the potential of the technique to resolve – simultaneously and with state resolution – both the electronic and nuclear dynamics. (paper)

  19. Attosecond ionization gating for isolated attosecond electron wave packet and broadband attosecond xuv pulses

    International Nuclear Information System (INIS)

    Lan Pengfei; Lu Peixiang; Cao Wei; Li Yuhua; Wang Xinlin

    2007-01-01

    An attosecond ionization gating is achieved using a few-cycle laser pulse in combination with its second harmonic. With this gating, the generation of the electron wave packet (EWP) is coherently controlled, and an isolated EWP of about 270 as is generated. An isolated broadband attosecond extreme ultraviolet pulse with a bandwidth of about 75 eV can also be generated using this gating, which can be used for EWP measurements as efficiently as a 50-as pulse, allowing one to measure a wide range of ultrafast dynamics not normally accessible before

  20. EDITORIAL: Focus on Attosecond Physics

    Science.gov (United States)

    Bandrauk, André D.; Krausz, Ferenc; Starace, Anthony F.

    2008-02-01

    Investigations of light-matter interactions and motion in the microcosm have entered a new temporal regime, the regime of attosecond physics. It is a main 'spin-off' of strong field (i.e., intense laser) physics, in which nonperturbative effects are fundamental. Attosecond pulses open up new avenues for time-domain studies of multi-electron dynamics in atoms, molecules, plasmas, and solids on their natural, quantum mechanical time scale and at dimensions shorter than molecular and even atomic scales. These capabilities promise a revolution in our microscopic knowledge and understanding of matter. The recent development of intense, phase-stabilized femtosecond (10-15 s) lasers has allowed unparalleled temporal control of electrons from ionizing atoms, permitting for the first time the generation and measurement of isolated light pulses as well as trains of pulses on the attosecond (1 as = 10-18 s) time scale, the natural time scale of the electron itself (e.g., the orbital period of an electron in the ground state of the H atom is 152 as). This development is facilitating (and even catalyzing) a new class of ultrashort time domain studies in photobiology, photochemistry, and photophysics. These new coherent, sub-fs pulses carried at frequencies in the extreme ultraviolet and soft-x-ray spectral regions, along with their intense, synchronized near-infrared driver waveforms and novel metrology based on sub-fs control of electron-light interactions, are spawning the new science of attosecond physics, whose aims are to monitor, to visualize, and, ultimately, to control electrons on their own time and spatial scales, i.e., the attosecond time scale and the sub-nanometre (Ångstrom) spatial scale typical of atoms and molecules. Additional goals for experiment are to advance the enabling technologies for producing attosecond pulses at higher intensities and shorter durations. According to theoretical predictions, novel methods for intense attosecond pulse generation may in

  1. Fundamentals of attosecond optics

    CERN Document Server

    Chang, Zenghu

    2011-01-01

    Attosecond optical pulse generation, along with the related process of high-order harmonic generation, is redefining ultrafast physics and chemistry. A practical understanding of attosecond optics requires significant background information and foundational theory to make full use of these cutting-edge lasers and advance the technology toward the next generation of ultrafast lasers. Fundamentals of Attosecond Optics provides the first focused introduction to the field. The author presents the underlying concepts and techniques required to enter the field, as well as recent research advances th

  2. Mapping the dissociative ionization dynamics of molecular nitrogen with attosecond resolution

    International Nuclear Information System (INIS)

    Klinker, M; González-Vázquez, J; Martin, F; Trabattoni, A; Sansone, G; Nisoli, M; Liu, C; Linguerri, R; Hochlaf, M; Klei, J; Vrakking, M J J; Calegari, F

    2015-01-01

    We wish to understand the processes underlying the ionization dynamics of N 2 as experimentally induced and studied by recording the kinetic energy release (KER) in a XUV-pump/IR-probe setup. To this end a theoretical model was developed describing the ionization process using Dyson Orbitals and, subsequently, the dissociation process using a large set of diabatic potential energy surfaces (PES) on which to propagate. From said set of PES, a small subset is extracted allowing for the identification of one and two photon processes chiefly responsible for the experimentally observed features. (paper)

  3. On Electron Hole Evolution in Inhomogeneous Plasmas

    Science.gov (United States)

    Kuzichev, I.; Vasko, I.; Agapitov, O. V.; Mozer, F.; Artemyev, A.

    2017-12-01

    Electron holes (EHs) are the stationary localized non-linear structures in phase space existing due to an electron population trapped within EH electrostatic potential. EHs were found to be a common phenomenon in the Earth's magnetosphere. Such structures were observed in reconnecting current sheets, injection fronts in the outer radiation belt, and in many other situations. EHs usually propagate along magnetic field lines with velocities about electron thermal velocity, are localized on the scale of about 4-10 Debye lengths, and have the field amplitude up to hundreds of mV/m. Generation of these structures, evolution, and their role in relaxation of instabilities and energy dissipation, particle energization, supporting large-scale potential drops is under active investigation. In this report, we present the results of 1.5D gyrokinetic Vlasov-Maxwell simulations of the EH evolution in plasmas with inhomogeneous magnetic field and inhomogeneous density. Our calculations show that the inhomogeneity has a critical effect on the EH dynamics. EHs propagating into stronger (weaker) magnetic field are decelerated (accelerated) with deceleration (acceleration) rate dependent on the magnetic field gradient. During the deceleration of EH, the potential drop (weak double layer) along EH is generated. Such a potential drop might be experimentally observable even for single EH in the reconnecting current sheets. The same holds for the propagation in the plasma with inhomogeneous density. For some parameters of the system, the deceleration results in the turning of the hole. The interesting feature of this process is that the turning point depends only on the EH parameters, being independent of the average inhomogeneity scale. Our calculations also demonstrate the significant difference between "quasi-particle" concept and real evolution of the hole. Indeed, the EH is accelerated (decelerated) faster than it follows from a quasi-particle energy conservation law. It indicates

  4. Attosecond physics attosecond measurements and control of physical systems

    CERN Document Server

    Torres, Ricardo; Zaïr, Amelle

    2013-01-01

    Attophysics is an emerging field in physics devoted to the study and characterization of matter dynamics in the sub-femtosecond time scale. This book gives coverage of a broad set of selected topics in this field, exciting by their novelty and their potential impact. The book is written review-like. It also includes fundamental chapters as introduction to the field for non-specialist physicists. The book is structured in four sections: basics, attosecond pulse technology, applications to measurements and control of physical processes and future perspectives. It is a valuable reference tool for researchers in the field as well as a concise introduction to non-specialist readers.

  5. Theory of attosecond delays in molecular photoionization.

    Science.gov (United States)

    Baykusheva, Denitsa; Wörner, Hans Jakob

    2017-03-28

    We present a theoretical formalism for the calculation of attosecond delays in molecular photoionization. It is shown how delays relevant to one-photon-ionization, also known as Eisenbud-Wigner-Smith delays, can be obtained from the complex dipole matrix elements provided by molecular quantum scattering theory. These results are used to derive formulae for the delays measured by two-photon attosecond interferometry based on an attosecond pulse train and a dressing femtosecond infrared pulse. These effective delays are first expressed in the molecular frame where maximal information about the molecular photoionization dynamics is available. The effects of averaging over the emission direction of the electron and the molecular orientation are introduced analytically. We illustrate this general formalism for the case of two polyatomic molecules. N 2 O serves as an example of a polar linear molecule characterized by complex photoionization dynamics resulting from the presence of molecular shape resonances. H 2 O illustrates the case of a non-linear molecule with comparably simple photoionization dynamics resulting from a flat continuum. Our theory establishes the foundation for interpreting measurements of the photoionization dynamics of all molecules by attosecond metrology.

  6. Analysis and simulation of BGK electron holes

    Directory of Open Access Journals (Sweden)

    L. Muschietti

    1999-01-01

    Full Text Available Recent observations from satellites crossing regions of magnetic-field-aligned electron streams reveal solitary potential structures that move at speeds much greater than the ion acoustic/thermal velocity. The structures appear as positive potential pulses rapidly drifting along the magnetic field, and are electrostatic in their rest frame. We interpret them as BGK electron holes supported by a drifting population of trapped electrons. Using Laplace transforms, we analyse the behavior of one phase-space electron hole. The resulting potential shapes and electron distribution functions are self-consistent and compatible with the field and particle data associated with the observed pulses. In particular, the spatial width increases with increasing amplitude. The stability of the analytic solution is tested by means of a two-dimensional particle-in-cell simulation code with open boundaries. We consider a strongly magnetized parameter regime in which the bounce frequency of the trapped electrons is much less than their gyrofrequency. Our investigation includes the influence of the ions, which in the frame of the hole appear as an incident beam, and impinge on the BGK potential with considerable energy. The nonlinear structure is remarkably resilient

  7. Connecting Lab-Based Attosecond Science with FEL research

    CERN Multimedia

    CERN. Geneva

    2011-01-01

    In the last few years laboratory-scale femtosecond laser-based research using XUV light has developed dramatically following the successful development of attosecond laser pulses by means of high-harmonic generation. Using attosecond laser pulses, studies of electron dynamics on the natural timescale that electronic processes occur in atoms, molecules and solids can be contemplated, providing unprecedented insight into the fundamental role that electrons play in photo-induced processes. In my talk I will briefly review the present status of the attosecond science research field in terms of present and foreseen capabilities, and discuss a few recent applications, including a first example of the use of attosecond laser pulses in molecular science. In addition, I will discuss very recent results of experiments where photoionization of dynamically aligned molecules is investigated using a high-harmonics XUV source. Photoionization of aligned molecules becomes all the more interesting if the experiment is perfo...

  8. Attosecond Delays in Molecular Photoionization.

    Science.gov (United States)

    Huppert, Martin; Jordan, Inga; Baykusheva, Denitsa; von Conta, Aaron; Wörner, Hans Jakob

    2016-08-26

    We report measurements of energy-dependent photoionization delays between the two outermost valence shells of N_{2}O and H_{2}O. The combination of single-shot signal referencing with the use of different metal foils to filter the attosecond pulse train enables us to extract delays from congested spectra. Remarkably large delays up to 160 as are observed in N_{2}O, whereas the delays in H_{2}O are all smaller than 50 as in the photon-energy range of 20-40 eV. These results are interpreted by developing a theory of molecular photoionization delays. The long delays measured in N_{2}O are shown to reflect the population of molecular shape resonances that trap the photoelectron for a duration of up to ∼110 as. The unstructured continua of H_{2}O result in much smaller delays at the same photon energies. Our experimental and theoretical methods make the study of molecular attosecond photoionization dynamics accessible.

  9. Plasma electron hole kinematics. I. Momentum conservation

    Energy Technology Data Exchange (ETDEWEB)

    Hutchinson, I. H.; Zhou, C. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2016-08-15

    We analyse the kinematic properties of a plasma electron hole: a non-linear self-sustained localized positive electric potential perturbation, trapping electrons, which behaves as a coherent entity. When a hole accelerates or grows in depth, ion and electron plasma momentum is changed both within the hole and outside, by an energization process we call jetting. We present a comprehensive analytic calculation of the momentum changes of an isolated general one-dimensional hole. The conservation of the total momentum gives the hole's kinematics, determining its velocity evolution. Our results explain many features of the behavior of hole speed observed in numerical simulations, including self-acceleration at formation, and hole pushing and trapping by ion streams.

  10. Assembly and application of an instrument for attosecond-time-resolved ionization chronoscopy

    International Nuclear Information System (INIS)

    Uphues, T.

    2006-11-01

    In the framework of this thesis a new setup for attosecond time-resolved measurements has been built and observations of ionization dynamics in rare gas atoms have been made. This new technique is entitled Ionization Chronoscopy and gives further evidence that time-resolved experiments in the attosecond regime will become a powerful tool for investigations in atomic physics. (orig.)

  11. Correlated nuclear and electronic dynamics in photoionized systems studied by quantum and mixed quantum-classical approaches

    International Nuclear Information System (INIS)

    Li, Zheng

    2014-09-01

    The advent of free electron lasers and high harmonic sources enables the investigation of electronic and nuclear dynamics of molecules and solids with atomic spatial resolution and femtosecond/attosecond time resolution, using bright and ultrashort laser pulses of frequency from terahertz to hard x-ray range. With the help of ultrashort laser pulses, the nuclear and electronic dynamics can be initiated, monitored and actively controlled at the typical time scale in the femtosecond to attosecond realm. Meanwhile, theoretical tools are required to describe the underlying mechanism. This doctoral thesis focuses on the development of theoretical tools based on full quantum mechanical multiconfiguration time-dependent Hartree (MCTDH) and mixed quantum classical approaches, which can be applied to describe the dynamical behavior of gas phase molecules and strongly correlated solids in the presence of ultrashort laser pulses. In the first part of this thesis, the focus is on the motion of electron holes in gas phase molecular ions created by extreme ultraviolet (XUV) photoionization and watched by spectroscopic approaches. The XUV photons create electron-hole in the valence orbitals of molecules by photoionization, the electron hole, as a positively charged quasi-particle, can then interact with the nuclei and the rest of electrons, leading to coupled non-Born-Oppenheimer dynamics. I present our study on electron-hole relaxation dynamics in valence ionized molecular ions of moderate size, using quantum wave packet and mixed quantum-classical approaches, using photoionized [H + (H 2 O) n ] + molecular ion as example. We have shown that the coupled motion of the electron-hole and the nuclei can be mapped out with femtosecond resolution by core-level x-ray transient absorption spectroscopy. Furthermore, in specific cases, the XUV photon can create a coherent electron hole, that can maintain its coherence to time scales of ∝ 1 picosecond. Employing XUV pump - IR probe

  12. Attosecond-resolved photoionization of chiral molecules.

    Science.gov (United States)

    Beaulieu, S; Comby, A; Clergerie, A; Caillat, J; Descamps, D; Dudovich, N; Fabre, B; Géneaux, R; Légaré, F; Petit, S; Pons, B; Porat, G; Ruchon, T; Taïeb, R; Blanchet, V; Mairesse, Y

    2017-12-08

    Chiral light-matter interactions have been investigated for two centuries, leading to the discovery of many chiroptical processes used for discrimination of enantiomers. Whereas most chiroptical effects result from a response of bound electrons, photoionization can produce much stronger chiral signals that manifest as asymmetries in the angular distribution of the photoelectrons along the light-propagation axis. We implemented self-referenced attosecond photoelectron interferometry to measure the temporal profile of the forward and backward electron wave packets emitted upon photoionization of camphor by circularly polarized laser pulses. We measured a delay between electrons ejected forward and backward, which depends on the ejection angle and reaches 24 attoseconds. The asymmetric temporal shape of electron wave packets emitted through an autoionizing state further reveals the chiral character of strongly correlated electronic dynamics. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  13. Coherent control of atto-second emission from aligned molecules

    Energy Technology Data Exchange (ETDEWEB)

    Boutu, W; Haessler, S; Merdji, H; Breger, P; Monchicourt, P; Carre, B; Salieres, P [CEA Saclay, DSM, Serv Photons Atomes Mol, F-91191 Gif Sur Yvette, (France); Waters, G [Univ Reading, JJ Thomson Phys Lab, Reading RG6 6AF, Berks, (United Kingdom); Stankiewicz, M [Jagiellonian Univ, Inst Phys, PL-30059 Krakow, (Poland); Frasinski, L J [Univ London Imperial Coll Sci Technol and Med, Blackett Lab, London SW7 2BW, (United Kingdom); Taieb, R; Caillat, J; Maquet, A [Univ Paris 06, UMR 7614, Lab Chim Phys Matiere Rayonnement, F-75231 Paris 05, (France); Taieb, R; Caillat, J; Maquet, A [LCPMR, UMR 7614, CNRS, F-75005 Paris, (France)

    2008-07-01

    Controlling atto-second electron wave packets and soft X-ray pulses represents a formidable challenge of general implication to many areas of science. A strong laser field interacting with atoms or molecules drives ultrafast intra-atomic/molecular electron wave packets on a sub femtosecond timescale, resulting in the emission of atto-second bursts of extreme-ultraviolet light. Controlling the intra-atomic/molecular electron dynamics enables steering of the atto-second emission. Here, we carry out a coherent control in linear molecules, where the interaction of the laser-driven electron wave packet with the core leads to quantum interferences. We demonstrate that these interferences can be finely controlled by turning the molecular axis relative to the laser polarization, that is, changing the electron re-collision angle. The wave-packet coulombic distortion modifies the spectral phase jump measured in the extreme-ultraviolet emission. Our atto-second control of the interference results in atto-second pulse shaping, useful for future applications in ultrafast coherent control of atomic and molecular processes. (authors)

  14. Multiphoton Processes and Attosecond Physics

    CERN Document Server

    Midorikawa, Katsumi; 12th International Conference on Multiphoton Processes; 3rd International Conference on Attosecond Physics

    2012-01-01

    Recent advances in ultrashort pulsed laser technology have opened new frontiers in atomic, molecular and optical sciences. The 12th International Conference on Multiphoton Processes (ICOMP12) and the 3rd International Conference on Attosecond Physics (ATTO3), held jointly in Sapporo, Japan, during July 3-8, showcased studies at the forefront of research on multiphoton processes and attosecond physics. This book summarizes presentations and discussions from these two conferences.

  15. Reconstruction of Attosecond Pulse Trains

    Science.gov (United States)

    Mairesse, Y.; Agostini, P.; Breger, P.; Carre, B.; Merdji, A.; Monchicourt, P.; Salieres, P.; Varju, K.; Gustafsson, E.; Johnsson, P.; Mauritsson, J.; Remetter, T.; L'Huillier, A.; Frasinski, L. J.

    2006-11-01

    We show that it is possible to completely reconstruct the intensity profile of the attosecond bursts emitted as a superposition of high harmonics from a series of RABBIT measurements carried out at different infrared intensities. The electric field can be recovered from a measurement of the central harmonic chirp. Timing, chirp and variations of the carrier-to-envelope phase of the attosecond bursts are accessible to the proposed method.

  16. Attosecond photoelectron spectroscopy of electron transport in solids

    International Nuclear Information System (INIS)

    Magerl, Elisabeth

    2011-01-01

    Time-resolved photoelectron spectroscopy of condensed matter systems in the attosecond regime promises new insights into excitation mechanisms and transient dynamics of electrons in solids. This timescale became accessible directly only recently with the development of the attosecond streak camera and of laser systems providing few-cycle, phase-controlled laser pulses in the near-infrared, which are used to generate isolated, sub-femtosecond extreme-ultraviolet pulses with a well-defined timing with respect to the near-infrared pulse. Employing these pulses, the attosecond streak camera offers time resolutions as short as a few 10 attoseconds. In the framework of this thesis, a new, versatile experimental apparatus combining attosecond pulse generation in gases with state of the art surface science techniques is designed, constructed, and commissioned. Employing this novel infrastructure and the technique of the attosecond transient recorder, we investigate transport phenomena occurring after photoexcitation of electrons in tungsten and rhenium single crystals and show that attosecond streaking is a unique method for resolving extremely fast electronic phenomena in solids. It is demonstrated that electrons originating from different energy levels, i.e. from the conduction band and the 4f core level, are emitted from the crystal surface at different times. The origin of this time delay, which is below 150 attoseconds for all studied systems, is investigated by a systematic variation of several experimental parameters, in particular the photon energy of the employed attosecond pulses. These experimental studies are complemented by theoretical studies of the group velocity of highly-excited electrons based on ab initio calculations. While the streaking technique applied on single crystals can provide only information about the relative time delay between two types of photoelectrons, the absolute transport time remains inaccessible. We introduce a scheme of a reference

  17. Attosecond photoelectron spectroscopy of electron transport in solids

    Energy Technology Data Exchange (ETDEWEB)

    Magerl, Elisabeth

    2011-03-31

    Time-resolved photoelectron spectroscopy of condensed matter systems in the attosecond regime promises new insights into excitation mechanisms and transient dynamics of electrons in solids. This timescale became accessible directly only recently with the development of the attosecond streak camera and of laser systems providing few-cycle, phase-controlled laser pulses in the near-infrared, which are used to generate isolated, sub-femtosecond extreme-ultraviolet pulses with a well-defined timing with respect to the near-infrared pulse. Employing these pulses, the attosecond streak camera offers time resolutions as short as a few 10 attoseconds. In the framework of this thesis, a new, versatile experimental apparatus combining attosecond pulse generation in gases with state of the art surface science techniques is designed, constructed, and commissioned. Employing this novel infrastructure and the technique of the attosecond transient recorder, we investigate transport phenomena occurring after photoexcitation of electrons in tungsten and rhenium single crystals and show that attosecond streaking is a unique method for resolving extremely fast electronic phenomena in solids. It is demonstrated that electrons originating from different energy levels, i.e. from the conduction band and the 4f core level, are emitted from the crystal surface at different times. The origin of this time delay, which is below 150 attoseconds for all studied systems, is investigated by a systematic variation of several experimental parameters, in particular the photon energy of the employed attosecond pulses. These experimental studies are complemented by theoretical studies of the group velocity of highly-excited electrons based on ab initio calculations. While the streaking technique applied on single crystals can provide only information about the relative time delay between two types of photoelectrons, the absolute transport time remains inaccessible. We introduce a scheme of a reference

  18. Atto-second control of collective electron motion in plasmas

    International Nuclear Information System (INIS)

    Borot, Antonin; Malvache, Arnaud; Chen, Xiaowei; Jullien, Aurelie; Lopez-Martens, Rodrigo; Geindre, Jean-Paul; Audebert, Patrick; Mourou, Gerard; Quere, Fabien

    2012-01-01

    Today, light fields of controlled and measured waveform can be used to guide electron motion in atoms and molecules with atto-second precision. Here, we demonstrate atto-second control of collective electron motion in plasmas driven by extreme intensity (approximate to 10 18 W cm -2 ) light fields. Controlled few-cycle near-infrared waves are tightly focused at the interface between vacuum and a solid-density plasma, where they launch and guide sub-cycle motion of electrons from the plasma with characteristic energies in the multi-kilo-electron-volt range-two orders of magnitude more than has been achieved so far in atoms and molecules. The basic spectroscopy of the coherent extreme ultraviolet radiation emerging from the light-plasma interaction allows us to probe this collective motion of charge with sub-200 as resolution. This is an important step towards atto-second control of charge dynamics in laser-driven plasma experiments. (authors)

  19. Attosecond experiments on plasmonic nanostructures principles and experiments

    CERN Document Server

    Schötz, Johannes

    2016-01-01

    Johannes Schötz presents the first measurements of optical electro-magnetic near-fields around nanostructures with subcycle-resolution. The ability to measure and understand light-matter interactions on the nanoscale is an important component for the development of light-wave-electronics, the control and steering of electron dynamics with the frequency of light, which promises a speed-up by several orders of magnitude compared to conventional electronics. The experiments presented here on metallic nanotips, widely used in experiments and applications, do not only demonstrate the feasibility of attosecond streaking as a unique tool for fundamental studies of ultrafast nanophotonics but also represent a first important step towards this goal. Contents Electron Scattering in Solids Attosecond Streaking from Metal Nanotips Target Groups Lecturers and students of physics, especially in the area of nanophotonics and attosecond physics About the Author Johannes Schötz received his Master's degree in physics and cu...

  20. Decoherence in attosecond photoionization.

    Science.gov (United States)

    Pabst, Stefan; Greenman, Loren; Ho, Phay J; Mazziotti, David A; Santra, Robin

    2011-02-04

    The creation of superpositions of hole states via single-photon ionization using attosecond extreme-ultraviolet pulses is studied with the time-dependent configuration-interaction singles (TDCIS) method. Specifically, the degree of coherence between hole states in atomic xenon is investigated. We find that interchannel coupling not only affects the hole populations, but it also enhances the entanglement between the photoelectron and the remaining ion, thereby reducing the coherence within the ion. As a consequence, even if the spectral bandwidth of the ionizing pulse exceeds the energy splittings among the hole states involved, perfectly coherent hole wave packets cannot be formed. For sufficiently large spectral bandwidth, the coherence can only be increased by increasing the mean photon energy.

  1. Attosecond interference control of XUV photoionization

    Energy Technology Data Exchange (ETDEWEB)

    Cao Wei; Lu Peixiang; Lan Pengfei; Li Yuhua; Wang Xinlin [Wuhan National Laboratory for Optoelectronics and School of Optoelectronics Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)], E-mail: lupeixiang@mail.hust.edu.cn

    2008-04-28

    The characterizing of attosecond pulses has great importance for the investigation of ultrafast phenomena. Here, we proposed a novel and efficient scheme for measuring attosecond XUV pulses, which is based on laser-dressed XUV photoionization. The ultrashort attosecond gating of photoionization leads to an interference structure in the photoelectron spectrum. Then the duration of the attosecond XUV pulse can be retrieved directly from the photoelectron spectrum with a rather high resolution.

  2. Attosecond interference control of XUV photoionization

    International Nuclear Information System (INIS)

    Cao Wei; Lu Peixiang; Lan Pengfei; Li Yuhua; Wang Xinlin

    2008-01-01

    The characterizing of attosecond pulses has great importance for the investigation of ultrafast phenomena. Here, we proposed a novel and efficient scheme for measuring attosecond XUV pulses, which is based on laser-dressed XUV photoionization. The ultrashort attosecond gating of photoionization leads to an interference structure in the photoelectron spectrum. Then the duration of the attosecond XUV pulse can be retrieved directly from the photoelectron spectrum with a rather high resolution

  3. Measurement and Control of Attosecond Pulses

    Science.gov (United States)

    2016-04-25

    highest power or the shortest duration attosecond pulses. Results: We have adapted the attosecond lighthouse to gases and confirmed isolated...simplifying attosecond metrology so it becomes more widely accessible. Result: This goal was completely accomplished. Aim 2: To exploit few- cycle ...μm driver. Aim 3: To compare attosecond gating methods, selecting the most efficient way to produce the highest power or the shortest duration

  4. Electron-hole liquid in semiconductors and low-dimensional structures

    Science.gov (United States)

    Sibeldin, N. N.

    2017-11-01

    The condensation of excitons into an electron-hole liquid (EHL) and the main EHL properties in bulk semiconductors and low-dimensional structures are considered. The EHL properties in bulk materials are discussed primarily in qualitative terms based on the experimental results obtained for germanium and silicon. Some of the experiments in which the main EHL thermodynamic parameters (density and binding energy) have been obtained are described and the basic factors that determine these parameters are considered. Topics covered include the effect of external perturbations (uniaxial strain and magnetic field) on EHL stability; phase diagrams for a nonequilibrium exciton-gas-EHL system; information on the size and concentration of electron-hole drops (EHDs) under various experimental conditions; the kinetics of exciton condensation and of recombination in the exciton-gas-EHD system; dynamic EHD properties and the motion of EHDs under the action of external forces; the properties of giant EHDs that form in potential wells produced by applying an inhomogeneous strain to the crystal; and effects associated with the drag of EHDs by nonequilibrium phonons (phonon wind), including the dynamics and formation of an anisotropic spatial structure of the EHD cloud. In discussing EHLs in low-dimensional structures, a number of studies are reviewed on the observation and experimental investigation of phenomena such as spatially indirect (dipolar) electron-hole and exciton (dielectric) liquids in GaAs/AlGaAs structures with double quantum wells (QWs), EHDs containing only a few electron-hole pairs (dropletons), EHLs in type-I silicon QWs, and spatially direct and dipolar EHLs in type-II silicon-germanium heterostructures.

  5. Electron-hole drop (EHD) stability in deformation potential well

    International Nuclear Information System (INIS)

    Makarov, A.G.; Tikhodeev, S.G.

    1984-01-01

    In heterogeneously-deformed Ge the stability of electron-hole droplets (EHD) being in a potential well is considered. It is shown that the potential well effect is equivalent to the decrease of effective density of phonon EHD charge. It is pointed out that heating EHD (for example, by IR radiation), can increase the phonon droplet charge and affect its stability

  6. Interaction between Electron Holes in a Strongly Magnetized Plasma

    DEFF Research Database (Denmark)

    Lynov, Jens-Peter; Michelsen, Poul; Pécseli, Hans

    1980-01-01

    The interaction between electron holes in a strongly magnetized, plasma-filled waveguide is investigated by means of computer simulation. Two holes may or may not coalesce, depending on their amplitudes and velocities. The interaction between holes and Trivelpiece-Gould solitons is demonstrated...

  7. Quantum simulations of small electron-hole complexes

    International Nuclear Information System (INIS)

    Lee, M.A.; Kalia, R.K.; Vashishta, P.D.

    1984-09-01

    The Green's Function Monte Carlo method is applied to the calculation of the binding energies of electron-hole complexes in semiconductors. The quantum simulation method allows the unambiguous determination of the ground state energy and the effects of band anisotropy on the binding energy. 22 refs., 1 fig

  8. Spectral Caustics in Attosecond Science

    Directory of Open Access Journals (Sweden)

    Dudovich N.

    2013-03-01

    Full Text Available A unique type of singularity common in wave phenomena, known as caustics, links processes observed in many different branches of physics [1]. We investigate the role of caustics in attosecond science and in particular the physical process behind high harmonic generation. By exploiting singularities of the three-step model that describes HHG, we can manipulate and enhance specific features in the emitted harmonic spectrum. This new level of control holds promises in both scientific and technological aspects of attosecond science, and provides a deeper insight into the basic mechanism underlying the high harmonic generation process.

  9. Next Generation Driver for Attosecond and Laser-plasma Physics.

    Science.gov (United States)

    Rivas, D E; Borot, A; Cardenas, D E; Marcus, G; Gu, X; Herrmann, D; Xu, J; Tan, J; Kormin, D; Ma, G; Dallari, W; Tsakiris, G D; Földes, I B; Chou, S-W; Weidman, M; Bergues, B; Wittmann, T; Schröder, H; Tzallas, P; Charalambidis, D; Razskazovskaya, O; Pervak, V; Krausz, F; Veisz, L

    2017-07-12

    The observation and manipulation of electron dynamics in matter call for attosecond light pulses, routinely available from high-order harmonic generation driven by few-femtosecond lasers. However, the energy limitation of these lasers supports only weak sources and correspondingly linear attosecond studies. Here we report on an optical parametric synthesizer designed for nonlinear attosecond optics and relativistic laser-plasma physics. This synthesizer uniquely combines ultra-relativistic focused intensities of about 10 20  W/cm 2 with a pulse duration of sub-two carrier-wave cycles. The coherent combination of two sequentially amplified and complementary spectral ranges yields sub-5-fs pulses with multi-TW peak power. The application of this source allows the generation of a broad spectral continuum at 100-eV photon energy in gases as well as high-order harmonics in relativistic plasmas. Unprecedented spatio-temporal confinement of light now permits the investigation of electric-field-driven electron phenomena in the relativistic regime and ultimately the rise of next-generation intense isolated attosecond sources.

  10. Generation and Characterization of Attosecond Pulses

    Energy Technology Data Exchange (ETDEWEB)

    Ian A. Walmsley; Robert W. Boyd

    2006-04-24

    The research undertaken in this project has been directed toward the area of attoscience, in particular the problem of attosecond metrology. That is, the accurate determination of the electric field of attosecond XUV radiation. This outstanding problem has been identified as a critical technology for further development of the field, and our research adds to the area by providing the first method for characterization using the harmonic radiation itself as a tool. The technical effectiveness of this approach is very high, since it is vastly easier to detect XUV radiation directly than via the spectrum of photoelectrons liberated from atoms by it. This means that the experimental data rate can be much higher in principle using all-optical detection that electron detection, which will greatly aid the utility of harmonic XUV sources in attoscience applications. There are as yet no direct public benefits from this area of scientific research, though access to material structural dynamics on unprecedented brief timescales are expected to yield significant benefits for the future.

  11. Desorption by Femtosecond Laser Pulses : An Electron-Hole Effect?

    OpenAIRE

    D. M., NEWNS; T. F., HEINZ; J. A., MISEWICH; IBM Research Division, T. J. Watson Research Center; IBM Research Division, T. J. Watson Research Center; IBM Research Division, T. J. Watson Research Center

    1992-01-01

    Desorption of molecules from metal surfaces induced by femtosecond visible laser pulses has been reported. Since the lattice temperature rise is insufficient to explain desorption, an electronic mechanism is clearly responsible. It is shown that a theory based on direct coupling between the center-of-mass degree of freedom of the adsorbate and the electron-hole excitations of the substrate provides a satisfactory explanation of the various experimental findings.

  12. Theory of strong-field attosecond transient absorption

    International Nuclear Information System (INIS)

    Wu, Mengxi; Chen, Shaohao; Camp, Seth; Schafer, Kenneth J; Gaarde, Mette B

    2016-01-01

    Attosecond transient absorption is one of the promising new techniques being developed to exploit the availability of sub-femtosecond extreme ultraviolet (XUV) pulses to study the dynamics of the electron on its natural time scale. The temporal resolution in a transient absorption setup comes from the control of the relative delay and coherence between pump and probe pulses, while the spectral resolution comes from the characteristic width of the features that are being probed. In this review we focus on transient absorption scenarios where an attosecond pulse of XUV radiation creates a broadband excitation that is subsequently probed by a few cycle infrared (IR) laser. Because the attosecond XUV pulses are locked to the IR field cycle, the exchange of energy in the laser–matter interaction can be studied with unprecedented precision. We focus on the transient absorption by helium atoms of XUV radiation around the first ionization threshold, where we can simultaneoulsy solve the time-dependent Schrödinger equation for the single atom response and the Maxwell wave equation for the collective response of the nonlinear medium. We use a time-domain method that allows us to treat on an equal footing all the different linear and nonlinear processes by which the medium can exchange energy with the fields. We present several simple models, based on a few-level system interacting with a strong IR field, to explain many of the novel features found in attosecond transient absorption spectrograms. These include the presence of light-induced states, which demonstrate the ability to probe the dressed states of the atom. We also present a time-domain interpretation of the resonant pulse propagation features that appear in absorption spectra in dense, macroscopic media. We close by reviewing several recent experimental results that can be explained in terms of the models we discuss. Our aim is to present a road map for understanding future attosecond transient absorption

  13. Attosecond pulse trains generated using two color laser fields

    International Nuclear Information System (INIS)

    Mauritsson, J.; Louisiana State University, Baton Rouge, LA; Johnsson, P.; Gustafsson, E.; L'Hullier, A.; Schafer, K.J.; Gaarde, M.B.

    2006-01-01

    parameters trains of attosecond pulses with only one pulse per IR cycle are generated. The presence of one attosecond pulse per IR cycle may furthermore be taken as evidence that consecutive pulses in the train have the same carrier envelope phase. When the attosecond pulses interact with a gas of atoms, electron wave packets are created if the photon energy exceeds the ionization potential. The wave packets are temporally localized with properties that are directly inherited from the attosecond pulses. If the ionization takes place in the presence of a strong IR field an energy exchange between the electrons and the field occurs. The amount of energy exchanged depends on the timing with respect to the phase of the IR field when the electrons are injected into the the continuum. Using trains with only one pulse per IR cycle, all the wave packets are injected with the same timing with respect to the IR field, thus enabling us to measure their dynamics in the dressed continuum. Using a velocity map imaging spectrometer we can measure a projection of the three dimensional electron distributions.

  14. Génération d'impulsions attosecondes sur miroir plasma à très haute cadence

    OpenAIRE

    Borot , Antonin

    2012-01-01

    Focusing an intense laser pulse onto a solid surface leads to the almost complete ionisation of matter and the creation of a plasma of near-solid electronic density. Collective charge dynamic of the plasma electrons is then driven by the laser field and can give birth to a train of XUV attosecond pulses. This work aims at demonstrating that plasma dynamics can be driven with attosecond precison by the laser field in order to generate reproducible attosecond XUV pulses. Therfore we built up th...

  15. Correlation effects on spin-polarized electron-hole quantum bilayer

    Energy Technology Data Exchange (ETDEWEB)

    Saini, L. K., E-mail: drlalitsaini75@gmail.com; Sharma, R. O., E-mail: sharmarajesh0387@gmail.com [Department of Applied Physics, S. V. National Institute of Technology, Surat – 395 007 (India); Nayak, Mukesh G. [Department of Physics, Silvassa College (Silvassa Institute of Higher Learning), Silvassa 396 230 (India)

    2016-05-06

    We present a numerical calculation for the intra- and interlayer pair-correlation functions, g{sub ll’}(r), of spin-polarized electron-hole quantum bilayers at zero temperature. The calculations of g{sub ll’}(r) are performed by including electron correlations within the dynamical version of the self-consistent mean-field approximation of Singwi, Tosi, Land and Sjölander (qSTLS). Our study reveals that the critical layer density decreases (increases) due to the inclusion of finite width (mass-asymmetry) effect during the phase-transition from charge-density wave to Wigner crystal ground-state by yielding the pronounced oscillatory behavior ing{sub ll}(r). The results are compared with recent findings of spin-polarized electron-hole quantum bilayers with mass-symmetry and zero width effects. To highlight the importance of dynamical character of correlations, we have also compared our results with the STLS results.

  16. Electron Hole Plasma in Solids Induced by Ultrashort XUV Laser Pulses

    International Nuclear Information System (INIS)

    Rethfeld, B.; Medvedev, N.

    2013-01-01

    Irradiation of solids with ultrashort XUV laser pulses leads to an excitation of electrons from the valence band and deeper shells to the conduction band leading to a nonequilibrium highly energetic electron hole plasma. We investigate the transient electron dynamics in a solid semiconductor and metal (silicon and aluminum, respectively) under irradiation with a femtosecond VUV to XUV laser pulse as used in experiments with the Free Electron Laser FLASH at DESY in Hamburg, Germany. Applying the Asymptotical Trajectory Monte-Carlo technique, we obtain the transient energy distribution of the excited and ionized electrons within the solid. Photon absorption by electrons in different bands and secondary excitation and ionization processes are simulated event by event. The method was extended in order to take into account the electronic band structure and Pauli's principle for electrons in the conduction band. In this talk we review our results on the dynamics of the transient electron-hole plasma, in particular its transient density and energy distribution in dependence on laser and material parameters. For semiconductors we introduce the concept of an ''effective energy gap'' for collective electronic excitation, which can be applied to estimate the free electron density after high-intensity ultrashort XUV laser pulse irradiation. For aluminum we demonstrate that the electronic spectra depend on the relaxation kinetics of the excited electronic subsystem. Experimentally observed spectra of emitted photons from irradiated aluminum can be explained well with our results. (author)

  17. Attosecond electron wave packet interferometry

    International Nuclear Information System (INIS)

    Remetter, T.; Ruchon, T.; Johnsson, P.; Varju, K.; Gustafsson, E.

    2006-01-01

    Complete test of publication follows. The well controlled generation and characterization of attosecond XUV light pulses provide an unprecedented tool to study electron wave packets (EWPs). Here a train of attosecond pulses is used to create and study the phase of an EWP in momentum space. There is a clear analogy between electronic wave functions and optical fields. In optics, methods like SPIDER or wave front shearing interferometry, allow to measure the spectral or spatial phase of a light wave. These two methods are based on the same principle: an interferogram is produced when recombining two sheared replica of a light pulse, spectrally (SPIDER) or spatially (wave front shearing interferometry). This enables the comparison of two neighbouring different spectral or spatial slices of the original wave packet. In the experiment, a train of attosecond pulses is focused in an Argon atomic gas jet. EWPs are produced from the single XUV photon ionization of Argon atoms. If an IR beam is synchronized to the EWPs, it is possible to introduce a shear in momentum space between two consecutive s wave packets. A Velocity Map Imaging Spectrometer (VMIS) enables us to detect the interference pattern. An analysis of the interferograms will be presented leading to a conclusion about the symmetry of the studied wave packet.

  18. Nondipole effects in attosecond photoelectron streaking

    DEFF Research Database (Denmark)

    Spiewanowski, Maciek; Madsen, Lars Bojer

    2012-01-01

    The influence of nondipole terms on the time delay in photoionization by an extreme-ultraviolet attosecond pulse in the presence of a near-infrared femtosecond laser pulse from 1s, 2s, and 2p states in hydrogen is investigated. In this attosecond photoelectron streaking process, the relative...

  19. Theory of magnetostriction of electron-hole drops in Ge

    International Nuclear Information System (INIS)

    Markiewicz, R.S.

    1978-01-01

    A large mass of electron-hole liquid (γ drop) formed in a strain-induced potential well in Ge is known to distort its shape significantly in a magnetic field B > or approx. = 1 kG. It is shown in this paper that the shape change can be understood in detail as due to a ''recombination current'' of electron-hole pairs needed to replace those pairs which recombine in the drop volume. The Lorentz force deflects this current and produces a macroscopic dipole current loop inside the drop. The drop then changes shape to minimize its total energy, including magnetic, strain, and surface energies. While the drop usually flattens along the field direction, both para- and diamagnetic effects (elongated drops) are found to be possible, depending on excitation conditions, in accord with experiment. Similar effects are predicted to occur in small drops in unstrained Ge. This paper presents a magnetohydrodynamic theory of the magnetostriction which takes into account density variations which occur in the strain well and in high magnetic fields. A simpler theory is given for the special case in which the drop may be considered incompressible (small drops and moderate fields). Effects of carrier mass anisotropy and fluid viscosity are taken into consideration

  20. Electron holes observed in the Moon Plasma Wake

    Science.gov (United States)

    Hutchinson, I. H.; Malaspina, D.; Zhou, C.

    2017-10-01

    Electrostatic instabilities are predicted in the magnetized wake of plasma flowing past a non-magnetic absorbing object such as a probe or the moon. Analysis of the data from the Artemis satellites, now orbiting the moon at distances ten moon radii and less, shows very clear evidence of fast-moving isolated solitary potential structures causing bipolar electric field excursions as they pass the satellite's probes. These structures have all the hallmarks of electron holes: BGK solitons typically a few Debye-lengths in size, self-sustaining by a deficit of phase-space density on trapped orbits. Electron holes are now observed to be widespread in space plasmas. They have been observed in PIC simulations of the moon wake to be the non-linear consequence of the predicted electron instabilities. Simulations document hole prevalence, speed, length, and depth; and theory can explain many of these features from kinetic analysis. The solar wind wake is certainly the cause of the overwhelming majority of the holes observed by Artemis, because we observe almost all holes to be in or very near to the wake. We compare theory and simulation of the hole generation, lifetime, and transport mechanisms with observations. Work partially supported by NASA Grant NNX16AG82G.

  1. Attosecond physics at the nanoscale

    Czech Academy of Sciences Publication Activity Database

    Ciappina, Marcelo F.; Perez-Hernandez, J.A.; Landsman, A.S.; Okell, W.A.; Zherebtsov, S.; Foerg, B.; Schoetz, J.; Seiffert, L.; Fennel, T.; Shaaran, T.; Zimmermann, T.; Chacon, A.; Guichard, R.; Zair, A.; Tisch, J.W.G.; Marangos, J.P.; Witting, T.; Braun, A.; Maier, S. A.; Roso, L.; Krueger, M.; Hommelhoff, P.; Kling, M.F.; Krausz, F.; Lewenstein, M.

    2017-01-01

    Roč. 80, č. 5 (2017), 1-50, č. článku 054401. ISSN 0034-4885 R&D Projects: GA MŠk EF15_008/0000162; GA MŠk LQ1606 Grant - others:ELI Beamlines(XE) CZ.02.1.01/0.0/0.0/15_008/0000162 Institutional support: RVO:68378271 Keywords : attosecond physics * plasmonic fields * strong field physics Subject RIV: BH - Optics, Masers, Laser s OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 14.311, year: 2016

  2. Temporal Talbot effect in propagation of attosecond electron waves

    International Nuclear Information System (INIS)

    Varro, S.

    2010-01-01

    Complete text of publication follows. The rapid development in extreme strong-field and extreme short-pulse laser physics provide us with many potentials to explore the dynamics of fundamental processes taking place in light-matter interactions and in propagation of electromagnetic or matter waves. The present paper discusses the propagation of above-threshold electron waves generated by (not necessary ultra-short) strong laser fields. Recently we have shown that - in analogy with the formation of attosecond light pulses by interference of high-order harmonics - the wave components of photoelectrons are naturally assembled in attosecond spikes, through the Fourier synthesis of these de Broglie waves. We would like to emphasize that the proposed scheme does not presupposes an a priori ultrashort excitation. Owing to the inherent dispersion of electron waves even in vacuum, the clean attosecond structure (emanating perpendicularly from a metal target surface) is gradually spoiled due to destructive interference. Fortunately the collapsed fine structure recovers itself at certain distances from the source within well-defined 'revival layers'. This is a temporal analogon of the optical Talbot effect representing the self-imaging of a grating, which is illuminated by stationary plane waves, in the near field. The 'collaps bands' and the 'revival layers' introduced in ref. 3 have been found merely on the basis of some attosecond layers turned out to show certain regularities. In the meantime we have derived approximate analytic formulae for the propagation characteristics, with the help of which we can keep track of the locations of the 'collaps bands' and the 'revival layers' on a larger scale. We shall report on these semiclassical results, and also discuss their possible connection with the recently found entropy remnants in multiphoton Compton scattering by electronic wave packets. Acknowledgement. This work has been supported by the Hungarian National Scientific

  3. Luminescence of high density electron-hole plasma in CdS and CdSe in a wide temperature range

    International Nuclear Information System (INIS)

    Yoshida, H.; Shionoya, S.

    1983-01-01

    Time-resolved spectra of the spontaneous luminescence of the high density electron-hole plasma (EHP) in CdS and CdSe are observed in a wide range of temperature which is surely higher than the calculated critical temperature for electron-hole liquid formation, in order to carry forward discussion on dynamic nature of the EHP previously observed in 4.2 K experiments. Spectra in the late stage are analyzed, and obtained values of the reduced bandgap energy and chemical potential are compared with those theoretically calculated for higher temperatures. The aspects of the change of the spectral shape in the late stage are hard to understand. Unfortunately no clear conclusion is drawn on the nature of the EHP produced at 4.2 K. The only thing one can say is that the condensed electron-hole liquid state, which is in equilibrium with the exciton state, is not realized. (author)

  4. Theory of attosecond absorption spectroscopy in krypton

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Lindroth, Eva; Madsen, Lars Bojer

    2012-01-01

    A theory for time-domain attosecond pump–attosecond probe photoabsorption spectroscopy is formulated and related to the atomic response. The theory is illustrated through a study of attosecond absorption spectroscopy in krypton. The atomic parameters entering the formulation such as energies...... of the hole in this manner. In a second example, a hole is created in an inner shell by the first pulse, and the second probe pulse couples an even more tightly bound state to that hole. The hole decays in this example by Auger electron emission, and the absorption spectroscopy follows the decay of the hole...

  5. Energy of ground state of laminar electron-hole liquid

    International Nuclear Information System (INIS)

    Andryushin, E.A.

    1976-01-01

    The problem of a possible existence of metal electron-hole liquid in semiconductors is considered. The calculation has been carried out for the following model: two parallel planes are separated with the distance on one of the planes electrons moving, on the other holes doing. Transitions between the planes are forbidden. The density of particles for both planes is the same. The energy of the ground state and correlation functions for such electron-and hole system are calculated. It is shown that the state of a metal liquid is more advantageous against the exciton gas. For the mass ratio of electrons and holes, msub(e)/msub(h) → 0 a smooth rearrangement of the system into a state with ordered heavy particles is observed

  6. Electromagnetic interactions in an electron-hole plasma

    International Nuclear Information System (INIS)

    1977-01-01

    Certain problems electromagnetic interactions both of external SHF radiation with an electron-hole (eh) plasma and in the plasma itself are considered. The production and properties of a non-equilibrium eh plasma in semiconductors, pinch effect in a plasma of solids, strong electric fields in a plasma of inhomogeneous semiconductors and heat effects in a semiconductor plasma are discussed. The influence of a surface, kinetics of recombination processes in the semiconductor volume and the plasma statistics the spatial distribution of carriers, current characteristics and plasma recombination radiation under the conditions of pinch effect is described. The diagnostics methods of the phenomena are presented. The behaviour of diode structures with pn transitions in strong SHF fields is discussed. Special attention is paid to collective phenomena in the plasma of semiconductor devices and the variation of carrier density in strong fields. The appearance of electromotive force in inhomogeneous diode structures placed in strong SHF fields is considered

  7. Many-particle correlations in quasi-two-dimensional electron-hole systems

    International Nuclear Information System (INIS)

    Nikolaev, Valentin

    2002-01-01

    This thesis reports a theoretical investigation of many-particle correlation effects in semiconductor heterostructures containing quantum wells. Particular attention is paid towards quasi-particle pair correlations. Using the Green's function technique and the ladder approximation as a basis, the generalized mass action law, which describes the redistribution of particles between correlated and uncorrelated states in quasi-two-dimensional systems for different temperatures and total densities, is derived. The expression is valid beyond the low-density limit, which allows us to investigate the transition of the system from a dilute exciton gas to a dense electron-hole plasma. A generalized Levinson theorem, which takes k-space filling into account, is formulated. Screening in quasi-two-dimensional systems is analyzed rigorously. Firstly, the qualitatively new mechanism of static local screening by indirect excitons is studied using the simple Thomas-Fermi approximation. Then, a detailed many-body description suitable for a proper account of dynamic screening by a quasi-2D electron-hole plasma, and consistent with the previously derived mass action law, is provided. The generalized Lindhard approximation and excitonic plasmon-pole approximations are also derived. The theory is applied to single and double quantum wells. A self-consistent procedure is developed for numerical investigation of the ionization degree of an electron-hole plasma at different values of temperature/exciton Rydberg ratios. This procedure accounts for screening, k-space filling (exciton bleaching), and the formation of excitons. An abrupt jump in the value of the ionization degree that happens with an increase of the carrier density or temperature (Mott transition) is found in a certain density-temperature region. It has been found that the critical density of the Mott transition for indirect excitons may be much smaller than that for direct excitons. A suggestion has been made that some of the

  8. Laser-plasma accelerator-based single-cycle attosecond undulator source

    Science.gov (United States)

    Tibai, Z.; Tóth, Gy.; Nagyváradi, A.; Sharma, A.; Mechler, M. I.; Fülöp, J. A.; Almási, G.; Hebling, J.

    2018-06-01

    Laser-plasma accelerators (LPAs), producing high-quality electron beams, provide an opportunity to reduce the size of free-electron lasers (FELs) to only a few meters. A complete system is proposed here, which is based on FEL technology and consists of an LPA, two undulators, and other magnetic devices. The system is capable to generate carrier-envelope phase stable attosecond pulses with engineered waveform. Pulses with up to 60 nJ energy and 90-400 attosecond duration in the 30-120 nm wavelength range are predicted by numerical simulation. These pulses can be used to investigate ultrafast field-driven electron dynamics in matter.

  9. Diffusive scattering of electrons by electron holes around injection fronts

    Science.gov (United States)

    Vasko, I. Y.; Agapitov, O. V.; Mozer, F. S.; Artemyev, A. V.; Krasnoselskikh, V. V.; Bonnell, J. W.

    2017-03-01

    Van Allen Probes have detected nonlinear electrostatic spikes around injection fronts in the outer radiation belt. These spikes include electron holes (EH), double layers, and more complicated solitary waves. We show that EHs can efficiently scatter electrons due to their substantial transverse electric fields. Although the electron scattering driven by EHs is diffusive, it cannot be evaluated via the standard quasi-linear theory. We derive analytical formulas describing local electron scattering by a single EH and verify them via test particle simulations. We show that the most efficiently scattered are gyroresonant electrons (crossing EH on a time scale comparable to the local electron gyroperiod). We compute bounce-averaged diffusion coefficients and demonstrate their dependence on the EH spatial distribution (latitudinal extent and spatial filling factor) and individual EH parameters (amplitude of electrostatic potential, velocity, and spatial scales). We show that EHs can drive pitch angle scattering of ≲5 keV electrons at rates 10-2-10-4 s-1 and, hence, can contribute to electron losses and conjugated diffuse aurora brightenings. The momentum and pitch angle scattering rates can be comparable, so that EHs can also provide efficient electron heating. The scattering rates driven by EHs at L shells L ˜ 5-8 are comparable to those due to chorus waves and may exceed those due to electron cyclotron harmonics.

  10. Generation of atto-second pulses in atoms and molecules

    International Nuclear Information System (INIS)

    Haessler, St.

    2009-12-01

    When a low-frequency laser pulse is focused to a high intensity into a gas, the electric field of the laser light may become of comparable strength to that felt by the electrons bound in an atom or molecule. A valence electron can then be 'freed' by tunnel ionization, accelerated by the strong oscillating laser field and can eventually re-collide and recombine with the ion. The gained kinetic energy is then released as a burst of coherent X-UV light and the macroscopic gas medium then becomes a source of X-UV light pulses of atto-second (1 as equals 10 -18 s) duration. This is the natural time-scale of electron dynamics in atoms and molecules. The largest part of this thesis deals with experiments where molecules are the harmonic generation medium and the re-colliding electron wave packet acts as a 'self-probe'. In several experiments, we demonstrate the potential of this scheme to observe or image ultra-fast intra-molecular electronic and nuclear dynamics. In particular, we have performed the first phase measurements of the high harmonic emission from aligned molecules and we have extracted the recombination dipole matrix element. This observable contains signatures of quantum interference between the continuum and bound parts of the total electronic wavefunction. It is shown how this quantum interference can be utilized to shape the atto-second light emission from the molecules. In a second part of this thesis, we use the well characterized coherent X-UV light emitted by rare gas atoms to photo-ionize molecules. Measuring the ejected photoelectron wave packet then allows to extract information on the photoionization process itself, and possibly about the initial bound and final continuum states of the electron. The last chapter of this manuscript describes studies of high harmonic and atto-second light pulse generation in a different medium: ablation plasmas. (author)

  11. Practical issues of retrieving isolated attosecond pulses

    International Nuclear Information System (INIS)

    Wang He; Chini, Michael; Khan, Sabih D; Chen, Shouyuan; Gilbertson, Steve; Feng Ximao; Mashiko, Hiroki; Chang Zenghu

    2009-01-01

    The attosecond streaking technique is used for the characterization of isolated extreme ultraviolet (XUV) attosecond pulses. This type of measurement suffers from low photoelectron counts in the streaked spectrogram, and is thus susceptible to shot noise. For the retrieval of few- or mono-cycle attosecond pulses, high-intensity streaking laser fields are required, which cause the energy spectrum of above-threshold ionized (ATI) electrons to overlap with that of the streaked photoelectrons. It is found by using the principal component generalized projections algorithm that the XUV attosecond pulse can accurately be retrieved for simulated and experimental spectrograms with a peak value of 50 or more photoelectron counts. Also, the minimum streaking intensity is found to be more than 50 times smaller than that required by the classical streaking camera for retrieval of pulses with a spectral bandwidth supporting 90 as transform-limited pulse durations. Furthermore, spatial variation of the streaking laser intensity, collection angle of streaked electrons and time delay jitter between the XUV pulse and streaking field can degrade the quality of the streaked spectrogram. We find that even when the XUV and streaking laser focal spots are comparable in size, the streaking electrons are collected from a 4π solid angle, or the delay fluctuates by more than the attosecond pulse duration, the attosecond pulses can still be accurately retrieved. In order to explain the insusceptibility of the streaked spectrogram to these factors, the linearity of the streaked spectrogram with respect to the streaking field is derived under the saddle point approximation.

  12. Monitoring conical intersections in the ring opening of furan by attosecond stimulated X-ray Raman spectroscopy

    Directory of Open Access Journals (Sweden)

    Weijie Hua

    2016-03-01

    Full Text Available Attosecond X-ray pulses are short enough to capture snapshots of molecules undergoing nonadiabatic electron and nuclear dynamics at conical intersections (CoIns. We show that a stimulated Raman probe induced by a combination of an attosecond and a femtosecond pulse has a unique temporal and spectral resolution for probing the nonadiabatic dynamics and detecting the ultrafast (∼4.5 fs passage through a CoIn. This is demonstrated by a multiconfigurational self-consistent-field study of the dynamics and spectroscopy of the furan ring-opening reaction. Trajectories generated by surface hopping simulations were used to predict Attosecond Stimulated X-ray Raman Spectroscopy signals at reactant and product structures as well as representative snapshots along the conical intersection seam. The signals are highly sensitive to the changes in nonadiabatically coupled electronic structure and geometry.

  13. Interlayer electron-hole pair multiplication by hot carriers in atomic layer semiconductor heterostructures

    Science.gov (United States)

    Barati, Fatemeh; Grossnickle, Max; Su, Shanshan; Lake, Roger; Aji, Vivek; Gabor, Nathaniel

    Two-dimensional heterostructures composed of atomically thin transition metal dichalcogenides provide the opportunity to design novel devices for the study of electron-hole pair multiplication. We report on highly efficient multiplication of interlayer electron-hole pairs at the interface of a tungsten diselenide / molybdenum diselenide heterostructure. Electronic transport measurements of the interlayer current-voltage characteristics indicate that layer-indirect electron-hole pairs are generated by hot electron impact excitation. Our findings, which demonstrate an efficient energy relaxation pathway that competes with electron thermalization losses, make 2D semiconductor heterostructures viable for a new class of hot-carrier energy harvesting devices that exploit layer-indirect electron-hole excitations. SHINES, an Energy Frontier Research Center funded by the U.S. Department of Energy, Air Force Office of Scientific Research.

  14. Relation between bulk compressibility and surface energy of electron-hole liquids

    International Nuclear Information System (INIS)

    Singwi, K.S.; Tosi, M.P.

    1979-08-01

    Attention is drawn to the existence of an empirical relation chiσ/asup(*)sub(B) approximately 1 between the compressibility, the surface energy and the excitonic radius in electron-hole liquids. (author)

  15. Few-cycle isolated attosecond pulses

    International Nuclear Information System (INIS)

    Sansone, G.; Benedetti, E.; Calegari, F.; Stagira, S.; Vozzi, C.; Silvestri De, S.; Nisoli, M.

    2006-01-01

    Complete test of publication follows. In the last few years the field of attosecond science has shown impressive and rapid progress, mainly due to the introduction of novel experimental methods for the characterization of extreme ultraviolet (XUV) pulses and attosecond electron wave packets. This development has been also triggered by significant improvements in the control of the electric field of the driving infrared pulses. Particularly interesting for the applications is the generation of isolated attosecond XUV pulses using few-cycle driving pulses. In this case significant progresses have been achieved thanks to the stabilization of the carrier-envelope phase (CEP) of amplified light pulses. In this work we demonstrate that the polarization gating (PG) method with few-cycle phase-stabilized driving pulses allows one to generate few-cycle isolated attosecond pulses tunable on a very broad spectral region. The PG method is based on temporal modulation of the ellipticity of a light pulse, which confines the XUV emission in the temporal gate where the polarization is close to linear. The time-dependent polarization of phase-stabilized sub-6-fs pulses, generated by the hollow fiber technique, has been obtained using two birefringent plates. It is possible to create a linear polarization gate, whose position is imposed by the intensity profile of the pulse whilst the emission time is linked to the CEP of the electric field. The pulses have been analyzed by using a flat-field spectrometer. Continuous XUV spectra, corresponding to the production of isolated attosecond pulses, have been generated for particular CEP values. Upon changing the rotation of the first plate it was possible to tune the XUV emission in a broad spectra range. We have then achieved a complete temporal characterization of the generated isolated attosecond pulses using frequency-resolved optical gating for complete reconstruction of attosecond bursts (FROG CRAB). The measured parabolic phase

  16. Macroscopic effects in attosecond pulse generation

    International Nuclear Information System (INIS)

    Ruchon, T; Varju, K; Mansten, E; Swoboda, M; L'Huillier, A; Hauri, C P; Lopez-Martens, R

    2008-01-01

    We examine how the generation and propagation of high-order harmonics in a partly ionized gas medium affect their strength and synchronization. The temporal properties of the resulting attosecond pulses generated in long gas targets can be significantly influenced by macroscopic effects, in particular by the intensity in the medium and the degree of ionization which control the dispersion. Under some conditions, the use of gas targets longer than the absorption length can lead to the generation of compressed attosecond pulses. We show these macroscopic effects experimentally, using a 6 mm-long argon-filled gas cell as the generating medium

  17. Macroscopic effects in attosecond pulse generation

    Energy Technology Data Exchange (ETDEWEB)

    Ruchon, T; Varju, K; Mansten, E; Swoboda, M; L' Huillier, A [Department of Physics, Lund University, PO Box 118, SE-221 00 Lund (Sweden); Hauri, C P; Lopez-Martens, R [Laboratoire d' Optique Appliquee, Ecole Nationale Superieure des Techniques Avancees (ENSTA)-Ecole Polytechnique CNRS UMR 7639, 91761 Palaiseau (France)], E-mail: anne.lhuillier@fysik.lth.se

    2008-02-15

    We examine how the generation and propagation of high-order harmonics in a partly ionized gas medium affect their strength and synchronization. The temporal properties of the resulting attosecond pulses generated in long gas targets can be significantly influenced by macroscopic effects, in particular by the intensity in the medium and the degree of ionization which control the dispersion. Under some conditions, the use of gas targets longer than the absorption length can lead to the generation of compressed attosecond pulses. We show these macroscopic effects experimentally, using a 6 mm-long argon-filled gas cell as the generating medium.

  18. Isolated elliptically polarized attosecond soft X-ray with high-brilliance using polarization gating of harmonics from relativistic plasmas at oblique incidence.

    Science.gov (United States)

    Chen, Zi-Yu; Li, Xiao-Ya; Li, Bo-Yuan; Chen, Min; Liu, Feng

    2018-02-19

    The production of intense isolated attosecond pulse is a major goal in ultrafast research. Recent advances in high harmonic generation from relativistic plasma mirrors under oblique incidence interactions gave rise to photon-rich attosecond pulses with circular or elliptical polarization. However, to achieve an isolated elliptical attosecond pulse via polarization gating using currently available long driving pulses remains a challenge, because polarization gating of high harmonics from relativistic plasmas is assumed only possible at normal or near-normal incidence. Here we numerically demonstrate a scheme around this problem. We show that via control of plasma dynamics by managing laser polarization, it is possible to gate an intense single attosecond pulse with high ellipticity extending to the soft X-ray regime at oblique incidence. This approach thus paves the way towards a powerful tool enabling high-time-resolution probe of dynamics of chiral systems and magnetic materials with current laser technology.

  19. Atomic and molecular phases through attosecond streaking

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Madsen, Lars Bojer

    2011-01-01

    phase of the atomic or molecular ionization matrix elements from the two states through the interference from the two channels. The interference may change the phase of the photoelectron streaking signal within the envelope of the infrared field, an effect to be accounted for when reconstructing short...... pulses from the photoelectron signal and in attosecond time-resolved measurements....

  20. Generation and Characterization of Attosecond Pulses. Final report

    International Nuclear Information System (INIS)

    Ian A. Walmsley; Robert W. Boyd

    2006-01-01

    The research undertaken in this project has been directed toward the area of attoscience, in particular the problem of attosecond metrology. That is, the accurate determination of the electric field of attosecond XUV radiation. This outstanding problem has been identified as a critical technology for further development of the field, and our research adds to the area by providing the first method for characterization using the harmonic radiation itself as a tool. The technical effectiveness of this approach is very high, since it is vastly easier to detect XUV radiation directly than via the spectrum of photoelectrons liberated from atoms by it. This means that the experimental data rate can be much higher in principle using all-optical detection that electron detection, which will greatly aid the utility of harmonic XUV sources in attoscience applications. There are as yet no direct public benefits from this area of scientific research, though access to material structural dynamics on unprecedented brief timescales are expected to yield significant benefits for the future

  1. Modulating the Electron-Hole Interaction in a Hybrid Lead Halide Perovskite with an Electric Field.

    Science.gov (United States)

    Leijtens, Tomas; Srimath Kandada, Ajay Ram; Eperon, Giles E; Grancini, Giulia; D'Innocenzo, Valerio; Ball, James M; Stranks, Samuel D; Snaith, Henry J; Petrozza, Annamaria

    2015-12-16

    Despite rapid developments in both photovoltaic and light-emitting device performance, the understanding of the optoelectronic properties of hybrid lead halide perovskites is still incomplete. In particular, the polarizability of the material, the presence of molecular dipoles, and their influence on the dynamics of the photoexcitations remain an open issue to be clarified. Here, we investigate the effect of an applied external electric field on the photoexcited species of CH3NH3PbI3 thin films, both at room temperature and at low temperature, by monitoring the photoluminescence (PL) yield and PL decays. At room temperature we find evidence for electric-field-induced reduction of radiative bimolecular carrier recombination together with motion of charged defects that affects the nonradiative decay rate of the photoexcited species. At low temperature (190 K), we observe a field-induced enhancement of radiative free carrier recombination rates that lasts even after the removal of the field. We assign this to field-induced alignment of the molecular dipoles, which reduces the vibrational freedom of the lattice and the associated local screening and hence results in a stronger electron-hole interaction.

  2. Plasma phase transition in dense hydrogen and electron-hole plasmas

    CERN Document Server

    Filinov, V S; Levashov, P R; Fortov, V E; Ebeling, W; Schlanges, M; Koch, S W

    2003-01-01

    Plasma phase transitions in dense hydrogen and electron-hole plasmas are investigated by direct path integral Monte Carlo methods. The phase boundary of the electron-hole liquid in germanium is calculated and is found to agree reasonably well with the known experimental results. Analogous behaviour is found for high-density hydrogen. For a temperature of T = 10 000 K it is shown that the internal energy is lowered due to droplet formation for densities between 10 sup 2 sup 3 cm sup - sup 3 and 10 sup 2 sup 4 cm sup - sup 3.

  3. Crossover between the dense electron-hole phase and the BCS excitonic phase in quantum dots

    International Nuclear Information System (INIS)

    Rodriguez, B.A.; Gonzalez, A.; Quiroga, L.; Capote, R.; Rodriguez, F.J.

    1999-09-01

    Second order perturbation theory and a Lipkin-Nogami scheme combined with an exact Monte Carlo projection after variation are applied to compute the ground-state energy of 6 ≤ N ≤ 210 electron-hole pairs confined in a parabolic two-dimensional quantum dot. The energy shows nice scaling properties as N or the confinement strength is varied. A crossover from the high-density electron-hole phase to the BCS excitonic phase is found at a density which is roughly four times the close-packing density of excitons. (author)

  4. Electron-hole pair effects in methane dissociative chemisorption on Ni(111)

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Xuan; Jiang, Bin, E-mail: bjiangch@ustc.edu.cn [Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Juaristi, J. Iñaki [Centro de Física de Materiales CFM/MPC(CSIC-UPV/EHU), P. Manuel de Lardizabal 5, 20018 San Sebastián (Spain); Donostia International Physics Center DIPC, P. Manuel de Lardizabal 4, 20018 San Sebastián (Spain); Departamento de Física de Materiales, Facultad de Químicas, Universidad del País Vasco (UPV/EHU), Apartado 1072, 20080 San Sebastián (Spain); Alducin, Maite [Centro de Física de Materiales CFM/MPC(CSIC-UPV/EHU), P. Manuel de Lardizabal 5, 20018 San Sebastián (Spain); Donostia International Physics Center DIPC, P. Manuel de Lardizabal 4, 20018 San Sebastián (Spain); Guo, Hua [Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

    2016-07-28

    The dissociative chemisorption of methane on metal surfaces has attracted much attention in recent years as a prototype of gas-surface reactions in understanding the mode specific and bond selective chemistry. In this work, we systematically investigate the influence of electron-hole pair excitations on the dissociative chemisorption of CH{sub 4}/CH{sub 3}D/CHD{sub 3} on Ni(111). The energy dissipation induced by surface electron-hole pair excitations is modeled as a friction force introduced in the generalized Langevin equation, in which the independent atomic friction coefficients are determined within the local-density friction approximation. Quasi-classical trajectory calculations for CH{sub 4}/CH{sub 3}D/CHD{sub 3} have been carried out on a recently developed twelve-dimensional potential energy surface. Comparing the dissociation probabilities obtained with and without friction, our results clearly indicate that the electron-hole pair effects are generally small, both on absolute reactivity of each vibrational state and on the mode specificity and bond selectivity. Given similar observations in both water and methane dissociation processes, we conclude that electron-hole pair excitations would not play an important role as long as the reaction is direct and the interaction time between the molecule and metal electrons is relatively short.

  5. Observation of preformed electron-hole Cooper pairs in highly excited ZnO

    NARCIS (Netherlands)

    Versteegh, M.A.M.; van Lange, A.J.; Stoof, H.T.C.; Dijkhuis, J.I.

    2012-01-01

    Electrons and holes in a semiconductor form hydrogen-atom-like bound states, called excitons. At high electron-hole densities the attractive Coulomb force becomes screened and excitons can no longer exist. Bardeen-Cooper-Schrieffer theory predicts that at such high densities co-operative many-body

  6. Charge migration induced by attosecond pulses in bio-relevant molecules

    International Nuclear Information System (INIS)

    Calegari, Francesca; Castrovilli, Mattea C; Nisoli, Mauro; Trabattoni, Andrea; Palacios, Alicia; Ayuso, David; Martín, Fernando; Greenwood, Jason B; Decleva, Piero

    2016-01-01

    After sudden ionization of a large molecule, the positive charge can migrate throughout the system on a sub-femtosecond time scale, purely guided by electronic coherences. The possibility to actively explore the role of the electron dynamics in the photo-chemistry of bio-relevant molecules is of fundamental interest for understanding, and perhaps ultimately controlling, the processes leading to damage, mutation and, more generally, to the alteration of the biological functions of the macromolecule. Attosecond laser sources can provide the extreme time resolution required to follow this ultrafast charge flow. In this review we will present recent advances in attosecond molecular science: after a brief description of the results obtained for small molecules, recent experimental and theoretical findings on charge migration in bio-relevant molecules will be discussed. (topical review)

  7. Far infrared spectroscopy of solids. I. Impurity states in Al2O3. II. Electron-hole droplets in Ge

    International Nuclear Information System (INIS)

    Aurbauch, R.L.

    1975-01-01

    Far infrared Fourier transform spectroscopy was used to study the low lying vibronic states of Mn 3+ in Al 2 O 3 and the plasma absorption of electron-hole droplets in Ge. The transmission of Mn-doped samples of Al 2 O 3 was measured in the frequency range from 3 to 30 cm -1 in applied magnetic fields up to 50 kG. Absorption lines were observed due to both ground and excited state transitions. Polarization measurements established that these absorption lines were due to electric dipole transitions. Temperature dependence measurements were used to derive a level diagram for the low lying states of Mn 3+ . A phenomenological model based on an electronic Hamiltonian was developed which successfully describes the data. The empirically determined trigonal field and spin-orbit quenching parameters of this model are 0.7 and 0.1 respectively. This quenching is attributed to the dynamic Jahn--Teller interaction. The plasma absorption of small (α) electron-hole drops in Ge was measured in the frequency range from 30 to 300 cm -1 . The observed absorption is in good agreement with measurements by Vavilov and other workers. A theoretical model which includes both intraband and interband contributions to the dielectric constant in the Rayleigh limit of Mie theory is used to describe the observed lineshape. Measurements of plasma absorption of large (γ) drops in inhomogeneously stressed Ge were made in magnetic fields up to 50 kG. The lineshape at zero applied field was calculated in the large sphere limit of Mie theory including intraband terms and a zero-strain interband term. Qualitative agreement with experiment was obtained. The peak absorption shifted quadratically with applied magnetic field and the total plasma absorption increased. No oscillatory structure was observed in the field-dependence of the total absorption

  8. Frequency chirp of harmonic and attosecond pulses

    International Nuclear Information System (INIS)

    Varju, K.; Johansson, P; L'Huillier, A.L.; Mairesse, Y.; Salieres, P.

    2005-01-01

    Full text: We have explored in detail the first- and second-order variations of the atomic phase as a function of the laser intensity and harmonic order. This unravels the similitudes and differences existing between the chirp of individual harmonic pulses and the chirp of the attosecond pulses. We show that the two techniques XFROG and RABITT used to characterize the two chirps (respectively) converge to give the same information, namely the values of the mixed partial derivatives of the atomic phase. This underlines the common physical origin of all these phenomena and provides a unified frame for their description and understanding. Ref. 1 (author)

  9. Control of the launch of attosecond pulses

    International Nuclear Information System (INIS)

    Cao Wei; Lu Peixiang; Lan Pengfei; Wang Xinlin; Li Yuhua

    2007-01-01

    We propose an approach to steer the launch of attosecond (as) pulses with a high precision. We numerically demonstrate that by adding a weak second-harmonic (SH) field to the fundamental beam the ionization and recollision process of the electron will be perturbed, which can induce a variation of the emission time of high harmonics. Through modifying the relative intensity of the SH and fundamental fields, the launch of as pulses can be manipulated with a resolution less than 40 as. This will show significant potential for ultrafast optics

  10. Attosecond electron pulse trains and quantum state reconstruction in ultrafast transmission electron microscopy

    Science.gov (United States)

    Priebe, Katharina E.; Rathje, Christopher; Yalunin, Sergey V.; Hohage, Thorsten; Feist, Armin; Schäfer, Sascha; Ropers, Claus

    2017-12-01

    Ultrafast electron and X-ray imaging and spectroscopy are the basis for an ongoing revolution in the understanding of dynamical atomic-scale processes in matter. The underlying technology relies heavily on laser science for the generation and characterization of ever shorter pulses. Recent findings suggest that ultrafast electron microscopy with attosecond-structured wavefunctions may be feasible. However, such future technologies call for means to both prepare and fully analyse the corresponding free-electron quantum states. Here, we introduce a framework for the preparation, coherent manipulation and characterization of free-electron quantum states, experimentally demonstrating attosecond electron pulse trains. Phase-locked optical fields coherently control the electron wavefunction along the beam direction. We establish a new variant of quantum state tomography—`SQUIRRELS'—for free-electron ensembles. The ability to tailor and quantitatively map electron quantum states will promote the nanoscale study of electron-matter entanglement and new forms of ultrafast electron microscopy down to the attosecond regime.

  11. Towards attosecond X-ray pulses from the FEL

    International Nuclear Information System (INIS)

    Zholents, Alexander A.; Fawley, William M.

    2004-01-01

    The ability to study ultrafast phenomena has been recently advanced by the demonstrated production and measurement of a single, 650-attosecond (10 18 sec), VUV x-ray pulse[1] and, latter, a 250-attosecond pulse[2]. The next frontier is a production of the x-ray pulses with shorter wavelengths and in a broader spectral range. Several techniques for a generation of an isolated, attosecond duration, short-wavelength x-ray pulse based upon the ponderomotive laser acceleration [3], SASE and harmonic cascade FELs ([4] - [6]) had been already proposed. In this paper we briefly review a technique proposed in [5] and present some new results

  12. Reconstruction of Attosecond Pulse Trains Using an Adiabatic Phase Expansion

    International Nuclear Information System (INIS)

    Varju, K.; Gustafsson, E.; Johnsson, P.; Mauritsson, J.; L'Huillier, A.; Mairesse, Y.; Agostini, P.; Breger, P.; Carre, B.; Merdji, H.; Monchicourt, P.; Salieres, P.; Frasinski, L.J.

    2005-01-01

    We propose a new method to reconstruct the electric field of attosecond pulse trains. The phase of the high-order harmonic emission electric field is Taylor expanded around the maximum of the laser pulse envelope in the time domain and around the central harmonic in the frequency domain. Experimental measurements allow us to determine the coefficients of this expansion and to characterize the radiation with attosecond accuracy over a femtosecond time scale. The method gives access to pulse-to-pulse variations along the train, including the timing, the chirp, and the attosecond carrier envelope phase

  13. Electrostatics of electron-hole interactions in van der Waals heterostructures

    Science.gov (United States)

    Cavalcante, L. S. R.; Chaves, A.; Van Duppen, B.; Peeters, F. M.; Reichman, D. R.

    2018-03-01

    The role of dielectric screening of electron-hole interaction in van der Waals heterostructures is theoretically investigated. A comparison between models available in the literature for describing these interactions is made and the limitations of these approaches are discussed. A simple numerical solution of Poisson's equation for a stack of dielectric slabs based on a transfer matrix method is developed, enabling the calculation of the electron-hole interaction potential at very low computational cost and with reasonable accuracy. Using different potential models, direct and indirect exciton binding energies in these systems are calculated within Wannier-Mott theory, and a comparison of theoretical results with recent experiments on excitons in two-dimensional materials is discussed.

  14. Coulomb drag in electron-hole bilayer: Mass-asymmetry and exchange correlation effects

    Science.gov (United States)

    Arora, Priya; Singh, Gurvinder; Moudgil, R. K.

    2018-04-01

    Motivated by a recent experiment by Zheng et al. [App. Phys. Lett. 108, 062102 (2016)] on coulomb drag in electron-hole and hole-hole bilayers based on GaAs/AlGaAs semiconductor heterostructure, we investigate theoretically the influence of mass-asymmetry and temperature-dependence of correlations on the drag rate. The correlation effects are dealt with using the Vignale-Singwi effective inter-layer interaction model which includes correlations through local-field corrections to the bare coulomb interactions. However, in this work, we have incorporated only the intra-layer correlations using the temperature-dependent Hubbard approximation. Our results display a reasonably good agreement with the experimental data. However, it is crucial to include both the electron-hole mass-asymmetry and temperature-dependence of correlations. Mass-asymmetry and correlations are found to result in a substantial enhancement of drag resistivity.

  15. High-temperature electron-hole superfluidity with strong anisotropic gaps in double phosphorene monolayers

    Science.gov (United States)

    Saberi-Pouya, S.; Zarenia, M.; Perali, A.; Vazifehshenas, T.; Peeters, F. M.

    2018-05-01

    Excitonic superfluidity in double phosphorene monolayers is investigated using the BCS mean-field equations. Highly anisotropic superfluidity is predicted where we found that the maximum superfluid gap is in the Bose-Einstein condensate (BEC) regime along the armchair direction and in the BCS-BEC crossover regime along the zigzag direction. We estimate the highest Kosterlitz-Thouless transition temperature with maximum value up to ˜90 K with onset carrier densities as high as 4 ×1012cm-2 . This transition temperature is significantly larger than what is found in double electron-hole few-layers graphene. Our results can guide experimental research toward the realization of anisotropic condensate states in electron-hole phosphorene monolayers.

  16. Attosecond delay in the molecular photoionization of asymmetric molecules.

    Science.gov (United States)

    Chacón, Alexis; Ruiz, Camilo

    2018-02-19

    We report theoretical calculations of the delay in photoemission from CO with particular emphasis on the role of the ultrafast electronic bound dynamics. We study the delays in photoionization in the HOMO and HOMO-1 orbitals of the CO molecule by looking into the stereo Wigner time delay technique. That compares the delay in photoemission from electrons emitted to the left and right to extract structural and dynamical information of the ionization process. For this we apply two techniques: The attosecond streak camera and the time of flight technique. Although they should provide the same results we have found large discrepancies of up to 36 in the case of HOMO, while for the HOMO-1 we obtain the same results with the two techniques. We have found that the large time delays observed in the HOMO orbital with the streaking technique are a consequence of the resonant transition triggered by the streaking field. This resonant transition produces a bound electron wavepacket that modifies the measurements of delay in photoionization. As a result of this observation, our technique allows us to reconstruct the bound wavepacket dynamics induced by the streaking field. By measuring the expected value of the electron momentum along the polarization direction after the streaking field has finished, we can recover the relative phase between the complex amplitudes of the HOMO and LUMO orbitals. These theoretical calculations pave the way for the measurement of ultrafast bound-bound electron transitionsand its crucial role for the delay in photoemission observation.

  17. Stability of Sarma phases in density imbalanced electron-hole bilayer systems

    International Nuclear Information System (INIS)

    Subasi, A. L.; Tanatar, B.; Pieri, P.; Senatore, G.

    2010-01-01

    We study excitonic condensation in an electron-hole bilayer system with unequal layer densities at zero temperature. Using mean-field theory we solve the Bardeen-Cooper-Schrieffer (BCS) gap equations numerically and investigate the effects of intralayer interactions. The electron-hole system evolves from BCS in the weak coupling limit to Bose-Einstein condensation (BEC) in the strong coupling limit. We analyze the stability of the Sarma phase with k,-k pairing by calculating the superfluid mass density and also by checking the compressibility matrix. We find that with bare Coulomb interactions the superfluid density is always positive in the Sarma phase, due to a peculiar momentum structure of the gap function originating from the singular behavior of the Coulomb potential at zero momentum and the presence of a sharp Fermi surface. Introducing a simple model for screening, we find that the superfluid density becomes negative in some regions of the phase diagram, corresponding to an instability toward a Fulde-Ferrel-Larkin-Ovchinnikov-type superfluid phase. Thus, intralayer interaction and screening together can lead to a rich phase diagram in the BCS-BEC crossover regime in electron-hole bilayer systems.

  18. The effects of electron-hole separation on the photoconductivity of individual metal oxide nanowires

    International Nuclear Information System (INIS)

    Prades, J D; Hernandez-Ramirez, F; Jimenez-Diaz, R; Manzanares, M; Andreu, T; Cirera, A; Romano-Rodriguez, A; Morante, J R

    2008-01-01

    The responses of individual ZnO nanowires to UV light demonstrate that the persistent photoconductivity (PPC) state is directly related to the electron-hole separation near the surface. Our results demonstrate that the electrical transport in these nanomaterials is influenced by the surface in two different ways. On the one hand, the effective mobility and the density of free carriers are determined by recombination mechanisms assisted by the oxidizing molecules in air. This phenomenon can also be blocked by surface passivation. On the other hand, the surface built-in potential separates the photogenerated electron-hole pairs and accumulates holes at the surface. After illumination, the charge separation makes the electron-hole recombination difficult and originates PPC. This effect is quickly reverted after increasing either the probing current (self-heating by Joule dissipation) or the oxygen content in air (favouring the surface recombination mechanisms). The model for PPC in individual nanowires presented here illustrates the intrinsic potential of metal oxide nanowires to develop optoelectronic devices or optochemical sensors with better and new performances.

  19. Coherent electron - hole state and femtosecond cooperative emission in bulk GaAs

    International Nuclear Information System (INIS)

    Vasil'ev, Petr P; Kan, H; Ohta, H; Hiruma, T

    2002-01-01

    The conditions for obtaining a collective coherent electron - hole state in semiconductors are discussed. The results of the experimental study of the regime of cooperative recombination of high-density electrons and holes (more than 3 x 10 18 cm -3 ) in bulk GaAs at room temperature are presented. It is shown that the collective pairing of electrons and holes and their condensation cause the formation of a short-living coherent electron - hole BCS-like state, which exhibits radiative recombination in the form of high-power femtosecond optical pulses. It is experimentally demonstrated that almost all of the electrons and holes available are condensed at the very bottoms of the bands and are at the cooperative state. The average lifetime of this state is measured to be of about 300 fs. The dependences of the order parameter (the energy gap of the spectrum of electrons and holes) and the Fermi energy of the coherent BCS state on the electron - hole concentration are obtained. (special issue devoted to the 80th anniversary of academician n g basov's birth)

  20. Electron holes in phase space: What they are and why they matter

    Science.gov (United States)

    Hutchinson, I. H.

    2017-05-01

    This is a tutorial and selective review explaining the fundamental concepts and some currently open questions concerning the plasma phenomenon of the electron hole. The widespread occurrence of electron holes in numerical simulations, space-craft observations, and laboratory experiments is illustrated. The elementary underlying theory is developed of a one-dimensional electron hole as a localized potential maximum, self-consistently sustained by a deficit of trapped electron phase-space density. The spatial extent of a hole is typically a few Debye lengths; what determines the minimum and maximum possible lengths is explained, addressing the key aspects of the as yet unsettled dispute between the integral and differential approaches to hole structure. In multiple dimensions, holes tend to form less readily; they generally require a magnetic field and distribution-function anisotropy. The mechanisms by which they break up are explained, noting that this transverse instability is not fully understood. Examples are given of plasma circumstances where holes play an important role, and of recent progress on understanding their holistic kinematics and self-acceleration.

  1. Interaction of non-equilibrium phonons with electron-hole plasmas in germanium

    International Nuclear Information System (INIS)

    Kirch, S.J.

    1985-01-01

    This thesis presents results of experiments on the interaction of phonons and photo-excited electron-hole plasmas in Ge at low temperature. The first two studies involved the low-temperature fluid phase known as the electron-hole liquid (EHL). The third study involved a wider range of temperatures and includes the higher temperature electron-hole plasma (EHP). In the first experiment, superconducting tunnel junctions are used to produce quasi-monochromatic phonons, which propagate through the EHL. The magnitude of the absorption of these non-equilibrium phonons gives a direct measure of the coupling constant, the deformation potential. In the second experiment, the nonequilibrium phonons are generated by laser excitation of a metal film. An unusual sample geometry allows examination of the EHL-phonon interaction near the EHL excitation surface. This coupling is examined for both cw and pulsed EHL excitation. In the third experiment, the phonons are byproducts of the photo-excited carrier thermalization. The spatial, spectral and temporal dependence of the recombination luminescence is examined. A phonon wind force is observed to dominate the transport properties of the EHL and the EHP. These carriers are never observed to move faster than the phonon velocity even during the laser pulse

  2. Fermi-edge superfluorescence from a quantum-degenerate electron-hole gas

    Science.gov (United States)

    Kim, Ji-Hee; , G. Timothy Noe, II; McGill, Stephen A.; Wang, Yongrui; Wójcik, Aleksander K.; Belyanin, Alexey A.; Kono, Junichiro

    2013-11-01

    Nonequilibrium can be a source of order. This rather counterintuitive statement has been proven to be true through a variety of fluctuation-driven, self-organization behaviors exhibited by out-of-equilibrium, many-body systems in nature (physical, chemical, and biological), resulting in the spontaneous appearance of macroscopic coherence. Here, we report on the observation of spontaneous bursts of coherent radiation from a quantum-degenerate gas of nonequilibrium electron-hole pairs in semiconductor quantum wells. Unlike typical spontaneous emission from semiconductors, which occurs at the band edge, the observed emission occurs at the quasi-Fermi edge of the carrier distribution. As the carriers are consumed by recombination, the quasi-Fermi energy goes down toward the band edge, and we observe a continuously red-shifting streak. We interpret this emission as cooperative spontaneous recombination of electron-hole pairs, or superfluorescence (SF), which is enhanced by Coulomb interactions near the Fermi edge. This novel many-body enhancement allows the magnitude of the spontaneously developed macroscopic polarization to exceed the maximum value for ordinary SF, making electron-hole SF even more ``super'' than atomic SF.

  3. Linked-cluster formulation of electron-hole interaction kernel in real-space representation without using unoccupied states.

    Science.gov (United States)

    Bayne, Michael G; Scher, Jeremy A; Ellis, Benjamin H; Chakraborty, Arindam

    2018-05-21

    Electron-hole or quasiparticle representation plays a central role in describing electronic excitations in many-electron systems. For charge-neutral excitation, the electron-hole interaction kernel is the quantity of interest for calculating important excitation properties such as optical gap, optical spectra, electron-hole recombination and electron-hole binding energies. The electron-hole interaction kernel can be formally derived from the density-density correlation function using both Green's function and TDDFT formalism. The accurate determination of the electron-hole interaction kernel remains a significant challenge for precise calculations of optical properties in the GW+BSE formalism. From the TDDFT perspective, the electron-hole interaction kernel has been viewed as a path to systematic development of frequency-dependent exchange-correlation functionals. Traditional approaches, such as MBPT formalism, use unoccupied states (which are defined with respect to Fermi vacuum) to construct the electron-hole interaction kernel. However, the inclusion of unoccupied states has long been recognized as the leading computational bottleneck that limits the application of this approach for larger finite systems. In this work, an alternative derivation that avoids using unoccupied states to construct the electron-hole interaction kernel is presented. The central idea of this approach is to use explicitly correlated geminal functions for treating electron-electron correlation for both ground and excited state wave functions. Using this ansatz, it is derived using both diagrammatic and algebraic techniques that the electron-hole interaction kernel can be expressed only in terms of linked closed-loop diagrams. It is proved that the cancellation of unlinked diagrams is a consequence of linked-cluster theorem in real-space representation. The electron-hole interaction kernel derived in this work was used to calculate excitation energies in many-electron systems and results

  4. Photoelectron spectrometer for attosecond spectroscopy of liquids and gases

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, I.; Huppert, M.; Wörner, H. J., E-mail: hwoerner@ethz.ch [Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich (Switzerland); Brown, M. A. [Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 5, 8093 Zurich (Switzerland); Bokhoven, J. A. van [Institute for Chemical and Bioengineering, ETH Zurich, Vladimir-Prelog-Weg 1, 8093 Zurich (Switzerland); Laboratory for Catalysis and Sustainable Chemistry, Paul Scherrer Institute, 5232 Villigen (Switzerland)

    2015-12-15

    A new apparatus for attosecond time-resolved photoelectron spectroscopy of liquids and gases is described. It combines a liquid microjet source with a magnetic-bottle photoelectron spectrometer and an actively stabilized attosecond beamline. The photoelectron spectrometer permits venting and pumping of the interaction chamber without affecting the low pressure in the flight tube. This pressure separation has been realized through a sliding skimmer plate, which effectively seals the flight tube in its closed position and functions as a differential pumping stage in its open position. A high-harmonic photon spectrometer, attached to the photoelectron spectrometer, exit port is used to acquire photon spectra for calibration purposes. Attosecond pulse trains have been used to record photoelectron spectra of noble gases, water in the gas and liquid states as well as solvated species. RABBIT scans demonstrate the attosecond resolution of this setup.

  5. Photoelectron spectrometer for attosecond spectroscopy of liquids and gases

    International Nuclear Information System (INIS)

    Jordan, I.; Huppert, M.; Wörner, H. J.; Brown, M. A.; Bokhoven, J. A. van

    2015-01-01

    A new apparatus for attosecond time-resolved photoelectron spectroscopy of liquids and gases is described. It combines a liquid microjet source with a magnetic-bottle photoelectron spectrometer and an actively stabilized attosecond beamline. The photoelectron spectrometer permits venting and pumping of the interaction chamber without affecting the low pressure in the flight tube. This pressure separation has been realized through a sliding skimmer plate, which effectively seals the flight tube in its closed position and functions as a differential pumping stage in its open position. A high-harmonic photon spectrometer, attached to the photoelectron spectrometer, exit port is used to acquire photon spectra for calibration purposes. Attosecond pulse trains have been used to record photoelectron spectra of noble gases, water in the gas and liquid states as well as solvated species. RABBIT scans demonstrate the attosecond resolution of this setup

  6. Photoelectron spectrometer for attosecond spectroscopy of liquids and gases

    Science.gov (United States)

    Jordan, I.; Huppert, M.; Brown, M. A.; van Bokhoven, J. A.; Wörner, H. J.

    2015-12-01

    A new apparatus for attosecond time-resolved photoelectron spectroscopy of liquids and gases is described. It combines a liquid microjet source with a magnetic-bottle photoelectron spectrometer and an actively stabilized attosecond beamline. The photoelectron spectrometer permits venting and pumping of the interaction chamber without affecting the low pressure in the flight tube. This pressure separation has been realized through a sliding skimmer plate, which effectively seals the flight tube in its closed position and functions as a differential pumping stage in its open position. A high-harmonic photon spectrometer, attached to the photoelectron spectrometer, exit port is used to acquire photon spectra for calibration purposes. Attosecond pulse trains have been used to record photoelectron spectra of noble gases, water in the gas and liquid states as well as solvated species. RABBIT scans demonstrate the attosecond resolution of this setup.

  7. Lewis Base Passivation of Hybrid Halide Perovskites Slows Electron-Hole Recombination: Time-Domain Ab Initio Analysis.

    Science.gov (United States)

    Liu, Lihong; Fang, Wei-Hai; Long, Run; Prezhdo, Oleg V

    2018-03-01

    Nonradiative electron-hole recombination plays a key role in determining photon conversion efficiencies in solar cells. Experiments demonstrate significant reduction in the recombination rate upon passivation of methylammonium lead iodide perovskite with Lewis base molecules. Using nonadiabatic molecular dynamics combined with time-domain density functional theory, we find that the nonradiative charge recombination is decelerated by an order of magnitude upon adsorption of the molecules. Thiophene acts by the traditional passivation mechanism, forcing electron density away from the surface. In contrast, pyridine localizes the electron at the surface while leaving it energetically near the conduction band edge. This is because pyridine creates a stronger coordinative bond with a lead atom of the perovskite and has a lower energy unoccupied orbital compared with thiophene due to the more electronegative nitrogen atom relative to thiophene's sulfur. Both molecules reduce two-fold the nonadiabatic coupling and electronic coherence time. A broad range of vibrational modes couple to the electronic subsystem, arising from inorganic and organic components. The simulations reveal the atomistic mechanisms underlying the enhancement of the excited-state lifetime achieved by the perovskite passivation, rationalize the experimental results, and advance our understanding of charge-phonon dynamics in perovskite solar cells.

  8. Potential beneficial effects of electron-hole plasmas created in silicon sensors by XFEL-like high intensity pulses for detector development

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, Joel T.; Becker, Julian; Shanks, Katherine S.; Philipp, Hugh T.; Tate, Mark W. [Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY 14853 (United States); Gruner, Sol M., E-mail: smg26@cornell.edu [Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY 14853 (United States); Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, NY 14853 (United States)

    2016-07-27

    There is a compelling need for a high frame rate imaging detector with a wide dynamic range, from single x-rays/pixel/pulse to >10{sup 6} x-rays/pixel/pulse, that is capable of operating at both x-ray free electron laser (XFEL) and 3rd generation sources with sustained fluxes of > 10{sup 11} x-rays/pixel/s [1, 2, 3]. We propose to meet these requirements with the High Dynamic Range Pixel Array Detector (HDR-PAD) by (a) increasing the speed of charge removal strategies [4], (b) increasing integrator range by implementing adaptive gain [5], and (c) exploiting the extended charge collection times of electron-hole pair plasma clouds that form when a sufficiently large number of x-rays are absorbed in a detector sensor in a short period of time [6]. We have developed a measurement platform similar to the one used in [6] to study the effects of high electron-hole densities in silicon sensors using optical lasers to emulate the conditions found at XFELs. Characterizations of the employed tunable wavelength laser with picosecond pulse duration have shown Gaussian focal spots sizes of 6 ± 1 µm rms over the relevant spectrum and 2 to 3 orders of magnitude increase in available intensity compared to previous measurements presented in [6]. Results from measurements on a typical pixelated silicon diode intended for use with the HDR-PAD (150 µm pixel size, 500 µm thick sensor) are presented.

  9. Effects of surface motion and electron-hole pair excitations in CO2 dissociation and scattering on Ni(100)

    Science.gov (United States)

    Luo, Xuan; Zhou, Xueyao; Jiang, Bin

    2018-05-01

    The energy transfer between different channels is an important aspect in chemical reactions at surfaces. We investigate here in detail the energy transfer dynamics in a prototypical system, i.e., reactive and nonreactive scattering of CO2 on Ni(100), which is related to heterogeneous catalytic processes with Ni-based catalysts for CO2 reduction. On the basis of our earlier nine-dimensional potential energy surface for CO2/Ni(100), dynamical calculations have been done using the generalized Langevin oscillator (GLO) model combined with local density friction approximation (LDFA), in which the former accounts for the surface motion and the latter accounts for the low-energy electron-hole pair (EHP) excitation. In spite of its simplicity, it is found that the GLO model yields quite satisfactory results, including the significant energy loss and product energy disposal, trapping, and steering dynamics, all of which agree well with the ab initio molecular dynamics ones where many surface atoms are explicitly involved with high computational cost. However, the GLO model fails to describe the reactivity enhancement due to the lattice motion because it intrinsically does not incorporate the variance of barrier height on the surface atom displacement. On the other hand, in LDFA, the energy transferred to EHPs is found to play a minor role and barely alter the dynamics, except for slightly reducing the dissociation probabilities. In addition, vibrational state-selected dissociative sticking probabilities are calculated and previously observed strong mode specificity is confirmed. Our work suggests that further improvement of the GLO model is needed to consider the lattice-induced barrier lowering.

  10. High-throughput beamline for attosecond pulses based on toroidal mirrors with microfocusing capabilities

    Energy Technology Data Exchange (ETDEWEB)

    Frassetto, F.; Poletto, L., E-mail: poletto@dei.unipd.it [National Research Council, Institute of Photonics and Nanotechnologies, via Trasea 7, 35131 Padova (Italy); Trabattoni, A.; Anumula, S.; Sansone, G. [Department of Physics, Politecnico di Milano, Piazza L. Da Vinci 32, 20133 Milano (Italy); Calegari, F. [National Research Council, Institute of Photonics and Nanotechnologies, Piazza L. da Vinci 32, 20133 Milano (Italy); Nisoli, M. [Department of Physics, Politecnico di Milano, Piazza L. Da Vinci 32, 20133 Milano (Italy); National Research Council, Institute of Photonics and Nanotechnologies, Piazza L. da Vinci 32, 20133 Milano (Italy)

    2014-10-15

    We have developed a novel attosecond beamline designed for attosecond-pump/attosecond probe experiments. Microfocusing of the Extreme-ultraviolet (XUV) radiation is obtained by using a coma-compensated optical configuration based on the use of three toroidal mirrors controlled by a genetic algorithm. Trains of attosecond pulses are generated with a measured peak intensity of about 3 × 10{sup 11} W/cm{sup 2}.

  11. High-throughput beamline for attosecond pulses based on toroidal mirrors with microfocusing capabilities

    International Nuclear Information System (INIS)

    Frassetto, F.; Poletto, L.; Trabattoni, A.; Anumula, S.; Sansone, G.; Calegari, F.; Nisoli, M.

    2014-01-01

    We have developed a novel attosecond beamline designed for attosecond-pump/attosecond probe experiments. Microfocusing of the Extreme-ultraviolet (XUV) radiation is obtained by using a coma-compensated optical configuration based on the use of three toroidal mirrors controlled by a genetic algorithm. Trains of attosecond pulses are generated with a measured peak intensity of about 3 × 10 11 W/cm 2

  12. Effects of density imbalance on the BCS-BEC crossover in semiconductor electron-hole bilayers

    International Nuclear Information System (INIS)

    Pieri, P.; Strinati, G. C.; Neilson, D.

    2007-01-01

    We study the occurrence of excitonic superfluidity in electron-hole bilayers at zero temperature. We not only identify the crossover in the phase diagram from the BCS limit of overlapping pairs to the BEC limit of nonoverlapping tightly bound pairs but also, by varying the electron and hole densities independently, we can analyze a number of phases that occur mainly in the crossover region. With different electron and hole effective masses, the phase diagram is asymmetric with respect to excess electron or hole densities. We propose, as the criterion for the onset of superfluidity, the jump of the electron and hole chemical potentials when their densities cross

  13. Electron-Hole Asymmetry of Spin Injection and Transport in Single-Layer Graphene

    OpenAIRE

    Han, Wei; Wang, W. H.; Pi, K.; McCreary, K. M.; Bao, W.; Li, Yan; Miao, F.; Lau, C. N.; Kawakami, R. K.

    2009-01-01

    Spin-dependent properties of single-layer graphene (SLG) have been studied by non-local spin valve measurements at room temperature. Gate voltage dependence shows that the non-local magnetoresistance (MR) is proportional to the conductivity of the SLG, which is the predicted behavior for transparent ferromagnetic/nonmagnetic contacts. While the electron and hole bands in SLG are symmetric, gate voltage and bias dependence of the non-local MR reveal an electron-hole asymmetry in which the non-...

  14. Plasmon sidebands in the gain spectrum of an electron-hole plasma

    International Nuclear Information System (INIS)

    Hoang Ngoc Cam; Nguyen Van Hieu; Nguyen Ai Viet.

    1987-06-01

    The theory is represented for the recombination of the electron-hole pair into the photon with and without the emission of the plasmon-phonon coupled modes. In calculating the energies of the plasmon and the plasmon-phonon coupled modes as well as the vertices of their effective interactions the quantum field theory method has been applied. The theoretical prediction agrees well with the experimental result in the main part EHP 0 and the first sideband EHP - of the gain spectrum. (author). 6 refs, 9 figs

  15. BEC-BCS-laser crossover in Coulomb-correlated electron-hole-photon systems

    International Nuclear Information System (INIS)

    Yamaguchi, M; Kamide, K; Ogawa, T; Yamamoto, Y

    2012-01-01

    Many-body features caused by Coulomb correlations are of great importance for understanding phenomena pertaining to polariton systems in semiconductor microcavities, i.e. electron-hole-photon systems. Remarkable many-body effects are shown to exist in both thermal-equilibrium phases and non-equilibrium lasing states. We then show a unified framework for connecting the thermal-equilibrium and the non-equilibrium steady states based on a non-equilibrium Green's function approach. Bose-Einstein condensate (BEC)-Bardeen-Cooper-Schrieffer (BCS)-laser crossovers are investigated by using this approach. (paper)

  16. Generation of atto-second pulses on relativistic mirror plasma

    International Nuclear Information System (INIS)

    Vincenti, H.

    2012-12-01

    When an ultra intense femtosecond laser (I > 10 16 W.cm -2 ) with high contrast is focused on a solid target, the laser field at focus is high enough to completely ionize the target surface during the rising edge of the laser pulse and form a plasma. This plasma is so dense (the electron density is of the order of hundred times the critical density) that it completely reflects the incident laser beam in the specular direction: this is the so-called 'plasma mirror'. When laser intensity becomes very high, the non-linear response of the plasma mirror to the laser field periodically deforms the incident electric field leading to high harmonic generation in the reflected beam. In the temporal domain this harmonic spectrum is associated to a train of atto-second pulses. The goals of my work were to get a better comprehension of the properties of harmonic beams produced on plasma mirrors and design new methods to control theses properties, notably in order to produce isolated atto-second pulses instead of trains. Initially, we imagined and modeled the first realistic technique to generate isolated atto-second on plasma mirrors. This brand new approach is based on a totally new physical effect: 'the atto-second lighthouse effect'. Its principle consists in sending the atto-second pulses of the train in different directions and selects one of these pulses by putting a slit in the far field. Despite its simplicity, this technique is very general and applies to any high harmonic generation mechanism. Moreover, the atto-second lighthouse effect has many other applications (e.g in metrology). In particular, it paves the way to atto-second pump-probe experiments. Then, we studied the spatial properties of these harmonics, whose control and characterization are crucial if one wants to use this source in future application experiments. For instance, we need to control very precisely the harmonic beam divergence in order to achieve the atto-second lighthouse effect and get

  17. Transport Properties of an Electron-Hole Bilayer in Contact with a Superconductor Hybrid Junction

    Science.gov (United States)

    Bercioux, D.; Klapwijk, T. M.; Bergeret, F. S.

    2017-08-01

    We investigate the transport properties of a junction consisting of an electron-hole bilayer in contact with normal and superconducting leads. The electron-hole bilayer is considered as a semimetal with two electronic bands. We assume that in the region between the contacts the system hosts an exciton condensate described by a BCS-like model with a gap Γ in the quasiparticle density of states. We first discuss how the subgap electronic transport through the junction is mainly governed by the interplay between two kinds of reflection processes at the interfaces: the standard Andreev reflection at the interface between the superconductor and the exciton condensate, and a coherent crossed reflection at the semimetal-exciton-condensate interface that converts electrons from one layer into the other. We show that the differential conductance of the junction shows a minimum at voltages of the order of Γ /e . Such a minimum can be seen as a direct hallmark of the existence of the gapped excitonic state.

  18. Electron-hole collision limited transport in charge-neutral bilayer graphene

    Science.gov (United States)

    Nam, Youngwoo; Ki, Dong-Keun; Soler-Delgado, David; Morpurgo, Alberto F.

    2017-12-01

    Ballistic transport occurs whenever electrons propagate without collisions deflecting their trajectory. It is normally observed in conductors with a negligible concentration of impurities, at low temperature, to avoid electron-phonon scattering. Here, we use suspended bilayer graphene devices to reveal a new regime, in which ballistic transport is not limited by scattering with phonons or impurities, but by electron-hole collisions. The phenomenon manifests itself in a negative four-terminal resistance that becomes visible when the density of holes (electrons) is suppressed by gate-shifting the Fermi level in the conduction (valence) band, above the thermal energy. For smaller densities, transport is diffusive, and the measured conductivity is reproduced quantitatively, with no fitting parameters, by including electron-hole scattering as the only process causing velocity relaxation. Experiments on a trilayer device show that the phenomenon is robust and that transport at charge neutrality is governed by the same physics. Our results provide a textbook illustration of a transport regime that had not been observed previously and clarify the nature of conduction through charge-neutral graphene under conditions in which carrier density inhomogeneity is immaterial. They also demonstrate that transport can be limited by a fully electronic mechanism, originating from the same microscopic processes that govern the physics of Dirac-like plasmas.

  19. Helical edge states and fractional quantum Hall effect in a graphene electron-hole bilayer.

    Science.gov (United States)

    Sanchez-Yamagishi, Javier D; Luo, Jason Y; Young, Andrea F; Hunt, Benjamin M; Watanabe, Kenji; Taniguchi, Takashi; Ashoori, Raymond C; Jarillo-Herrero, Pablo

    2017-02-01

    Helical 1D electronic systems are a promising route towards realizing circuits of topological quantum states that exhibit non-Abelian statistics. Here, we demonstrate a versatile platform to realize 1D systems made by combining quantum Hall (QH) edge states of opposite chiralities in a graphene electron-hole bilayer at moderate magnetic fields. Using this approach, we engineer helical 1D edge conductors where the counterpropagating modes are localized in separate electron and hole layers by a tunable electric field. These helical conductors exhibit strong non-local transport signals and suppressed backscattering due to the opposite spin polarizations of the counterpropagating modes. Unlike other approaches used for realizing helical states, the graphene electron-hole bilayer can be used to build new 1D systems incorporating fractional edge states. Indeed, we are able to tune the bilayer devices into a regime hosting fractional and integer edge states of opposite chiralities, paving the way towards 1D helical conductors with fractional quantum statistics.

  20. Combined UMC- DFT prediction of electron-hole coupling in unit cells of pentacene crystals.

    Science.gov (United States)

    Leal, Luciano Almeida; de Souza Júnior, Rafael Timóteo; de Almeida Fonseca, Antonio Luciano; Ribeiro Junior, Luiz Antonio; Blawid, Stefan; da Silva Filho, Demetrio Antonio; da Cunha, Wiliam Ferreira

    2017-05-01

    Pentacene is an organic semiconductor that draws special attention from the scientific community due to the high mobility of its charge carriers. As electron-hole interactions are important aspects in the regard of such property, a computationally inexpensive method to predict the coupling between these quasi-particles is highly desired. In this work, we propose a hybrid methodology of combining Uncoupled Monte Carlo Simulations (UMC) and Density functional Theory (DFT) methodologies to obtain a good compromise between computational feasibility and accuracy. As a first step in considering a Pentacene crystal, we describe its unit cell: the Pentacene Dimer. Because many conformations can be encountered for the dimer and considering the complexity of the system, we make use of UMC in order to find the most probable structures and relative orientations for the Pentacene-Pentacene complex. Following, we carry out electronic structure calculations in the scope of DFT with the goal of describing the electron-hole coupling on the most probable configurations obtained by UMC. The comparison of our results with previously reported data on the literature suggests that the methodology is well suited for describing transfer integrals of organic semiconductors. The observed accuracy together with the smaller computational cost required by our approach allows us to conclude that such methodology might be an important tool towards the description of systems with higher complexity.

  1. Generation of Attosecond Light Pulses from Gas and Solid State Media

    Directory of Open Access Journals (Sweden)

    Stefanos Chatziathanasiou

    2017-03-01

    Full Text Available Real-time observation of ultrafast dynamics in the microcosm is a fundamental approach for understanding the internal evolution of physical, chemical and biological systems. Tools for tracing such dynamics are flashes of light with duration comparable to or shorter than the characteristic evolution times of the system under investigation. While femtosecond (fs pulses are successfully used to investigate vibrational dynamics in molecular systems, real time observation of electron motion in all states of matter requires temporal resolution in the attosecond (1 attosecond (asec = 10−18 s time scale. During the last decades, continuous efforts in ultra-short pulse engineering led to the development of table-top sources which can produce asec pulses. These pulses have been synthesized by using broadband coherent radiation in the extreme ultraviolet (XUV spectral region generated by the interaction of matter with intense fs pulses. Here, we will review asec pulses generated by the interaction of gas phase media and solid surfaces with intense fs IR laser fields. After a brief overview of the fundamental process underlying the XUV emission form these media, we will review the current technology, specifications and the ongoing developments of such asec sources.

  2. Volkov transform generalized projection algorithm for attosecond pulse characterization

    International Nuclear Information System (INIS)

    Keathley, P D; Bhardwaj, S; Moses, J; Laurent, G; Kärtner, F X

    2016-01-01

    An algorithm for characterizing attosecond extreme ultraviolet pulses that is not bandwidth-limited, requires no interpolation of the experimental data, and makes no approximations beyond the strong-field approximation is introduced. This approach fully incorporates the dipole transition matrix element into the retrieval process. Unlike attosecond retrieval methods such as phase retrieval by omega oscillation filtering (PROOF), or improved PROOF, it simultaneously retrieves both the attosecond and infrared (IR) pulses, without placing fundamental restrictions on the IR pulse duration, intensity or bandwidth. The new algorithm is validated both numerically and experimentally, and is also found to have practical advantages. These include an increased robustness to noise, and relaxed requirements for the size of the experimental dataset and the intensity of the streaking pulse. (paper)

  3. Coherent Electron Scattering Captured by an Attosecond Quantum Stroboscope

    International Nuclear Information System (INIS)

    Mauritsson, J.; Johnsson, P.; Mansten, E.; Swoboda, M.; Ruchon, T.; L'Huillier, A.; Schafer, K. J.

    2008-01-01

    We demonstrate a quantum stroboscope based on a sequence of identical attosecond pulses that are used to release electrons into a strong infrared (IR) laser field exactly once per laser cycle. The resulting electron momentum distributions are recorded as a function of time delay between the IR laser and the attosecond pulse train using a velocity map imaging spectrometer. Because our train of attosecond pulses creates a train of identical electron wave packets, a single ionization event can be studied stroboscopically. This technique has enabled us to image the coherent electron scattering that takes place when the IR field is sufficiently strong to reverse the initial direction of the electron motion causing it to rescatter from its parent ion

  4. Electron Interference in Molecular Circular Polarization Attosecond XUV Photoionization

    Directory of Open Access Journals (Sweden)

    Kai-Jun Yuan

    2015-01-01

    Full Text Available Two-center electron interference in molecular attosecond photoionization processes is investigated from numerical solutions of time-dependent Schrödinger equations. Both symmetric H\\(_2^+\\ and nonsymmetric HHe\\(^{2+}\\ one electron diatomic systems are ionized by intense attosecond circularly polarized XUV laser pulses. Photoionization of these molecular ions shows signature of interference with double peaks (minima in molecular attosecond photoelectron energy spectra (MAPES at critical angles \\(\\vartheta_c\\ between the molecular \\(\\textbf{R}\\ axis and the photoelectron momentum \\(\\textbf{p}\\. The interferences are shown to be a function of the symmetry of electronic states and the interference patterns are sensitive to the molecular orientation and pulse polarization. Such sensitivity offers possibility for imaging of molecular structure and orbitals.

  5. Amplitude and phase control of attosecond light pulses

    International Nuclear Information System (INIS)

    Lopez-Martens, Rodrigo; Varju, Katalin; Johnsson, Per; Mauritsson, Johan; Persson, Anders; Svanberg, Sune; Wahlstroem, Claes-Goeran; L'Huillier, Anne; Mairesse, Yann; Salieres, Pascal; Gaarde, Mette B.; Schafer, Kenneth J.

    2005-01-01

    We report the generation, compression, and delivery on target of ultrashort extreme-ultraviolet light pulses using external amplitude and phase control. Broadband harmonic radiation is first generated by focusing an infrared laser with a carefully chosen intensity into a gas cell containing argon atoms. The emitted light then goes through a hard aperture and a thin aluminum filter that selects a 30-eV bandwidth around a 30-eV photon energy and synchronizes all of the components, thereby enabling the formation of a train of almost Fourier-transform-limited single-cycle 170 attosecond pulses. Our experiment demonstrates a practical method for synthesizing and controlling attosecond waveforms

  6. Secondary-electron cascade in attosecond photoelectron spectroscopy from metals

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Madsen, Lars Bojer

    2009-01-01

    an analytical model based on an approximate solution to Boltzmann's transport equation to account for the amount and energy distribution of these secondary electrons. Our theory is in good agreement with the electron spectrum found in a recent attosecond streaking experiment. To suppress the background and gain......Attosecond spectroscopy is currently restricted to photon energies around 100 eV. We show that under these conditions, electron-electron scatterings, as the photoelectrons leave the metal, give rise to a tail of secondary electrons with lower energies and hence a significant background. We develop...

  7. Ponderomotive Generation and Detection of Attosecond Free-Electron Pulse Trains

    Science.gov (United States)

    Kozák, M.; Schönenberger, N.; Hommelhoff, P.

    2018-03-01

    Atomic motion dynamics during structural changes or chemical reactions have been visualized by pico- and femtosecond pulsed electron beams via ultrafast electron diffraction and microscopy. Imaging the even faster dynamics of electrons in atoms, molecules, and solids requires electron pulses with subfemtosecond durations. We demonstrate here the all-optical generation of trains of attosecond free-electron pulses. The concept is based on the periodic energy modulation of a pulsed electron beam via an inelastic interaction, with the ponderomotive potential of an optical traveling wave generated by two femtosecond laser pulses at different frequencies in vacuum. The subsequent dispersive propagation leads to a compression of the electrons and the formation of ultrashort pulses. The longitudinal phase space evolution of the electrons after compression is mapped by a second phase-locked interaction. The comparison of measured and calculated spectrograms reveals the attosecond temporal structure of the compressed electron pulse trains with individual pulse durations of less than 300 as. This technique can be utilized for tailoring and initial characterization of suboptical-cycle free-electron pulses at high repetition rates for stroboscopic time-resolved experiments with subfemtosecond time resolution.

  8. Uncorrelated electron-hole transition energy in GaN|InGaN|GaN spherical QDQW nanoparticles

    International Nuclear Information System (INIS)

    Haddou El Ghazi; Anouar Jorio and Izeddine Zorkani

    2013-01-01

    The electron (hole) energy and uncorrelated 1S e - 1S h electron-hole transition in Core(GaN)|well(In x Ga 1-x N)|shell(GaN) spherical QDQW nanoparticles is investigated as a function of the inner and the outer radii. The calculations are performed within the framework of the effective-mass approximation and the finite parabolic potential confinement barrier in which two confined parameters are taking account. The Indium composition effect is also investigated. A critical value of the outer and the inner ratio is obtained which constitutes the turning point of two indium composition behaviors. (author)

  9. Tricritical behaviour in the phase transition induced by electron-hole pairing

    International Nuclear Information System (INIS)

    Crisan, M.

    1980-01-01

    The electron-hole pairing, which is possible in metals or semiconductors, can give condensed phases with two order parameters. If the coupling between the two order parameters is considered, the free energy functional is similar with the free energy of a n-component spin system with cubic anisotropy. Using the Wagner hypothesis (tricritical scaling) the non-linear scaling fields have been calculated. In order to perform the calculation of the nonlinear fields we used the method given by Rudnick and Nelson to solve the recursion relations for the 4-epsilon-dimensional system with n=6 components. The present calculation in the frame-work of the renormalization-group approach confirms the result obtained in the mean-field theory that the coupling of the two order parameters induces a first order phase transition. (author)

  10. Electron-phonon contribution to the phonon and excited electron (hole) linewidths in bulk Pd

    International Nuclear Information System (INIS)

    Sklyadneva, I Yu; Leonardo, A; Echenique, P M; Eremeev, S V; Chulkov, E V

    2006-01-01

    We present an ab initio study of the electron-phonon (e-ph) coupling and its contribution to the phonon linewidths and to the lifetime broadening of excited electron and hole states in bulk Pd. The calculations, based on density-functional theory, were carried out using a linear-response approach in the plane-wave pseudopotential representation. The obtained results for the Eliashberg spectral function α 2 F(ω), e-ph coupling constant λ, and the contribution to the lifetime broadening, Γ e-ph , show strong dependence on both the energy and momentum of an electron (hole) state. The calculation of phonon linewidths gives, in agreement with experimental observations, an anomalously large broadening for the transverse phonon mode T 1 in the Σ direction. In addition, this mode is found to contribute most strongly to the electron-phonon scattering processes on the Fermi surface

  11. Collisional spin-oriented Sherman function in electron-hole semiconductor plasmas: Landau damping effect

    Science.gov (United States)

    Lee, Myoung-Jae; Jung, Young-Dae

    2018-04-01

    The influence of Landau damping on the spin-oriented collisional asymmetry is investigated in electron-hole semiconductor plasmas. The analytical expressions of the spin-singlet and the spin-triplet scattering amplitudes as well as the spin-oriented asymmetry Sherman function are obtained as functions of the scattering angle, the Landau parameter, the effective Debye length, and the collision energy. It is found that the Landau damping effect enhances the spin-singlet and spin-triplet scattering amplitudes in the forward and back scattering domains, respectively. It is also found that the Sherman function increases with an increase in the Landau parameter. In addition, the spin-singlet scattering process is found to be dominant rather than the spin-triplet scattering process in the high collision energy domain.

  12. The fate of electron-hole pairs in polymer:fullerene blends for organic photovoltaics

    Science.gov (United States)

    Causa', Martina; de Jonghe-Risse, Jelissa; Scarongella, Mariateresa; Brauer, Jan C.; Buchaca-Domingo, Ester; Moser, Jacques-E.; Stingelin, Natalie; Banerji, Natalie

    2016-09-01

    There has been long-standing debate on how free charges are generated in donor:acceptor blends that are used in organic solar cells, and which are generally comprised of a complex phase morphology, where intermixed and neat phases of the donor and acceptor material co-exist. Here we resolve this question, basing our conclusions on Stark effect spectroscopy data obtained in the absence and presence of externally applied electric fields. Reconciling opposing views found in literature, we unambiguously demonstrate that the fate of photogenerated electron-hole pairs--whether they will dissociate to free charges or geminately recombine--is determined at ultrafast times, despite the fact that their actual spatial separation can be much slower. Our insights are important to further develop rational approaches towards material design and processing of organic solar cells, assisting to realize their purported promise as lead-free, third-generation energy technology that can reach efficiencies over 10%.

  13. Nonmonotonic magnetoresistance of a two-dimensional viscous electron-hole fluid in a confined geometry

    Science.gov (United States)

    Alekseev, P. S.; Dmitriev, A. P.; Gornyi, I. V.; Kachorovskii, V. Yu.; Narozhny, B. N.; Titov, M.

    2018-02-01

    Ultrapure conductors may exhibit hydrodynamic transport where the collective motion of charge carriers resembles the flow of a viscous fluid. In a confined geometry (e.g., in ultra-high-quality nanostructures), the electronic fluid assumes a Poiseuille-type flow. Applying an external magnetic field tends to diminish viscous effects leading to large negative magnetoresistance. In two-component systems near charge neutrality, the hydrodynamic flow of charge carriers is strongly affected by the mutual friction between the two constituents. At low fields, the magnetoresistance is negative, however, at high fields the interplay between electron-hole scattering, recombination, and viscosity results in a dramatic change of the flow profile: the magnetoresistance changes its sign and eventually becomes linear in very high fields. This nonmonotonic magnetoresistance can be used as a fingerprint to detect viscous flow in two-component conducting systems.

  14. Theory of laser-assisted autoionization by attosecond light pulses

    International Nuclear Information System (INIS)

    Zhao, Z.X.; Lin, C.D.

    2005-01-01

    We present a quantum theory of the decay of an autoionizing state created in the attosecond xuv (extreme ultraviolet) pump and laser probe measurements within the strong field approximation employing resonance parameters from Fano's theory. From the electron spectra versus the pump-probe time delay, we show how the lifetimes of the resonances can be extracted directly from the time domain measurements

  15. Electron-hole pairs generated in ZrO2 nanoparticle resist upon exposure to extreme ultraviolet radiation

    Science.gov (United States)

    Kozawa, Takahiro; Santillan, Julius Joseph; Itani, Toshiro

    2018-02-01

    Metal oxide nanoparticle resists have attracted much attention as the next-generation resist used for the high-volume production of semiconductor devices. However, the sensitization mechanism of the metal oxide nanoparticle resists is unknown. Understanding the sensitization mechanism is important for the efficient development of resist materials. In this study, the energy deposition in a zirconium oxide (ZrO2) nanoparticle resist was investigated. The numbers of electron-hole pairs generated in a ZrO2 core and an methacrylic acid (MAA) ligand shell upon exposure to 1 mJ cm-2 (exposure dose) extreme ultraviolet (EUV) radiations were theoretically estimated to be 0.16 at most and 0.04-0.17 cm2 mJ-1, respectively. By comparing the calculated distribution of electron-hole pairs with the line-and-space patterns of the ZrO2 nanoparticle resist fabricated by an EUV exposure tool, the number of electron-hole pairs required for the solubility change of the resist films was estimated to be 1.3-2.2 per NP. NP denotes a nanoparticle consisting of a metal oxide core with a ligand shell. In the material design of metal oxide nanoparticle resists, it is important to efficiently use the electron-hole pairs generated in the metal oxide core for the chemical change of ligand molecules.

  16. Electronic hole localization in rutile and anatase TiO2 - Self-interaction correction in Delta-SCF DFT

    DEFF Research Database (Denmark)

    Zawadzki, Pawel; Jacobsen, Karsten Wedel; Rossmeisl, Jan

    2011-01-01

    We study electronic hole localization in rutile and anatase titanium dioxide by means of Δ-Self-Consistent Field Density Functional Theory. In order to compare stabilities of the localized and the delocalized hole states we introduce a simple correction to the wrong description of the localizatio...

  17. G-factors and diamagnetic coefficients of electrons, holes, and excitons in InAs/InP quantum dots

    NARCIS (Netherlands)

    Bree, van J.; Silov, A.Yu.; Koenraad, P.M.; Flatté, M.E.; Pryor, C.E.

    2012-01-01

    The electron, hole, and exciton g factors and diamagnetic coefficients have been calculated using envelope-function theory for cylindrical InAs/InP quantum dots in the presence of a magnetic field parallel to the dot symmetry axis. A clear connection is established between the electron g factor and

  18. Design and Analysis of CMOS-Compatible III-V Compound Electron-Hole Bilayer Tunneling Field-Effect Transistor for Ultra-Low-Power Applications.

    Science.gov (United States)

    Kim, Sung Yoon; Seo, Jae Hwa; Yoon, Young Jun; Lee, Ho-Young; Lee, Seong Min; Cho, Seongjae; Kang, In Man

    2015-10-01

    In this work, we design and analyze complementary metal-oxide-semiconductor (CMOS)-compatible III-V compound electron-hole bilayer (EHB) tunneling field-effect transistors (TFETs) by using two-dimensional (2D) technology computer-aided design (TCAD) simulations. A recently proposed EHB TFET exploits a bias-induced band-to-band tunneling (BTBT) across the electron-hole bilayer by an electric field from the top and bottom gates. This is in contrast to conventional planar p(+)-p(-)-n TFETs, which utilize BTBT across the source-to-channel junction. We applied III-V compound semiconductor materials to the EHB TFETs in order to enhance the current drivability and switching performance. Devices based on various compound semiconductor materials have been designed and analyzed in terms of their primary DC characteristics. In addition, the operational principles were validated by close examination of the electron concentrations and energy-band diagrams under various operation conditions. The simulation results of the optimally designed In0.533Ga0.47As EHB TFET show outstanding performance, with an on-state current (Ion) of 249.5 μA/μm, subthreshold swing (S) of 11.4 mV/dec, and threshold voltage (Vth) of 50 mV at VDS = 0.5 V. Based on the DC-optimized InGaAs EHB TFET, the CMOS inverter circuit was simulated in views of static and dynamic behaviors of the p-channel device with exchanges between top and bottom gates or between source and drain electrodes maintaining the device structure.

  19. Excitonic and electron-hole mechanisms of the creation of Frenkel defect in alkali halides

    International Nuclear Information System (INIS)

    Lushchik, A.; Kirm, M.; Lushchik, Ch.; Vasil'chenko, E.

    2000-01-01

    Excitonic and electron-hole (e-h) mechanisms of stable F centre creation by VUV radiation in alkali halide crystals are discussed. In KCl at 4.2 K, the efficiency of stable F-H pair creation is especially high at the direct optical formation of triplet excitons with n=1. At 200-400 K, the creation processes of stable F centres in KCl are especially efficient at the formation of one-halide exciton in the Urbach tail of an exciton absorption. In KCl and KBr, the decay of a cation exciton (∼20 eV) causes the formation of two e-h pairs, while in NaCl a cation exciton (33.5 eV) decays into two e-h and an anion exciton. An elastic uniaxial stress of a crystal excited by VUV radiation decreases the mean free path of excitons before their self-trapping (KI) and increases the mean free path of hot holes before self-trapping (NaCl)

  20. Order enables efficient electron-hole separation at an organic heterojunction with a small energy loss

    KAUST Repository

    Menke, S. Matthew

    2018-01-12

    Donor–acceptor organic solar cells often show low open-circuit voltages (VOC) relative to their optical energy gap (Eg) that limit power conversion efficiencies to ~12%. This energy loss is partly attributed to the offset between Eg and that of intermolecular charge transfer (CT) states at the donor–acceptor interface. Here we study charge generation occurring in PIPCP:PC61BM, a system with a very low driving energy for initial charge separation (Eg−ECT ~ 50 meV) and a high internal quantum efficiency (ηIQE ~ 80%). We track the strength of the electric field generated between the separating electron-hole pair by following the transient electroabsorption optical response, and find that while localised CT states are formed rapidly (<100 fs) after photoexcitation, free charges are not generated until 5 ps after photogeneration. In PIPCP:PC61BM, electronic disorder is low (Urbach energy <27 meV) and we consider that free charge separation is able to outcompete trap-assisted non-radiative recombination of the CT state.

  1. Berry phase dependent quantum trajectories of electron-hole pairs in semiconductors under intense terahertz fields

    Science.gov (United States)

    Yang, Fan; Liu, Ren-Bao

    2013-03-01

    Quantum evolution of particles under strong fields can be approximated by the quantum trajectories that satisfy the stationary phase condition in the Dirac-Feynmann path integrals. The quantum trajectories are the key concept to understand strong-field optics phenomena, such as high-order harmonic generation (HHG), above-threshold ionization (ATI), and high-order terahertz siedeband generation (HSG). The HSG in semiconductors may have a wealth of physics due to the possible nontrivial ``vacuum'' states of band materials. We find that in a spin-orbit-coupled semiconductor, the cyclic quantum trajectories of an electron-hole pair under a strong terahertz field accumulates nontrivial Berry phases. We study the monolayer MoS2 as a model system and find that the Berry phases are given by the Faraday rotation angles of the pulse emission from the material under short-pulse excitation. This result demonstrates an interesting Berry phase dependent effect in the extremely nonlinear optics of semiconductors. This work is supported by Hong Kong RGC/GRF 401512 and the CUHK Focused Investments Scheme.

  2. Resonant third-harmonic generation of a short-pulse laser from electron-hole plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Kant, Niti [Department of Physics, Lovely Professional University, Phagwara, Punjab 144 402 (India); Nandan Gupta, Devki [Department of Physics and Astrophysics, University of Delhi, Delhi 110 007 (India); Suk, Hyyong [Advanced Photonics Research Institute (APRI) and Graduate Program of Photonics and Applied Physics, Gwangju Institute of Science and Technology, Gwangju 500 712 (Korea, Republic of)

    2012-01-15

    In semiconductors, free carriers are created in pairs in inter-band transitions and consist of an electron and its corresponding hole. At very high carrier densities, carrier-carrier collisions dominate over carrier-lattice collisions and carriers begin to behave collectively to form plasma. Here, we apply a short-pulse laser to generate third-harmonic radiation from a semiconductor plasma (electron-hole plasma) in the presence of a transverse wiggler magnetic-field. The process of third-harmonic generation of an intense short-pulse laser is resonantly enhanced by the magnetic wiggler, i.e., wiggler magnetic field provides the necessary momentum to third-harmonic photons. In addition, a high-power laser radiation, propagating through a semiconductor imparts an oscillatory velocity to the electrons and exerts a ponderomotive force on electrons at the third-harmonic frequency of the laser. This oscillatory velocity produces a third-harmonic longitudinal current. And due to the beating of the longitudinal electron velocity and the wiggler magnetic field, a transverse third-harmonic current is produced that drives third-harmonic electromagnetic radiation. It is finally observed that for a specific wiggler wave number value, the phase-matching conditions for the process are satisfied, leading to resonant enhancement in the energy conversion efficiency.

  3. Resonant third-harmonic generation of a short-pulse laser from electron-hole plasmas

    International Nuclear Information System (INIS)

    Kant, Niti; Nandan Gupta, Devki; Suk, Hyyong

    2012-01-01

    In semiconductors, free carriers are created in pairs in inter-band transitions and consist of an electron and its corresponding hole. At very high carrier densities, carrier-carrier collisions dominate over carrier-lattice collisions and carriers begin to behave collectively to form plasma. Here, we apply a short-pulse laser to generate third-harmonic radiation from a semiconductor plasma (electron-hole plasma) in the presence of a transverse wiggler magnetic-field. The process of third-harmonic generation of an intense short-pulse laser is resonantly enhanced by the magnetic wiggler, i.e., wiggler magnetic field provides the necessary momentum to third-harmonic photons. In addition, a high-power laser radiation, propagating through a semiconductor imparts an oscillatory velocity to the electrons and exerts a ponderomotive force on electrons at the third-harmonic frequency of the laser. This oscillatory velocity produces a third-harmonic longitudinal current. And due to the beating of the longitudinal electron velocity and the wiggler magnetic field, a transverse third-harmonic current is produced that drives third-harmonic electromagnetic radiation. It is finally observed that for a specific wiggler wave number value, the phase-matching conditions for the process are satisfied, leading to resonant enhancement in the energy conversion efficiency.

  4. Harvesting multiple electron-hole pairs generated through plasmonic excitation of Au nanoparticles.

    Science.gov (United States)

    Kim, Youngsoo; Smith, Jeremy G; Jain, Prashant K

    2018-05-07

    Multi-electron redox reactions, although central to artificial photosynthesis, are kinetically sluggish. Amidst the search for synthetic catalysts for such processes, plasmonic nanoparticles have been found to catalyse multi-electron reduction of CO 2 under visible light. This example motivates the need for a general, insight-driven framework for plasmonic catalysis of such multi-electron chemistry. Here, we elucidate the principles underlying the extraction of multiple redox equivalents from a plasmonic photocatalyst. We measure the kinetics of electron harvesting from a gold nanoparticle photocatalyst as a function of photon flux. Our measurements, supported by theoretical modelling, reveal a regime where two-electron transfer from the excited gold nanoparticle becomes prevalent. Multiple electron harvesting becomes possible under continuous-wave, visible-light excitation of moderate intensity due to strong interband transitions in gold and electron-hole separation accomplished using a hole scavenger. These insights will help expand the utility of plasmonic photocatalysis beyond CO 2 reduction to other challenging multi-electron, multi-proton transformations such as N 2 fixation.

  5. Bernstein-Greene-Kruskal theory of electron holes in superthermal space plasma

    Science.gov (United States)

    Aravindakshan, Harikrishnan; Kakad, Amar; Kakad, Bharati

    2018-05-01

    Several spacecraft missions have observed electron holes (EHs) in Earth's and other planetary magnetospheres. These EHs are modeled with the stationary solutions of Vlasov-Poisson equations, obtained by adopting the Bernstein-Greene-Kruskal (BGK) approach. Through the literature survey, we find that the BGK EHs are modelled by using either thermal distribution function or any statistical distribution derived from particular spacecraft observations. However, Maxwell distributions are quite rare in space plasmas; instead, most of these plasmas are superthermal in nature and generally described by kappa distribution. We have developed a one-dimensional BGK model of EHs for space plasma that follows superthermal kappa distribution. The analytical solution of trapped electron distribution function for such plasmas is derived. The trapped particle distribution function in plasma following kappa distribution is found to be steeper and denser as compared to that for Maxwellian distribution. The width-amplitude relation of perturbation for superthermal plasma is derived and allowed regions of stable BGK solutions are obtained. We find that the stable BGK solutions are better supported by superthermal plasmas compared to that of thermal plasmas for small amplitude perturbations.

  6. Order enables efficient electron-hole separation at an organic heterojunction with a small energy loss

    KAUST Repository

    Menke, S. Matthew; Cheminal, Alexandre; Conaghan, Patrick; Ran, Niva A.; Greehnam, Neil C.; Bazan, Guillermo C.; Nguyen, Thuc-Quyen; Rao, Akshay; Friend, Richard H.

    2018-01-01

    Donor–acceptor organic solar cells often show low open-circuit voltages (VOC) relative to their optical energy gap (Eg) that limit power conversion efficiencies to ~12%. This energy loss is partly attributed to the offset between Eg and that of intermolecular charge transfer (CT) states at the donor–acceptor interface. Here we study charge generation occurring in PIPCP:PC61BM, a system with a very low driving energy for initial charge separation (Eg−ECT ~ 50 meV) and a high internal quantum efficiency (ηIQE ~ 80%). We track the strength of the electric field generated between the separating electron-hole pair by following the transient electroabsorption optical response, and find that while localised CT states are formed rapidly (<100 fs) after photoexcitation, free charges are not generated until 5 ps after photogeneration. In PIPCP:PC61BM, electronic disorder is low (Urbach energy <27 meV) and we consider that free charge separation is able to outcompete trap-assisted non-radiative recombination of the CT state.

  7. Giant electron-hole transport asymmetry in ultra-short quantum transistors

    Science.gov (United States)

    McRae, A. C.; Tayari, V.; Porter, J. M.; Champagne, A. R.

    2017-01-01

    Making use of bipolar transport in single-wall carbon nanotube quantum transistors would permit a single device to operate as both a quantum dot and a ballistic conductor or as two quantum dots with different charging energies. Here we report ultra-clean 10 to 100 nm scale suspended nanotube transistors with a large electron-hole transport asymmetry. The devices consist of naked nanotube channels contacted with sections of tube under annealed gold. The annealed gold acts as an n-doping top gate, allowing coherent quantum transport, and can create nanometre-sharp barriers. These tunnel barriers define a single quantum dot whose charging energies to add an electron or a hole are vastly different (e−h charging energy asymmetry). We parameterize the e−h transport asymmetry by the ratio of the hole and electron charging energies ηe−h. This asymmetry is maximized for short channels and small band gap tubes. In a small band gap device, we demonstrate the fabrication of a dual functionality quantum device acting as a quantum dot for holes and a much longer quantum bus for electrons. In a 14 nm-long channel, ηe−h reaches up to 2.6 for a device with a band gap of 270 meV. The charging energies in this device exceed 100 meV. PMID:28561024

  8. Correlation induced electron-hole asymmetry in quasi- two-dimensional iridates.

    Science.gov (United States)

    Pärschke, Ekaterina M; Wohlfeld, Krzysztof; Foyevtsova, Kateryna; van den Brink, Jeroen

    2017-09-25

    The resemblance of crystallographic and magnetic structures of the quasi-two-dimensional iridates Ba 2 IrO 4 and Sr 2 IrO 4 to La 2 CuO 4 points at an analogy to cuprate high-Tc superconductors, even if spin-orbit coupling is very strong in iridates. Here we examine this analogy for the motion of a charge (hole or electron) added to the antiferromagnetic ground state. We show that correlation effects render the hole and electron case in iridates very different. An added electron forms a spin polaron, similar to the cuprates, but the situation of a removed electron is far more complex. Many-body 5d 4 configurations form which can be singlet and triplet states of total angular momentum that strongly affect the hole motion. This not only has ramifications for the interpretation of (inverse-)photoemission experiments but also demonstrates that correlation physics renders electron- and hole-doped iridates fundamentally different.Some iridate compounds such as Sr 2 IrO 4 have electronic and atomic structures similar to quasi-2D copper oxides, raising the prospect of high temperature superconductivity. Here, the authors show that there is significant electron-hole asymmetry in iridates, contrary to expectations from the cuprates.

  9. Low-frequency instabilities of electron-hole plasmas in crossed fields

    International Nuclear Information System (INIS)

    Schneider, W.; Kirchesch, P.

    1978-01-01

    Using local point-contact probes, we observed two types of low-frequency instabilities in n-InSb at 85 K if the samples were exposed to crossed fields. One is a local density instability with threshold frequencies of f = 1 ... 20 Mc, the other a more turbulent current instability. The threshold values of U 0 and B for the onset of these instabilities and the dependence of their amplitudes on the fields have been measured. If a rectangular semiconductor slab is placed in crossed fields, regions of high electric field strength at opposite edges of the contacts are caused by the distortion of the Hall field, giving rise to the generation of electron-hole plasmas by impact ionization. These plasmas are the sources of the observed instabilities. This is especially evident in the case of the local density instability, which originates at the anode high field corner. Several possible reasons for the development of the instabilities are discussed. (orig.) [de

  10. AXSIS: Exploring the frontiers in attosecond X-ray science, imaging and spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kärtner, F.X., E-mail: franz.kaertner@cfel.de [Center for Free-Electron Laser Science, Hamburg (Germany); Institute for Experimental Physics, University of Hamburg, Hamburg (Germany); The Hamburg Center for Ultrafast Imaging, Hamburg (Germany); DESY, Hamburg (Germany); Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA (United States); Ahr, F. [Center for Free-Electron Laser Science, Hamburg (Germany); Institute for Experimental Physics, University of Hamburg, Hamburg (Germany); DESY, Hamburg (Germany); Max Planck Institute for the Structure and Dynamics of Matter, Hamburg (Germany); Calendron, A.-L. [Center for Free-Electron Laser Science, Hamburg (Germany); Institute for Experimental Physics, University of Hamburg, Hamburg (Germany); The Hamburg Center for Ultrafast Imaging, Hamburg (Germany); DESY, Hamburg (Germany); Çankaya, H. [Center for Free-Electron Laser Science, Hamburg (Germany); The Hamburg Center for Ultrafast Imaging, Hamburg (Germany); DESY, Hamburg (Germany); Carbajo, S. [Center for Free-Electron Laser Science, Hamburg (Germany); Institute for Experimental Physics, University of Hamburg, Hamburg (Germany); DESY, Hamburg (Germany); Chang, G.; Cirmi, G. [Center for Free-Electron Laser Science, Hamburg (Germany); The Hamburg Center for Ultrafast Imaging, Hamburg (Germany); DESY, Hamburg (Germany); Dörner, K. [Center for Free-Electron Laser Science, Hamburg (Germany); DESY, Hamburg (Germany); Dorda, U. [DESY, Hamburg (Germany); Fallahi, A. [Center for Free-Electron Laser Science, Hamburg (Germany); DESY, Hamburg (Germany); Hartin, A. [Center for Free-Electron Laser Science, Hamburg (Germany); Institute for Experimental Physics, University of Hamburg, Hamburg (Germany); DESY, Hamburg (Germany); Hemmer, M. [Center for Free-Electron Laser Science, Hamburg (Germany); DESY, Hamburg (Germany); and others

    2016-09-01

    X-ray crystallography is one of the main methods to determine atomic-resolution 3D images of the whole spectrum of molecules ranging from small inorganic clusters to large protein complexes consisting of hundred-thousands of atoms that constitute the macromolecular machinery of life. Life is not static, and unravelling the structure and dynamics of the most important reactions in chemistry and biology is essential to uncover their mechanism. Many of these reactions, including photosynthesis which drives our biosphere, are light induced and occur on ultrafast timescales. These have been studied with high time resolution primarily by optical spectroscopy, enabled by ultrafast laser technology, but they reduce the vast complexity of the process to a few reaction coordinates. In the AXSIS project at CFEL in Hamburg, funded by the European Research Council, we develop the new method of attosecond serial X-ray crystallography and spectroscopy, to give a full description of ultrafast processes atomically resolved in real space and on the electronic energy landscape, from co-measurement of X-ray and optical spectra, and X-ray diffraction. This technique will revolutionize our understanding of structure and function at the atomic and molecular level and thereby unravel fundamental processes in chemistry and biology like energy conversion processes. For that purpose, we develop a compact, fully coherent, THz-driven attosecond X-ray source based on coherent inverse Compton scattering off a free-electron crystal, to outrun radiation damage effects due to the necessary high X-ray irradiance required to acquire diffraction signals. This highly synergistic project starts from a completely clean slate rather than conforming to the specifications of a large free-electron laser (FEL) user facility, to optimize the entire instrumentation towards fundamental measurements of the mechanism of light absorption and excitation energy transfer. A multidisciplinary team formed by laser

  11. Attosecond control of electron beams at dielectric and absorbing membranes

    Science.gov (United States)

    Morimoto, Yuya; Baum, Peter

    2018-03-01

    Ultrashort electron pulses are crucial for time-resolved electron diffraction and microscopy of the fundamental light-matter interaction. In this work, we study experimentally and theoretically the generation and characterization of attosecond electron pulses by optical-field-driven compression and streaking at dielectric or absorbing interaction elements. The achievable acceleration and deflection gradient depends on the laser-electron angle, the laser's electric and magnetic field directions, and the foil orientation. Electric and magnetic fields have similar contributions to the final effect and both need to be considered. Experiments and theory agree well and reveal the optimum conditions for highly efficient, velocity-matched electron-field interactions in the longitudinal or transverse direction. We find that metallic membranes are optimum for light-electron control at mid-infrared or terahertz wavelengths, but dielectric membranes are excellent in the visible and near-infrared regimes and are therefore ideal for the formation of attosecond electron pulses.

  12. Attosecond pulse trains from long laser-gas interaction targets

    International Nuclear Information System (INIS)

    Hauri, C.P.; Lopez-Martens, R.; Varju, K.; Ruchon, T.; Gustafsson, E.; L'Huillier, A.

    2006-01-01

    Complete test of publication follows. Many experiments in attosecond physics require high XUV photon flux as well as a clean attosecond pulse train (APT) temporal structure. Temporal characterization of high-order harmonic generation (HHG) in long interaction targets is thus of high interest. HHG being a very inefficient process, a large effort has been made to increase the amount of XUV photons emitted per infrared laser pulse. Besides quasi phase-matching in a modulated capillary, loose driving laser focusing conditions and subsequent self-channeling have shown to significantly increase the conversion efficiency. We characterized the temporal structure of APTs generated during the self-channeling of an intense IR driving laser pulse. Our first results indicate, however, that the temporal structure of the APT generated during the HHG process might be affected by quantum path interference and spectral phase distortion due to the self-channeling process itself. In particular, our measurements show that the relative spectral phase between consecutive harmonics can strongly vary depending on the target length and the position of the laser focus with respect to the target. In general for short gas targets, no clean APT structure can be expected since the individual attosecond pulses carry significant chirp. For longer targets, however, we observe a flattening of the harmonic spectral phase, resulting in near-transform-limited attosecond pulse trains. A complete analysis of the process is complex and involves detailed knowledge of the spatial and temporal evolution of the self-channeling driver laser pulse throughout the gas target.

  13. Molecular alignment dependent electron interference in attosecond ultraviolet photoionization

    Directory of Open Access Journals (Sweden)

    Kai-Jun Yuan

    2015-01-01

    Full Text Available We present molecular photoionization processes by intense attosecond ultraviolet laser pulses from numerical solutions of time-dependent Schrödinger equations. Simulations preformed on a single electron diatomic H2+ show minima in molecular photoelectron energy spectra resulting from two center interference effects which depend strongly on molecular alignment. We attribute such sensitivity to the spatial orientation asymmetry of the photoionization process from the two nuclei. A similar influence on photoelectron kinetic energies is also presented.

  14. Molecular alignment dependent electron interference in attosecond ultraviolet photoionization

    Science.gov (United States)

    Yuan, Kai-Jun; Bandrauk, André D.

    2015-01-01

    We present molecular photoionization processes by intense attosecond ultraviolet laser pulses from numerical solutions of time-dependent Schrödinger equations. Simulations preformed on a single electron diatomic H2+ show minima in molecular photoelectron energy spectra resulting from two center interference effects which depend strongly on molecular alignment. We attribute such sensitivity to the spatial orientation asymmetry of the photoionization process from the two nuclei. A similar influence on photoelectron kinetic energies is also presented. PMID:26798785

  15. Attosecond delays in photoionization: time and quantum mechanics

    International Nuclear Information System (INIS)

    Maquet, Alfred; Caillat, Jérémie; Taïeb, Richard

    2014-01-01

    This article addresses topics regarding time measurements performed on quantum systems. The motivation is linked to the advent of ‘attophysics’ which makes feasible to follow the motion of electrons in atoms and molecules, with time resolution at the attosecond (1 as = 10 −18 s) level, i.e. at the natural scale for electronic processes in these systems. In this context, attosecond ‘time-delays’ have been recently measured in experiments on photoionization and the question arises if such advances could cast a new light on the still active discussion on the status of the time variable in quantum mechanics. One issue still debatable is how to decide whether one can define a quantum time operator with eigenvalues associated to measurable ‘time-delays’, or time is a parameter, as it is implicit in the Newtonian classical mechanics. One objective of this paper is to investigate if the recent attophysics-based measurements could shed light on this parameter–operator conundrum. To this end, we present here the main features of the theory background, followed by an analysis of the experimental schemes that have been used to evidence attosecond ‘time-delays’ in photoionization. Our conclusion is that these results reinforce the view that time is a parameter which cannot be defined without reference to classical mechanics. (tutorial)

  16. Diffraction and microscopy with attosecond electron pulse trains

    Science.gov (United States)

    Morimoto, Yuya; Baum, Peter

    2018-03-01

    Attosecond spectroscopy1-7 can resolve electronic processes directly in time, but a movie-like space-time recording is impeded by the too long wavelength ( 100 times larger than atomic distances) or the source-sample entanglement in re-collision techniques8-11. Here we advance attosecond metrology to picometre wavelength and sub-atomic resolution by using free-space electrons instead of higher-harmonic photons1-7 or re-colliding wavepackets8-11. A beam of 70-keV electrons at 4.5-pm de Broglie wavelength is modulated by the electric field of laser cycles into a sequence of electron pulses with sub-optical-cycle duration. Time-resolved diffraction from crystalline silicon reveals a propagates in space and time. This unification of attosecond science with electron microscopy and diffraction enables space-time imaging of light-driven processes in the entire range of sample morphologies that electron microscopy can access.

  17. Observation of suppressed Auger mechanism in type-I quantum well structures with delocalized electron-hole wavefunctions

    Energy Technology Data Exchange (ETDEWEB)

    Hassani Nia, Iman; Fathipour, Vala; Mohseni, Hooman, E-mail: hmohseni@ece.northwestern.edu [Bio-Inspired Sensors and Optoelectronics Laboratory (BISOL), Department of Electrical Engineering, Northwestern University, Evanston, Illinois 60208 (United States)

    2015-08-15

    We report the first observation of non-threshold Auger mechanism for a quantum well structure with Type-I band alignment. Excitation-dependent photoluminescence measurements were used to extract the Auger recombination coefficients from 77 K up to room temperature. The results verify the role of interface mediated momentum exchange as well as suppression of Auger recombination for delocalized electron-hole wavefunctions.

  18. Electron-hole pairing and anomalous properties of layered high-Tc compounds

    International Nuclear Information System (INIS)

    Efetov, K.B.

    1991-01-01

    Band-structure pictures for layered high-T c materials available in the literature show that, besides the dispersive broad band responsible for metallic properties, there are at least two additional bands having minima and maxima near the Fermi surface. These additional bands belong to different planes (for example, CuO planes and BiO planes in Bi 2 Sr 2 CaCu 2 O 8 ) or to planes and chains (in YBa 2 Cu 3 O 7 ). Provided the Coulomb repulsion is not very weak, pairing of electrons and holes belonging to these additional bands in different planes or planes and chains is possible. It is shown that, if this possibility is realized, a transition in the additional bands into a state of an excitonic dielectric occurs. The spin of an electron-hole pair can be both 0 and 1. Due to the fact that the electron and the hole of the pair belong to different planes, there are no charge- or spin-density waves. This excitonic insulator can serve as a polarizing substance and give a strong attraction between electrons of the metallic band even if the bare interaction is repulsive. It is also shown that some interesting gapless excitations exist. Provided there are impurities in the system that scatter from plane to plane, these excitations are coupled to the electrons of the metallic band. This effective interaction can be described in terms of an effective mode P(ω) with ImP(ω)∼-sgnω. As a result, one can obtain such properties of the normal state as a linear dependence of the resistivity on temperature, linear dependence of the density of states on energy, constant background in the Raman-scattering intensity, large nuclear relaxation rate, etc., which are very well known from experiments

  19. Phase diagram of a symmetric electron-hole bilayer system: a variational Monte Carlo study.

    Science.gov (United States)

    Sharma, Rajesh O; Saini, L K; Bahuguna, Bhagwati Prasad

    2018-05-10

    We study the phase diagram of a symmetric electron-hole bilayer system at absolute zero temperature and in zero magnetic field within the quantum Monte Carlo approach. In particular, we conduct variational Monte Carlo simulations for various phases, i.e. the paramagnetic fluid phase, the ferromagnetic fluid phase, the anti-ferromagnetic Wigner crystal phase, the ferromagnetic Wigner crystal phase and the excitonic phase, to estimate the ground-state energy at different values of in-layer density and inter-layer spacing. Slater-Jastrow style trial wave functions, with single-particle orbitals appropriate for different phases, are used to construct the phase diagram in the (r s , d) plane by finding the relative stability of trial wave functions. At very small layer separations, we find that the fluid phases are stable, with the paramagnetic fluid phase being particularly stable at [Formula: see text] and the ferromagnetic fluid phase being particularly stable at [Formula: see text]. As the layer spacing increases, we first find that there is a phase transition from the ferromagnetic fluid phase to the ferromagnetic Wigner crystal phase when d reaches 0.4 a.u. at r s   =  20, and before there is a return to the ferromagnetic fluid phase when d approaches 1 a.u. However, for r s   Wigner crystal is stable over the considered range of r s and d. We also find that as r s increases, the critical layer separations for Wigner crystallization increase.

  20. Spin polarized and density modulated phases in symmetric electron-electron and electron-hole bilayers.

    Science.gov (United States)

    Kumar, Krishan; Moudgil, R K

    2012-10-17

    We have studied symmetric electron-electron and electron-hole bilayers to explore the stable homogeneous spin phase and the feasibility of inhomogeneous charge-/spin-density ground states. The former is resolved by comparing the ground-state energies in states of different spin polarizations, while the latter is resolved by searching for a divergence in the wavevector-dependent static charge/spin susceptibility. For this endeavour, we have used the dielectric approach within the self-consistent mean-field theory of Singwi et al. We find that the inter-layer interactions tend to change an abrupt spin-polarization transition of an isolated layer into a nearly gradual one, even though the partially spin-polarized phases are not clearly stable within the accuracy of our calculation. The transition density is seen to decrease with a reduction in layer spacing, implying a suppression of spin polarization by inter-layer interactions. Indeed, the suppression shows up distinctly in the spin susceptibility computed from the spin-polarization dependence of the ground-state energy. However, below a critical layer spacing, the unpolarized liquid becomes unstable against a charge-density-wave (CDW) ground state at a density preceding full spin polarization, with the transition density for the CDW state increasing on further reduction in the layer spacing. Due to attractive e-h correlations, the CDW state is found to be more pronounced in the e-h bilayer. On the other hand, the static spin susceptibility diverges only in the long-wavelength limit, which simply represents a transition to the homogeneous spin-polarized phase.

  1. Single attosecond pulse from terahertz-assisted high-order harmonic generation

    Science.gov (United States)

    Balogh, Emeric; Kovacs, Katalin; Dombi, Peter; Fulop, Jozsef A.; Farkas, Gyozo; Hebling, Janos; Tosa, Valer; Varju, Katalin

    2011-08-01

    High-order harmonic generation by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to generate single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse generation from 23 to 93 eV. We demonstrate that phase-matching effects are responsible for the generation of isolated attosecond pulses, even in conditions when single-atom response yields an attosecond pulse train.

  2. Single attosecond pulse from terahertz-assisted high-order harmonic generation

    International Nuclear Information System (INIS)

    Balogh, Emeric; Kovacs, Katalin; Dombi, Peter; Farkas, Gyozo; Fulop, Jozsef A.; Hebling, Janos; Tosa, Valer; Varju, Katalin

    2011-01-01

    High-order harmonic generation by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to generate single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse generation from 23 to 93 eV. We demonstrate that phase-matching effects are responsible for the generation of isolated attosecond pulses, even in conditions when single-atom response yields an attosecond pulse train.

  3. Single attosecond pulse from terahertz-assisted high-order harmonic generation

    Energy Technology Data Exchange (ETDEWEB)

    Balogh, Emeric [Department of Optics and Quantum Electronics, University of Szeged, H-6701 Szeged (Hungary); Kovacs, Katalin [Department of Optics and Quantum Electronics, University of Szeged, H-6701 Szeged (Hungary); National Institute for R and D of Isotopic and Molecular Technologies, RO-400293 Cluj-Napoca (Romania); Dombi, Peter; Farkas, Gyozo [Research Institute for Solid State Physics and Optics, H-1525 Budapest (Hungary); Fulop, Jozsef A.; Hebling, Janos [Department of Experimental Physics, University of Pecs, H-7624 Pecs (Hungary); Tosa, Valer [National Institute for R and D of Isotopic and Molecular Technologies, RO-400293 Cluj-Napoca (Romania); Varju, Katalin [HAS Research Group on Laser Physics, University of Szeged, H-6701 Szeged (Hungary)

    2011-08-15

    High-order harmonic generation by few-cycle 800 nm laser pulses in neon gas in the presence of a strong terahertz (THz) field is investigated numerically with propagation effects taken into account. Our calculations show that the combination of THz fields with up to 12 fs laser pulses can be an effective gating technique to generate single attosecond pulses. We show that in the presence of the strong THz field only a single attosecond burst can be phase matched, whereas radiation emitted during other half cycles disappears during propagation. The cutoff is extended and a wide supercontinuum appears in the near-field spectra, extending the available spectral width for isolated attosecond pulse generation from 23 to 93 eV. We demonstrate that phase-matching effects are responsible for the generation of isolated attosecond pulses, even in conditions when single-atom response yields an attosecond pulse train.

  4. Producing High Intense Attosecond Pulse Train by Interaction of Three-Color Pulse and Overdense Plasma

    Science.gov (United States)

    Salehi, M.; Mirzanejad, S.

    2017-05-01

    Amplifying the attosecond pulse by the chirp pulse amplification method is impossible. Furthermore, the intensity of attosecond pulse is low in the interaction of laser pulse and underdense plasma. This motivates us to propose using a multi-color pulse to produce the high intense attosecond pulse. In the present study, the relativistic interaction of a three-color linearly-polarized laser-pulse with highly overdense plasma is studied. We show that the combination of {{ω }}1, {{ω }}2 and {{ω }}3 frequencies decreases the instance full width at half maximum reflected attosecond pulse train from the overdense plasma surface. Moreover, we show that the three-color pulse increases the intensity of generated harmonics, which is explained by the relativistic oscillating mirror model. The obtained results demonstrate that if the three-color laser pulse interacts with overdense plasma, it will enhance two orders of magnitude of intensity of ultra short attosecond pulses in comparison with monochromatic pulse.

  5. Exchange electron-hole interaction of two-dimensional magnetoexcitons under the influence of the Rashba spin-orbit coupling

    International Nuclear Information System (INIS)

    Moskalenko, S.A.; Podlesny, I.V.; Lelyakov, I.A.; Novikov, B.V.; Kiselyova, E.S.; Gherciu, L.

    2011-01-01

    The Rashba spin-orbit coupling (RSOC) in the case of two-dimensional (2D) electrons and holes in a strong perpendicular magnetic field was studied. The spinor-type wave functions are characterized by different numbers of Landau levels in different spin projections. For electrons they differ by 1 as was established earlier by Rashba, whereas for holes they differ by 3. Two lowest electron states and four lowest hole states of Landau quantization give rise to eight 2D magnetoexciton states. The exchange electron-hole interaction in the frame of these states is investigated.

  6. Carrier-envelope phase-stabilized attosecond pulses from asymmetric molecules

    International Nuclear Information System (INIS)

    Lan Pengfei; Lu Peixiang; Cao Wei; Li Yuhua; Wang Xinlin

    2007-01-01

    High-order harmonic generation from asymmetric molecules is investigated, and the concept of phase-stabilized infrared ultrashort laser pulses is extended to the extreme ultraviolet regime. It is shown that the ionization symmetry in consecutive half optical cycles is broken for asymmetric molecules, and both even and odd harmonics with comparable intensity are produced. In the time domain, only one attosecond pulse is generated in each cycle of the driving field, and the carrier-envelope phases of the attosecond pulses are equal. Consequently, a clean attosecond pulse train with the same carrier-envelope phase from pulse to pulse is obtained in the extreme ultraviolet regime

  7. Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

    International Nuclear Information System (INIS)

    Ma, Guangjin; Dallari, William; Borot, Antonin; Tsakiris, George D.; Veisz, Laszlo; Krausz, Ferenc; Yu, Wei

    2015-01-01

    We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ∼100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach

  8. A novel strategy to increase separated electron-hole dipoles in commercial Si based solar panel to assist photovoltaic effect

    Science.gov (United States)

    Feng, Yefeng; He, Cheng-En; Xu, Zhichao; Hu, Jianbing; Peng, Cheng

    2018-01-01

    Interface induced polarization has been found to have a significant impact on dielectric properties of 2-2 type polymer composites bearing Si based semi-conducting ceramic sheets. Inherent overall polarity of polymer layers in 2-2 composites has been verified to be closely connected with interface effect and achieved permittivity in composites. In present work, conducting performances of monocrystalline Si sheets coated by varied high polarity material layers were deeply researched. The positive results inspired us to propose a novel strategy to improve separated electron-hole dipoles in commercial Si based solar cell panel for assisting photovoltaic effect, based on strong interface induced polarization. Conducting features of solar panels coated by two different high polarity polymer layers were detected to be greatly elevated compared with solar panel standalone, thanks to interface induced polarization between panel and polymer. Polymer coating with higher polarity would lead to more separated electron-hole dipole pairs in solar panel contributing to higher conductivity of panel. Valid synergy of interface effect and photovoltaic effect was based on their unidirectional traits of electron transfer. Dielectric properties of solar panels in composites further confirmed that strategy. This work might provide a facile route to prepare promising Si based solar panels with higher photoelectric conversion efficiency by enhancing interface induced polarization between panel and polymer coating.

  9. Attosecond Electron Processes in Materials: Excitons, Plasmons, and Charge Dynamics

    Science.gov (United States)

    2015-05-19

    focused using a f=1.5 m lens into a 250 micron hollow core fiber (HCF) filled with neon gas at atmospheric pressure to stretch the pulse spectrum from... insulator to metal transition. Introduction: The goal of this work was to understand the generation, transport, and manipulation of electronic charge...chemically sensitive probe pulse utilizing specific core level transitions in atoms that are part of a material under study. The measurements follow

  10. Attosecond-correlated dynamics of two electrons in argon

    Indian Academy of Sciences (India)

    2014-01-11

    Jan 11, 2014 ... 2Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany ... involving a highly correlated electronic transition state. ... laser is low, the recolliding electron can have a maximum energy of about 15 eV which.

  11. Negligible Electronic Interaction between Photoexcited Electron-Hole Pairs and Free Electrons in Phosphorus-Boron Co-Doped Silicon Nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Limpens, Rens [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Neale, Nathan R [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Fujii, Minoru [Kobe University; Gregorkiewicz, Tom [University of Amsterdam

    2018-03-05

    Phosphorus (P) and boron (B) co-doped Si nanocrystals (NCs) have raised interest in the optoelectronic industry due to their electronic tunability, optimal carrier multiplication properties, and straightforward dispersibility in polar solvents. Yet a basic understanding of the interaction of photoexcited electron-hole (e-h) pairs with new physical features that are introduced by the co-doping process (free carriers, defect states, and surface chemistry) is missing. Here, we present the first study of the ultrafast carrier dynamics in SiO2-embedded P-B co-doped Si NC ensembles using induced absorption spectroscopy through a two-step approach. First, the induced absorption data show that the large fraction of the dopants residing on the NC surface slows down carrier relaxation dynamics within the first 20 ps relative to intrinsic (undoped) Si NCs, which we interpret as enhanced surface passivation. On longer time-scales (picosecond to nanosecond regime), we observe a speeding up of the carrier relaxation dynamics and ascribe it to doping-induced trap states. This argument is deduced from the second part of the study, where we investigate multiexciton interactions. From a stochastic modeling approach we show that localized carriers, which are introduced by the P or B dopants, have minor electronic interactions with the photoexcited e-h pairs. This is understood in light of the strong localization of the introduced carriers on their original P- or B-dopant atoms, due to the strong quantum confinement regime in these relatively small NCs (<6 nm).

  12. Attosecond time delay in the valence photoionization of C240 versus C60

    International Nuclear Information System (INIS)

    Shi, Kele; Magrakvelidze, Maia; Anstine, Dylan; Chakraborty, Himadri; Madjet, Mohamed

    2015-01-01

    We investigate effects of electron correlations on the attosecond time delay of the photoionization from HOMO and HOMO-1 electrons in C 240 . A comparison with earlier C 60 results assesses the molecular size effect. (paper)

  13. Mapping the spectral phase of isolated attosecond pulses by extreme-ultraviolet emission spectrum.

    Science.gov (United States)

    Liu, Candong; Zeng, Zhinan; Li, Ruxin; Xu, Zhizhan; Nisoli, Mauro

    2015-04-20

    An all-optical method is proposed for the measurement of the spectral phase of isolated attosecond pulses. The technique is based on the generation of extreme-ultraviolet (XUV) radiation in a gas by the combination of an attosecond pulse and a strong infrared (IR) pulse with controlled electric field. By using a full quantum simulation, we demonstrate that, for particular temporal delays between the two pulses, the IR field can drive back to the parent ions the photoelectrons generated by the attosecond pulse, thus leading to the generation of XUV photons. It is found that the generated XUV spectrum is notably sensitive to the chirp of the attosecond pulse, which can then be reliably retrieved. A classical quantum-path analysis is further used to quantitatively explain the main features exhibited in the XUV emission.

  14. Attosecond time-energy structure of X-ray free-electron laser pulses

    Science.gov (United States)

    Hartmann, N.; Hartmann, G.; Heider, R.; Wagner, M. S.; Ilchen, M.; Buck, J.; Lindahl, A. O.; Benko, C.; Grünert, J.; Krzywinski, J.; Liu, J.; Lutman, A. A.; Marinelli, A.; Maxwell, T.; Miahnahri, A. A.; Moeller, S. P.; Planas, M.; Robinson, J.; Kazansky, A. K.; Kabachnik, N. M.; Viefhaus, J.; Feurer, T.; Kienberger, R.; Coffee, R. N.; Helml, W.

    2018-04-01

    The time-energy information of ultrashort X-ray free-electron laser pulses generated by the Linac Coherent Light Source is measured with attosecond resolution via angular streaking of neon 1s photoelectrons. The X-ray pulses promote electrons from the neon core level into an ionization continuum, where they are dressed with the electric field of a circularly polarized infrared laser. This induces characteristic modulations of the resulting photoelectron energy and angular distribution. From these modulations we recover the single-shot attosecond intensity structure and chirp of arbitrary X-ray pulses based on self-amplified spontaneous emission, which have eluded direct measurement so far. We characterize individual attosecond pulses, including their instantaneous frequency, and identify double pulses with well-defined delays and spectral properties, thus paving the way for X-ray pump/X-ray probe attosecond free-electron laser science.

  15. Feasibility analysis for attosecond X-ray pulses at FERMI@ELETTRA free electron laser

    Energy Technology Data Exchange (ETDEWEB)

    Zholents, Alexander

    2004-09-01

    We present preliminary analysis for the feasibility of the attosecond x-ray pulses at a proposed FERMI@ELETTRA free electron laser (FEL) [1]. In part 1 we restrict ourselves to minimal modifications to the proposed FEL and consider a scheme for attosecond x-ray production which can be qualified as a small add-on to a primary facility. We demonstrate that at 5-nm wavelength our scheme is capable for production of pulses with an approximate duration of 100 attoseconds at approximately 2 MW peak power and with an absolute temporal synchronization to a pump laser pulse. In part 2 we propose to use an FEL amplifier seeded by a VUV signal and to follow it by the scheme for attosecond x-ray production described in part 1.

  16. Attosecond Coherent Control of the Photo-Dissociation of Oxygen Molecules

    Science.gov (United States)

    Sturm, Felix; Ray, Dipanwita; Wright, Travis; Shivaram, Niranjan; Bocharova, Irina; Slaughter, Daniel; Ranitovic, Predrag; Belkacem, Ali; Weber, Thorsten

    2016-05-01

    Attosecond Coherent Control has emerged in recent years as a technique to manipulate the absorption and ionization in atoms as well as the dissociation of molecules on an attosecond time scale. Single attosecond pulses and attosecond pulse trains (APTs) can coherently excite multiple electronic states. The electronic and nuclear wave packets can then be coupled with a second pulse forming multiple interfering quantum pathways. We have built a high flux extreme ultraviolet (XUV) light source delivering APTs based on HHG that allows to selectively excite neutral and ion states in molecules. Our beamline provides spectral selectivity and attosecond interferometric control of the pulses. In the study presented here, we use APTs, generated by High Harmonic Generation in a high flux extreme ultraviolet light source, to ionize highly excited states of oxygen molecules. We identify the ionization/dissociation pathways revealing vibrational structure with ultra-high resolution ion 3D-momentum imaging spectroscopy. Furthermore, we introduce a delay between IR pulses and XUV/IR pulses to constructively or destructively interfere the ionization and dissociation pathways, thus, enabling the manipulation of both the O2+and the O+ ion yields with attosecond precision. Supported by DOE under Contract No. DE-AC02-05CH11231.

  17. Electron-hole transition in spherical QD-QW nanoparticles based on GaN∣(In,Ga)N∣GaN under hydrostatic pressure

    International Nuclear Information System (INIS)

    El Ghazi, Haddou; Jorio, Anouar

    2013-01-01

    Within the framework of effective-mass approximation and finite parabolic potential confinement barrier in which two confinement parameters are taking account, the electron (hole) energy and the ground-state electron-hole (e−h) transition in Core∣well∣shell (GaN|In x Ga 1−x N|GaN) spherical QD-QW nanoparticles are investigated as a function of the inner and the outer radii under externally applied hydrostatic pressure. The pressure dependencies of the effective-mass and the QD radius are taking into account. The results we obtained are in quite good agreement with the theoretical and the experimental findings

  18. Electron-hole transition in spherical QD-QW nanoparticles based on GaN∣(In,Ga)N∣GaN under hydrostatic pressure

    Energy Technology Data Exchange (ETDEWEB)

    El Ghazi, Haddou, E-mail: hadghazi@gmail.com [LPS, Faculty of Science, Dhar EL Mehrez, BP 1796 Fes-Atlas (Morocco); Special Mathematics, CPGE Kénitra, Chakib Arsalane Street (Morocco); Jorio, Anouar [LPS, Faculty of Science, Dhar EL Mehrez, BP 1796 Fes-Atlas (Morocco)

    2013-11-15

    Within the framework of effective-mass approximation and finite parabolic potential confinement barrier in which two confinement parameters are taking account, the electron (hole) energy and the ground-state electron-hole (e−h) transition in Core∣well∣shell (GaN|In{sub x}Ga{sub 1−x}N|GaN) spherical QD-QW nanoparticles are investigated as a function of the inner and the outer radii under externally applied hydrostatic pressure. The pressure dependencies of the effective-mass and the QD radius are taking into account. The results we obtained are in quite good agreement with the theoretical and the experimental findings.

  19. Observation of topological surface states and strong electron/hole imbalance in extreme magnetoresistance compound LaBi

    Science.gov (United States)

    Jiang, J.; Schröter, N. B. M.; Wu, S.-C.; Kumar, N.; Shekhar, C.; Peng, H.; Xu, X.; Chen, C.; Yang, H. F.; Hwang, C.-C.; Mo, S.-K.; Felser, C.; Yan, B. H.; Liu, Z. K.; Yang, L. X.; Chen, Y. L.

    2018-02-01

    The recent discovery of the extreme magnetoresistance (XMR) in the nonmagnetic rare-earth monopnictides La X (X = P, As, Sb, Bi,), a recently proposed new topological semimetal family, has inspired intensive research effort in the exploration of the correlation between the XMR and their electronic structures. In this work, using angle-resolved photoemission spectroscopy to investigate the three-dimensional band structure of LaBi, we unraveled its topologically nontrivial nature with the observation of multiple topological surface Dirac fermions, as supported by our ab initio calculations. Furthermore, we observed substantial imbalance between the volume of electron and hole pockets, which rules out the electron-hole compensation as the primary cause of the XMR in LaBi.

  20. Optical circular deflector with attosecond resolution for ultrashort electron beam

    Directory of Open Access Journals (Sweden)

    Zhen Zhang

    2017-05-01

    Full Text Available A novel method using high-power laser as a circular deflector is proposed for the measurement of femtosecond (fs and sub-fs electron beam. In the scheme, the electron beam interacts with a laser pulse operating in a radially polarized doughnut mode (TEM_{01^{*}} in a helical undulator, generating angular kicks along the beam in two directions at the same time. The phase difference between the two angular kicks makes the beam form a ring after a propagation section with appropriate phase advance, which can reveal the current profile of the electron beam. Detailed theoretical analysis of the method and numerical results with reasonable parameters are both presented. It is shown that the temporal resolution can reach up to ∼100 attosecond, which is a significant improvement for the diagnostics of ultrashort electron beam.

  1. Mesoscopic chaos mediated by Drude electron-hole plasma in silicon optomechanical oscillators

    Science.gov (United States)

    Wu, Jiagui; Huang, Shu-Wei; Huang, Yongjun; Zhou, Hao; Yang, Jinghui; Liu, Jia-Ming; Yu, Mingbin; Lo, Guoqiang; Kwong, Dim-Lee; Duan, Shukai; Wei Wong, Chee

    2017-01-01

    Chaos has revolutionized the field of nonlinear science and stimulated foundational studies from neural networks, extreme event statistics, to physics of electron transport. Recent studies in cavity optomechanics provide a new platform to uncover quintessential architectures of chaos generation and the underlying physics. Here, we report the generation of dynamical chaos in silicon-based monolithic optomechanical oscillators, enabled by the strong and coupled nonlinearities of two-photon absorption induced Drude electron–hole plasma. Deterministic chaotic oscillation is achieved, and statistical and entropic characterization quantifies the chaos complexity at 60 fJ intracavity energies. The correlation dimension D2 is determined at 1.67 for the chaotic attractor, along with a maximal Lyapunov exponent rate of about 2.94 times the fundamental optomechanical oscillation for fast adjacent trajectory divergence. Nonlinear dynamical maps demonstrate the subharmonics, bifurcations and stable regimes, along with distinct transitional routes into chaos. This provides a CMOS-compatible and scalable architecture for understanding complex dynamics on the mesoscopic scale. PMID:28598426

  2. Research Update: Relativistic origin of slow electron-hole recombination in hybrid halide perovskite solar cells

    Directory of Open Access Journals (Sweden)

    Pooya Azarhoosh

    2016-09-01

    Full Text Available The hybrid perovskite CH3NH3PbI3 (MAPI exhibits long minority-carrier lifetimes and diffusion lengths. We show that slow recombination originates from a spin-split indirect-gap. Large internal electric fields act on spin-orbit-coupled band extrema, shifting band-edges to inequivalent wavevectors, making the fundamental gap indirect. From a description of photoluminescence within the quasiparticle self-consistent GW approximation for MAPI, CdTe, and GaAs, we predict carrier lifetime as a function of light intensity and temperature. At operating conditions we find radiative recombination in MAPI is reduced by a factor of more than 350 compared to direct gap behavior. The indirect gap is retained with dynamic disorder.

  3. Research Update: Relativistic origin of slow electron-hole recombination in hybrid halide perovskite solar cells

    Science.gov (United States)

    Azarhoosh, Pooya; McKechnie, Scott; Frost, Jarvist M.; Walsh, Aron; van Schilfgaarde, Mark

    2016-09-01

    The hybrid perovskite CH3NH3PbI3 (MAPI) exhibits long minority-carrier lifetimes and diffusion lengths. We show that slow recombination originates from a spin-split indirect-gap. Large internal electric fields act on spin-orbit-coupled band extrema, shifting band-edges to inequivalent wavevectors, making the fundamental gap indirect. From a description of photoluminescence within the quasiparticle self-consistent GW approximation for MAPI, CdTe, and GaAs, we predict carrier lifetime as a function of light intensity and temperature. At operating conditions we find radiative recombination in MAPI is reduced by a factor of more than 350 compared to direct gap behavior. The indirect gap is retained with dynamic disorder.

  4. Determination of the electron-hole pair creation energy for semiconductors from the spectral responsivity of photodiodes

    CERN Document Server

    Scholze, F; Kuschnerus, P; Rabus, H; Richter, M; Ulm, G

    2000-01-01

    Ionizing radiation can be detected by the measurement of the charge carriers produced in a detector. The improved semiconductor technology now allows detectors operating near the physical limits of the detector materials to be designed. The mean energy required for producing an electron-hole pair, W, is a material property of the semiconductor. Here, the determination of W from the spectral responsivity of photodiodes is demonstrated. Using spectrally dispersed synchrotron radiation, different types of semiconductor photodiodes have been examined in the UV-, VUV-, and soft X-ray spectral range. Their spectral responsivity was determined with relative uncertainties between 0.4% and 1% using a cryogenic electrical-substitution radiometer as primary detector standard. Results are presented for silicon n-on-p junction photodiodes and for GaAsP/Au Schottky diodes at room temperature. The investigations for silicon covered the complete spectral range from 3 to 1500 eV, yielding a constant value W=(3.66+-0.03) eV fo...

  5. Two-particle self-consistent analysis for the electron-hole asymmetry of superconductivity in cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Ogura, Daisuke; Kuroki, Kazuhiko [Department of Physics, Graduate School of Science, Osaka University, Toyonaka (Japan)

    2017-06-15

    In the hole-doped type cuprate superconductors, it is well-known that the superconducting transition temperature T{sub c} exhibits a dome-like structure against doping. On the other hand, recent experiments unveil that T{sub c} in the electron-doped compounds shows a monotonic increase with decreasing the doping, at least down to a very small doping rate. Our recent study for the three-band d-p model has unveiled that this asymmetric behavior can be explained as a combined effect of the intrinsic electron-hole asymmetry in systems comprising Cu3 d and O2 p orbitals and the band-filling-dependent vertex correction. In the present study, we study another compound Tl{sub 2} Ba{sub 2} CuO{sub 6} to show that this explanation can be applied to other cuprate superconductors with the small d{sub z{sup 2}} orbital mixture. By varying the d-p offset, we also study how the strength of the d-p hybridization controls the spin fluctuation and hence the pairing interaction. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. The impact of long-range electron-hole interaction on the charge separation yield of molecular photocells

    Science.gov (United States)

    Nemati Aram, Tahereh; Ernzerhof, Matthias; Asgari, Asghar; Mayou, Didier

    2017-01-01

    We discuss the effects of charge carrier interaction and recombination on the operation of molecular photocells. Molecular photocells are devices where the energy conversion process takes place in a single molecular donor-acceptor complex attached to electrodes. Our investigation is based on the quantum scattering theory, in particular on the Lippmann-Schwinger equation; this minimizes the complexity of the problem while providing useful and non-trivial insight into the mechanism governing photocell operation. In this study, both exciton pair creation and dissociation are treated in the energy domain, and therefore there is access to detailed spectral information, which can be used as a framework to interpret the charge separation yield. We demonstrate that the charge carrier separation is a complex process that is affected by different parameters, such as the strength of the electron-hole interaction and the non-radiative recombination rate. Our analysis helps to optimize the charge separation process and the energy transfer in organic solar cells and in molecular photocells.

  7. Electron, hole and exciton self-trapping in germanium doped silica glass from DFT calculations with self-interaction correction

    International Nuclear Information System (INIS)

    Du Jincheng; Rene Corrales, L.; Tsemekhman, Kiril; Bylaska, Eric J.

    2007-01-01

    Density functional theory (DFT) calculations were employed to understand the refractive index change in germanium doped silica glasses for the trapped states of electronic excitations induced by UV irradiation. Local structure relaxation and excess electron density distribution were calculated upon self-trapping of an excess electron, hole, and exciton in germanium doped silica glass. The results show that both the trapped exciton and excess electron are highly localized on germanium ion and, to some extent, on its oxygen neighbors. Exciton self-trapping is found to lead to the formation of a Ge E' center and a non-bridging hole center. Electron trapping changes the GeO 4 tetrahedron structure into trigonal bi-pyramid with the majority of the excess electron density located along the equatorial line. The self-trapped hole is localized on bridging oxygen ions that are not coordinated to germanium atoms that lead to elongation of the Si-O bonds and change of the Si-O-Si bond angles. We carried out a comparative study of standard DFT versus DFT with a hybrid PBE0 exchange and correlation functional. The results show that the two methods give qualitatively similar relaxed structure and charge distribution for electron and exciton trapping in germanium doped silica glass; however, only the PBE0 functional produces the self-trapped hole

  8. Monte Carlo studies of thermalization of electron-hole pairs in spin-polarized degenerate electron gas in monolayer graphene

    Science.gov (United States)

    Borowik, Piotr; Thobel, Jean-Luc; Adamowicz, Leszek

    2018-02-01

    Monte Carlo method is applied to the study of relaxation of excited electron-hole (e-h) pairs in graphene. The presence of background of spin-polarized electrons, with high density imposing degeneracy conditions, is assumed. To such system, a number of e-h pairs with spin polarization parallel or antiparallel to the background is injected. Two stages of relaxation: thermalization and cooling are clearly distinguished when average particles energy and its standard deviation σ _E are examined. At the very beginning of thermalization phase, holes loose energy to electrons, and after this process is substantially completed, particle distributions reorganize to take a Fermi-Dirac shape. To describe the evolution of and σ _E during thermalization, we define characteristic times τ _ {th} and values at the end of thermalization E_ {th} and σ _ {th}. The dependence of these parameters on various conditions, such as temperature and background density, is presented. It is shown that among the considered parameters, only the standard deviation of electrons energy allows to distinguish between different cases of relative spin polarizations of background and excited electrons.

  9. Scale-invariant puddles in graphene: Geometric properties of electron-hole distribution at the Dirac point.

    Science.gov (United States)

    Najafi, M N; Nezhadhaghighi, M Ghasemi

    2017-03-01

    We characterize the carrier density profile of the ground state of graphene in the presence of particle-particle interaction and random charged impurity in zero gate voltage. We provide detailed analysis on the resulting spatially inhomogeneous electron gas, taking into account the particle-particle interaction and the remote Coulomb disorder on an equal footing within the Thomas-Fermi-Dirac theory. We present some general features of the carrier density probability measure of the graphene sheet. We also show that, when viewed as a random surface, the electron-hole puddles at zero chemical potential show peculiar self-similar statistical properties. Although the disorder potential is chosen to be Gaussian, we show that the charge field is non-Gaussian with unusual Kondev relations, which can be regarded as a new class of two-dimensional random-field surfaces. Using Schramm-Loewner (SLE) evolution, we numerically demonstrate that the ungated graphene has conformal invariance and the random zero-charge density contours are SLE_{κ} with κ=1.8±0.2, consistent with c=-3 conformal field theory.

  10. Assessment of pseudo-bilayer structures in the heterogate germanium electron-hole bilayer tunnel field-effect transistor

    International Nuclear Information System (INIS)

    Padilla, J. L.; Alper, C.; Ionescu, A. M.; Medina-Bailón, C.; Gámiz, F.

    2015-01-01

    We investigate the effect of pseudo-bilayer configurations at low operating voltages (≤0.5 V) in the heterogate germanium electron-hole bilayer tunnel field-effect transistor (HG-EHBTFET) compared to the traditional bilayer structures of EHBTFETs arising from semiclassical simulations where the inversion layers for electrons and holes featured very symmetric profiles with similar concentration levels at the ON-state. Pseudo-bilayer layouts are attained by inducing a certain asymmetry between the top and the bottom gates so that even though the hole inversion layer is formed at the bottom of the channel, the top gate voltage remains below the required value to trigger the formation of the inversion layer for electrons. Resulting benefits from this setup are improved electrostatic control on the channel, enhanced gate-to-gate efficiency, and higher I ON levels. Furthermore, pseudo-bilayer configurations alleviate the difficulties derived from confining very high opposite carrier concentrations in very thin structures

  11. Assessment of pseudo-bilayer structures in the heterogate germanium electron-hole bilayer tunnel field-effect transistor

    Energy Technology Data Exchange (ETDEWEB)

    Padilla, J. L., E-mail: jose.padilladelatorre@epfl.ch; Alper, C.; Ionescu, A. M. [Nanoelectronic Devices Laboratory, École Polytechnique Fédérale de Lausanne, Lausanne CH-1015 (Switzerland); Medina-Bailón, C.; Gámiz, F. [Departamento de Electrónica y Tecnología de los Computadores, Universidad de Granada, Avda. Fuentenueva s/n, 18071 Granada (Spain)

    2015-06-29

    We investigate the effect of pseudo-bilayer configurations at low operating voltages (≤0.5 V) in the heterogate germanium electron-hole bilayer tunnel field-effect transistor (HG-EHBTFET) compared to the traditional bilayer structures of EHBTFETs arising from semiclassical simulations where the inversion layers for electrons and holes featured very symmetric profiles with similar concentration levels at the ON-state. Pseudo-bilayer layouts are attained by inducing a certain asymmetry between the top and the bottom gates so that even though the hole inversion layer is formed at the bottom of the channel, the top gate voltage remains below the required value to trigger the formation of the inversion layer for electrons. Resulting benefits from this setup are improved electrostatic control on the channel, enhanced gate-to-gate efficiency, and higher I{sub ON} levels. Furthermore, pseudo-bilayer configurations alleviate the difficulties derived from confining very high opposite carrier concentrations in very thin structures.

  12. Numerical simulation of evolution of electron-hole avalanches and streamers in silicon in a uniform electric field

    International Nuclear Information System (INIS)

    Kyuregyan, A. S.

    2010-01-01

    Numerical simulation of origination and evolution of streamers in Si is performed for the first time. It is assumed that an external electric field E 0 is constant and uniform, the avalanche and streamer are axially symmetric, and background electrons and holes are absent. The calculations have been performed in the context of the diffusion-drift approximation with impact and tunneling ionization, Auger recombination, and electron-hole scattering taken into account. The most realistic values of the ionization and recombination rates, diffusion coefficients, and drift mobilities of electrons and holes have been used. It is shown that the features of evolution of avalanches and streamers are generally consistent with the result obtained previously for a hypothetic semiconductor with equal kinetic coefficients for electrons and holes. Asymmetry of these coefficients (mostly, the impact-ionization coefficients) manifests itself only at the initial stage of evolution. However, with time, two exponentially self-similar streamers are formed, differing only in the sign of charge of fronts and directions of their propagation. Empirical dependences of the main parameters of streamers on E 0 in the range of 0.34-0.75 MV/cm have been derived for this most important stage of evolution.

  13. Kinematical vortices in double photoionization of helium by attosecond pulses

    Science.gov (United States)

    Djiokap, J. M. Ngoko; Meremianin, A. V.; Manakov, N. L.; Hu, S. X.; Madsen, L. B.; Starace, Anthony F.

    2017-07-01

    Two-armed helical vortex structures are predicted in the two-electron momentum distributions produced in double photoionization (DPI) of the He atom by a pair of time-delayed elliptically polarized attosecond pulses with opposite helicities. These predictions are based upon both a first-order perturbation theory analysis and numerical solutions of the two-electron, time-dependent Schrödinger equation in six spatial dimensions. The helical vortex structures originate from Ramsey interference of a pair of ionized two-electron wave packets, each having a total angular momentum of unity, and appear in the sixfold differential DPI probability distribution for any energy partitioning between the two electrons. The vortex structures are exquisitely sensitive to the time delay between the two pulses, their relative phase, their ellipticity, and their handedness; moreover, they occur in a variety of electron detection geometries. However, the vortex structures only occur when the angular separation β =cos-1(p̂1.p̂2) between the electron momenta p1 and p2 is held fixed. The vortex structures can also be observed in the fourfold differential DPI probability distribution obtained by averaging the sixfold differential probability over the emission angles of one electron. Such kinematical vortices are a general phenomenon that may occur in any ionization process, initiated by two time-delayed short pulses with opposite ellipticities, for particular detection geometries.

  14. Reflection of attosecond x-ray free electron laser pulses

    International Nuclear Information System (INIS)

    Hau-Riege, Stefan P.; Chapman, Henry N.

    2007-01-01

    In order to utilize hard x-ray free electron lasers (XFEL's) when they are extended to attosecond pulse lengths, it is necessary to choose optical elements with minimal response time. Specular grazing-incidence optics made of low-Z materials are popular candidates for reflectors since they are likely to withstand x-ray damage and provide sufficiently large reflectivities. Using linear-optics reflection theory, we calculated the transient reflectivity of a delta-function electric pulse from a homogenous semi-infinite medium as a function of angle of incidence for s- and p-polarized light. We specifically considered the pulse response of beryllium, diamond, silicon carbide, and silicon, all of which are of relevance to the XFEL's that are currently being built. We found that the media emit energy in a damped oscillatory way, and that the impulse-response times are shorter than 0.3 fs for normal incidence. For grazing incidence, the impulse-response time is substantially shorter, making grazing-incidence mirrors a good choice for deep subfemtosecond reflective optics

  15. Energy relaxation and separation of a hot electron-hole pair in organic aggregates from a time-dependent wavepacket diffusion method

    International Nuclear Information System (INIS)

    Han, Lu; Liang, WanZhen; Zhao, Yi; Zhong, Xinxin

    2014-01-01

    The time-dependent wavepacket diffusive method [X. Zhong and Y. Zhao, J. Chem. Phys. 138, 014111 (2013)] is extended to investigate the energy relaxation and separation of a hot electron-hole pair in organic aggregates with incorporation of Coulomb interaction and electron-phonon coupling. The pair initial condition generated by laser pulse is represented by a Gaussian wavepacket with a central momentum. The results reveal that the hot electron energy relaxation is very well described by two rate processes with the fast rate much larger than the slow one, consistent with experimental observations, and an efficient electron-hole separation is accomplished accompanying the fast energy relaxation. Furthermore, although the extra energy indeed helps the separation by overcoming the Coulomb interaction, the width of initial wavepacket is much sensitive to the separation efficiency and the narrower wavepacket generates the more separated charges. This behavior may be useful to understand the experimental controversy of the hot carrier effect on charge separation

  16. Simultaneous effects of electron-hole correlation, hydrostatic pressure, and temperature on the third harmonic generation in parabolic GaAs quantum dots

    International Nuclear Information System (INIS)

    Duque, C. M.; Mora-Ramos, M. E.; Duque, C. A.

    2011-01-01

    The combined effects of electron-hole correlation, hydrostatic pressure, and temperature on the third harmonic generation in disk-shaped parabolic GaAs quantum dots are studied under the density matrix formalism and the effective mass approximation. Two well-defined regimes are discussed: (1) the strong-confinement regime, where the Coulomb interaction between the electron and hole is neglected and (2) the weak-confinement regime where the parabolic confinement term is neglected and the system reaches the limit of a hydrogenic problem. The results show that the third harmonic-generation coefficient is strongly dependent on the localization of the electron-hole pair. Also, that by using external perturbations like hydrostatic pressure or by considering the temperature effects it is possible to induce a blue-shift and/or red-shift on the resonant peaks of the third harmonic generation coefficient.

  17. Attosecond control of orbital parity mix interferences and the relative phase of even and odd harmonics in an attosecond pulse train.

    Science.gov (United States)

    Laurent, G; Cao, W; Li, H; Wang, Z; Ben-Itzhak, I; Cocke, C L

    2012-08-24

    We experimentally demonstrate that atomic orbital parity mix interferences can be temporally controlled on an attosecond time scale. Electron wave packets are formed by ionizing argon gas with a comb of odd and even high-order harmonics, in the presence of a weak infrared field. Consequently, a mix of energy-degenerate even and odd parity states is fed in the continuum by one- and two-photon transitions. These interfere, leading to an asymmetric electron emission along the polarization vector. The direction of the emission can be controlled by varying the time delay between the comb and infrared field pulses. We show that such asymmetric emission provides information on the relative phase of consecutive odd and even order harmonics in the attosecond pulse train.

  18. Generation of Attosecond x-ray pulse using Coherent Relativistic Nonlinear Thomson Scattering

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ki Tae; Park, Seong Hee; Cha, Yong Ho; Jeong, Young Uk; Lee, Byung Cheol [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2005-07-01

    Relativistic plasma, a new regime in physics, has been opened due to the development in ultra-intense laser technology during the past decade. Not only the fundamental aspect of relativistic plasma are attractive but also its potential application seems to be significant especially in the area of the generation of high energy particles such as electrons, ions, positrons, and {gamma}-rays. The generation of x-ray radiation with a pulse width of sub-femtoseconds presently draws much attention because such a radiation allows one to explore ultra-fast dynamics of electrons and nucleons. Several schemes have been proposed and/or demonstrated to generate an ultra-short x-ray pulse: the relativistic Doppler shift of a backscattered laser pulse by a relativistic electron beam, the harmonic frequency upshift of a laser pulse by relativistic nonlinear motion of electrons, high order harmonic generation in the interaction of intense laser pulse with noble gases and solids The train of a few 100 attosecond pulses has been observed in the case of laser-noble gas interaction. When a low-intensity laser pulse is irradiated on an electron, the electron undergoes a harmonic oscillatory motion and generates a dipole radiation with the same frequency as the incident laser pulse, which is called Thomson scattering. As the laser intensity increases, the oscillatory motion of the electron becomes relativistically nonlinear, which leads to the generation of harmonic radiations, referred to as Relativistic Nonlinear Thomson Scattered (RNTS) radiation. The motion of the electron begins to be relativistic as the following normalized vector potential approaches to unity: a{sub 0}=8.5 x 10{sup -10} {lambda}{iota}{sup 1/2} , (1) where {lambda} is the laser wavelength in {mu}m and I the laser intensity in W/cm{sup 2} The RNTS radiation has been investigated in analytical ways. Recently, indebted to the development of the ultra-intense laser pulse, experiments on RNTS radiation have been carried

  19. Fine structure of excitons and electron-hole exchange energy in polymorphic CsPbBr3 single nanocrystals.

    Science.gov (United States)

    Ramade, Julien; Andriambariarijaona, Léon Marcel; Steinmetz, Violette; Goubet, Nicolas; Legrand, Laurent; Barisien, Thierry; Bernardot, Frédérick; Testelin, Christophe; Lhuillier, Emmanuel; Bramati, Alberto; Chamarro, Maria

    2018-04-05

    All inorganic CsPbX3 (X = Cl, Br, I) nanocrystals (NCs) belong to the novel class of confined metal-halide perovskites which are currently arousing enthusiasm and stimulating huge activity across several fields of optoelectronics due to outstanding properties. A deep knowledge of the band-edge excitonic properties of these materials is thus crucial to further optimize their performances. Here, high-resolution photoluminescence (PL) spectroscopy of single bromide-based NCs reveals the exciton fine structure in the form of sharp peaks that are linearly polarized and grouped in doublets or triplets, which directly mirror the adopted crystalline structure, tetragonal (D4h symmetry) or orthorhombic (D2h symmetry). Intelligible equations are found that show how the fundamental parameters (spin-orbit coupling, ΔSO, crystal field term, T, and electron-hole exchange energy, J) rule the energy spacings in doublets and triplets. From experimental data, fine estimations of each parameter are obtained. The analysis of the absorption spectra of an ensemble of NCs with a "quasi-bulk" behavior leads to ΔSO = 1.20 ± 0.06 eV and T = -0.34 ± 0.05 eV in CsPbBr3. The study of individual luminescence responses of NCs having sizes comparable to the exciton Bohr diameter, 7 nm, allows us to estimate the value of J to be around ≈3 meV in both tetragonal and orthorhombic phases. This value is already enhanced by confinement.

  20. Measurement of the attosecond emission from aligned molecules

    International Nuclear Information System (INIS)

    Boutu, W.; Merdji, H.; Fitour, R.; Monchicourt, P.; Breger, P.; Carre, B.; Salieres, P.

    2006-01-01

    Complete test of publication follows. Recently, a number of papers have demonstrated the interest of high-order harmonic generation (HHG) from molecules aligned with respect to the laser polarization. Itatani et al. (Nature 432, 867 (2004)) have shown that a precise characterization of the harmonic emission allows performing a tomographic reconstruction of the molecular orbitals that radiate. Kanai et al. (Nature 435, 470 (2005)) have evidenced quantum interferences in the recombination process of HHG that are directly related to the molecular structure. In all of these papers, only the HHG intensity was measured. The relative harmonic phase, though more difficult to measure, contains important information on the interference process, and is needed for an ab initio tomographic reconstruction. Finally, while the attosecond emission from atoms has been thoroughly studied, in particular by our group (Mairesse et al., Science (302, 1540 (2003)), it has not been investigated in molecules. In a first experiment (Wabnitz et al., EPJD (2006)), we measured the amplitude and relative phase of harmonics radiated by un-aligned nitrogen molecules. Small but reproducible deviations from the phase of harmonics generated in argon (same ionization potential as nitrogen) were measured for low orders. In a recent experiment, we have measured, up to high order, the harmonic amplitude and relative phase for aligned molecules (N 2 and CO 2 ). In order to align the molecules, we used the so-called nonadiabatic technique: a rotational wavepacket is created by a strong enough and short aligning pulse, so that a field-free alignment is obtained at the revival (a few ps after the aligning pulse). The measurement of phase locking between neighboring harmonics was performed through the photoionization of a target gas by the harmonic beam in presence of a sufficiently intense 'dressing' laser beam (RABITT technique). The harmonic phase measured when the CO 2 molecules are aligned parallel to

  1. Optical conductivity calculation of a k.p model semiconductor GaAs incorporating first-order electron-hole vertex correction

    Science.gov (United States)

    Nurhuda, Maryam; Aziz Majidi, Muhammad

    2018-04-01

    The role of excitons in semiconducting materials carries potential applications. Experimental results show that excitonic signals also appear in optical absorption spectra of semiconductor system with narrow gap, such as Gallium Arsenide (GaAs). While on the theoretical side, calculation of optical spectra based purely on Density Functional Theory (DFT) without taking electron-hole (e-h) interactions into account does not lead to the appearance of any excitonic signal. Meanwhile, existing DFT-based algorithms that include a full vertex correction through Bethe-Salpeter equation may reveal an excitonic signal, but the algorithm has not provided a way to analyze the excitonic signal further. Motivated to provide a way to isolate the excitonic effect in the optical response theoretically, we develop a method of calculation for the optical conductivity of a narrow band-gap semiconductor GaAs within the 8-band k.p model that includes electron-hole interactions through first-order electron-hole vertex correction. Our calculation confirms that the first-order e-h vertex correction reveals excitonic signal around 1.5 eV (the band gap edge), consistent with the experimental data.

  2. Interaction of attosecond electromagnetic pulses with atoms: The exactly solvable model

    International Nuclear Information System (INIS)

    Popov, Yu. V.; Kouzakov, K. A.; Vinitsky, S. I.; Gusev, A. A.

    2007-01-01

    We consider the exactly solvable model of interaction of zero-duration electromagnetic pulses with an atom. The model has a number of peculiar properties which are outlined in the cases of a single pulse and two opposite pulses. In perspective, it can be useful in different fields of physics involving interaction of attosecond laser pulses with quantum systems

  3. Interference Processes During Reradiation of Attosecond Pulses of Electromagnetic Field by Graphene

    Science.gov (United States)

    Makarov, D. N.; Matveev, V. I.; Makarova, K. A.

    2018-05-01

    Interference spectra during reradiation of attosecond pulses of electromagnetic field by graphene sheets are considered. Analytical expressions for calculations of spectral distributions are derived. As an example, the interference spectra of a graphene sheet and a flat rectangular lattice are compared.

  4. Laser plasma as a source of intense attosecond pulses via high-order harmonic generation

    International Nuclear Information System (INIS)

    Ozaki, T.

    2013-01-01

    The incredible progress in ultrafast laser technology and Ti:sapphire lasers have lead to many important applications, one of them being high-order harmonic generation (HHG). HHG is a source of coherent extreme ultraviolet (XUV) radiation, which has opened new frontiers in science by extending nonlinear optics and time-resolved spectroscopy to the XUV region, and pushing ultrafast science to the attosecond domain. Progress in attosecond science has revealed many new phenomena that have not been seen with femtosecond pulses. Clearly, the next frontier is to study nonlinear effects at the attosecond timescale and in the XUV. However, a problem with present-day attosecond pulses is that they are just too weak to induce measurable nonlinearities, which severely limits the application of this source. While HHG from solid targets has shown promise for higher conversion efficiency, there is no experiment so far that demonstrates isolated attosecond pulse generation. The generation of isolated, several 100-as pulses with few-µJ energy will enable us to enter a completely new phase in attoscience. In past works, we have demonstrated that high-order harmonics from lowly ionized plasma is a highly efficient method to generate coherent XUV pulses. For example, indium plasma has been shown to generate intense 13th harmonic of the Ti:sapphire laser, with conversion efficiency of 10-4. However, the quasi-monochromatic nature of indium harmonics would make it difficult to generate attosecond pulses. We have also demonstrated that one could increase the harmonic yield by using nanoparticle targets. Specifically, we showed that by using indium oxide nanoparticles or C60 film, we could obtain intense harmonics between wavelengths of 50 to 90 nm. The energy in each of these harmonic orders was measured to be a few µJ, which is sufficient for many applications. However, the problem of using nanoparticle or film targets is the rapid decrease in the harmonic intensity, due to the rapid

  5. Formation of electrostatic double-layers and electron-holes in a low pressure mercury plasma column

    International Nuclear Information System (INIS)

    Petraconi, G; Maciel, Homero S

    2003-01-01

    Experimental studies of the formation of electrostatic double layers (DLs) and electron-holes (e-holes) are reported. The measurements were performed in the positive column of a mercury arc discharge operating in the low-pressure range of (2.0-14.0) x 10 -2 Pa with current density in the range of (3.0-8.0) x 10 3 A m -2 . Stable and unstable modes of the discharge were identified as the current was gradually increased, keeping constant the vapour pressure. The discharge remains stable until a critical current from which a slight increase of the current leads to an unstable regime characterized by high discharge impedance and strong oscillations. This mode ceased after a DL was formed in the plasma column. To induce the DL formation and to transport it smoothly along the discharge column, a low intensity B-field (7-10) x 10 -3 T produced by a movable single coil was used. The B-field locally increases the electron current density and makes the DL form at the centre of the magnetic constriction where it remained at rest. Electrostatic potential structures compatible with ordinary DLs and multiple-layers could be formed in the plasma column by dealing with the combined effects of the operational parameters of the discharge. It is noticeable that a pure e-hole, which is a symmetric triple-layer having a bell shape potential profile, could easily be formed by means of this experimental technique. A partial kinetic description, based on the space charge structure derived from an experimental e-hole, is presented in order to infer the charged particle populations that could contribute to the space charge of the e-hole. Evidence is shown that strong e-hole formation might be driven by an ion beam, therefore it could not be formed in isolation since its formation requires a nearby ion accelerating potential structure. Probe measurements of the plasma properties, at various radial positions of the stable positive column, are also presented. In the stable mode, prior to

  6. Large-scale laser-microwave synchronization for attosecond photon science facilities

    Energy Technology Data Exchange (ETDEWEB)

    Shafak, Kemal

    2017-04-15

    Low-noise transfer of time and frequency standards over large distances provides high temporal resolution for ambitious scientific explorations such as sensitive imaging of astronomical objects using multi-telescope arrays, comparison of distant optical clocks or gravitational-wave detection using large laser interferometers. In particular, rapidly expanding photon science facilities such as X-ray free-electron lasers (FELs) and attoscience centers have the most challenging synchronization requirements of sub-fs timing precision to generate ultrashort X-ray pulses for the benefit of creating super-microscopes with sub-atomic spatiotemporal resolution. The critical task in these facilities is to synchronize various pulsed lasers and microwave sources across multi-kilometer distances as required for seeded FELs and attosecond pump-probe experiments. So far, there has been no timing distribution system meeting this strict requirement. Therefore, insufficient temporal precision provided by the current synchronization systems hinders the development of attosecond hard X-ray photon science facilities. The aim of this thesis is to devise a timing distribution system satisfying the most challenging synchronization requirements in science mandated by the next-generation photon science facilities. Using the pulsed-optical timing distribution approach, attosecond timing precision is realized by thoroughly investigating and eliminating the remaining noise sources in the synchronization system. First, optical and microwave timing detection schemes are further developed to support long-term stable, attosecond-precision measurements. Second, the feasibility of the master laser to support a kilometer-scale timing network with attosecond precision is examined by experimentally characterizing its free-running timing jitter and improving its long-term frequency stability with a sophisticated environmental insulation. Third, nonlinear pulse propagation inside optical fibers is studied

  7. Large-scale laser-microwave synchronization for attosecond photon science facilities

    International Nuclear Information System (INIS)

    Shafak, Kemal

    2017-04-01

    Low-noise transfer of time and frequency standards over large distances provides high temporal resolution for ambitious scientific explorations such as sensitive imaging of astronomical objects using multi-telescope arrays, comparison of distant optical clocks or gravitational-wave detection using large laser interferometers. In particular, rapidly expanding photon science facilities such as X-ray free-electron lasers (FELs) and attoscience centers have the most challenging synchronization requirements of sub-fs timing precision to generate ultrashort X-ray pulses for the benefit of creating super-microscopes with sub-atomic spatiotemporal resolution. The critical task in these facilities is to synchronize various pulsed lasers and microwave sources across multi-kilometer distances as required for seeded FELs and attosecond pump-probe experiments. So far, there has been no timing distribution system meeting this strict requirement. Therefore, insufficient temporal precision provided by the current synchronization systems hinders the development of attosecond hard X-ray photon science facilities. The aim of this thesis is to devise a timing distribution system satisfying the most challenging synchronization requirements in science mandated by the next-generation photon science facilities. Using the pulsed-optical timing distribution approach, attosecond timing precision is realized by thoroughly investigating and eliminating the remaining noise sources in the synchronization system. First, optical and microwave timing detection schemes are further developed to support long-term stable, attosecond-precision measurements. Second, the feasibility of the master laser to support a kilometer-scale timing network with attosecond precision is examined by experimentally characterizing its free-running timing jitter and improving its long-term frequency stability with a sophisticated environmental insulation. Third, nonlinear pulse propagation inside optical fibers is studied

  8. Direct luminescence evidence for the degenerate electron-hole plasma formation in A/sup II/B/sup VI/ semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Brodin, M.S.; Bandura, V.M.; Matsko, M.G. (AN Ukrainskoj SSR, Kiev. Inst. Fiziki)

    1983-09-01

    The emission spectra of ZnTe and ZnSe crystals are investigated at T = 4.2 K at high excitation densities by a Coumarin 30 and 120 dye laser. It is shown that for excitation densities R/sub exc/ > 0.1 MW/cm/sup 2/ the emission spectrum of ZnTe exhibits the P-band due to inelastic exciton-exciton scattering. For R/sub exc/ > 6 MW/cm/sup 2/ the emission of a degenerate electron-hole plasma (EHP) is observed. These emission bands may be differentiated by scanning the exciting quanta energy in the short-wavelength tail region.

  9. Direct luminescence evidence for the degenerate electron-hole plasma formation in A/sup II/B/sup VI/ semiconductors

    International Nuclear Information System (INIS)

    Brodin, M.S.; Bandura, V.M.; Matsko, M.G.

    1983-01-01

    The emission spectra of ZnTe and ZnSe crystals are investigated at T = 4.2 K at high excitation densities by a Coumarin 30 and 120 dye laser. It is shown that for excitation densities R/sub exc/ > 0.1 MW/cm 2 the emission spectrum of ZnTe exhibits the P-band due to inelastic exciton-exciton scattering. For R/sub exc/ > 6 MW/cm 2 the emission of a degenerate electron-hole plasma (EHP) is observed. These emission bands may be differentiated by scanning the exciting quanta energy in the short-wavelength tail region. (author)

  10. Ultrafast quantum control of ionization dynamics in krypton.

    Science.gov (United States)

    Hütten, Konrad; Mittermair, Michael; Stock, Sebastian O; Beerwerth, Randolf; Shirvanyan, Vahe; Riemensberger, Johann; Duensing, Andreas; Heider, Rupert; Wagner, Martin S; Guggenmos, Alexander; Fritzsche, Stephan; Kabachnik, Nikolay M; Kienberger, Reinhard; Bernhardt, Birgitta

    2018-02-19

    Ultrafast spectroscopy with attosecond resolution has enabled the real time observation of ultrafast electron dynamics in atoms, molecules and solids. These experiments employ attosecond pulses or pulse trains and explore dynamical processes in a pump-probe scheme that is selectively sensitive to electronic state of matter via photoelectron or XUV absorption spectroscopy or that includes changes of the ionic state detected via photo-ion mass spectrometry. Here, we demonstrate how the implementation of combined photo-ion and absorption spectroscopy with attosecond resolution enables tracking the complex multidimensional excitation and decay cascade of an Auger auto-ionization process of a few femtoseconds in highly excited krypton. In tandem with theory, our study reveals the role of intermediate electronic states in the formation of multiply charged ions. Amplitude tuning of a dressing laser field addresses different groups of decay channels and allows exerting temporal and quantitative control over the ionization dynamics in rare gas atoms.

  11. Propagation of an attosecond pulse in a dense two-level medium

    International Nuclear Information System (INIS)

    Song Xiaohong; Gong Shangqing; Yang Weifeng; Xu Zhizhan

    2004-01-01

    We investigate the propagation of attosecond pulse in a dense two-level medium by using an iterative predictor-corrector finite-difference time-domain method. We find when attosecond pulse is considered, that the standard area theorem will break down even for small area pulses: ideal self-induced transparency cannot occur even for a 2π pulse, while the pulses whose areas are not integer multiples of 2π, such as 1.8π and 2.2π pulses, cannot evolve to 2π pulses as predicted by the standard area theorem. Significantly higher spectra components can occur on all these small area propagating pulses due to strong carrier reshaping. Furthermore, these higher spectral components dependent sensitively on the pulse area: the larger the pulse area is, the more evident are these higher spectral components

  12. High Harmonic Radiation Generation and Attosecond pulse generation from Intense Laser-Solid Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Alexander Roy [Univ. of Michigan, Ann Arbor, MI (United States); Krushelnick, Karl [Univ. of Michigan, Ann Arbor, MI (United States)

    2016-09-08

    We have studied ion motion effects in high harmonic generation, including shifts to the harmonics which result in degradation of the attosecond pulse train, and how to mitigate them. We have examined the scaling with intensity of harmonic emission. We have also switched the geometry of the interaction to measure, for the first time, harmonics from a normal incidence interaction. This was performed by using a special parabolic reflector with an on axis hole and is to allow measurements of the attosecond pulses using standard techniques. Here is a summary of the findings: First high harmonic generation in laser-solid interactions at 1021 Wcm-2, demonstration of harmonic focusing, study of ion motion effects in high harmonic generation in laser-solid interactions, and demonstration of harmonic amplification.

  13. Generation of attosecond soft X-ray pulses in a longitudinal space charge amplifier

    Energy Technology Data Exchange (ETDEWEB)

    Dohlus, M.; Schneidmiller, E.A.; Yurkov, M.V. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2011-03-15

    A longitudinal space charge amplifier (LSCA), operating in soft X-ray regime, was recently proposed. Such an amplifier consists of a few amplification cascades (focusing channel and chicane) and a short radiator undulator in the end. Broadband nature of LSCA supports generation of few-cycle pulses as well as wavelength compression. In this paper we consider an application of these properties of LSCA for generation of attosecond X-ray pulses. It is shown that a compact and cheap addition to the soft X-ray free electron laser facility FLASH would allow to generate 60 attosecond (FWHM) long X-ray pulses with the peak power at 100 MW level and a contrast above 98%. (orig.)

  14. Generation of attosecond soft X-ray pulses in a longitudinal space charge amplifier

    International Nuclear Information System (INIS)

    Dohlus, M.; Schneidmiller, E.A.; Yurkov, M.V.

    2011-03-01

    A longitudinal space charge amplifier (LSCA), operating in soft X-ray regime, was recently proposed. Such an amplifier consists of a few amplification cascades (focusing channel and chicane) and a short radiator undulator in the end. Broadband nature of LSCA supports generation of few-cycle pulses as well as wavelength compression. In this paper we consider an application of these properties of LSCA for generation of attosecond X-ray pulses. It is shown that a compact and cheap addition to the soft X-ray free electron laser facility FLASH would allow to generate 60 attosecond (FWHM) long X-ray pulses with the peak power at 100 MW level and a contrast above 98%. (orig.)

  15. Obtaining attosecond x-ray pulses using a self-amplified spontaneous emission free electron laser

    Directory of Open Access Journals (Sweden)

    A. A. Zholents

    2005-05-01

    Full Text Available We describe a technique for the generation of a solitary attosecond x-ray pulse in a free-electron laser (FEL, via a process of self-amplified spontaneous emission. In this method, electrons experience an energy modulation upon interacting with laser pulses having a duration of a few cycles within single-period wiggler magnets. Two consecutive modulation sections, followed by compression in a dispersive section, are used to obtain a single, subfemtosecond spike in the electron peak current. This region of the electron beam experiences an enhanced growth rate for FEL amplification. After propagation through a long undulator, this current spike emits a ∼250   attosecond x-ray pulse whose intensity dominates the x-ray emission from the rest of the electron bunch.

  16. Generation of attosecond soft x-ray pulses in a longitudinal space charge amplifier

    Directory of Open Access Journals (Sweden)

    M. Dohlus

    2011-09-01

    Full Text Available A longitudinal space charge amplifier (LSCA, operating in soft x-ray regime, was recently proposed. Such an amplifier consists of a few amplification cascades (focusing channel and chicane and a short radiator undulator in the end. The broadband nature of LSCA supports generation of few-cycle pulses as well as wavelength compression. In this paper we consider an application of these properties of LSCA for generation of attosecond x-ray pulses. It is shown that a compact and cheap addition to the soft x-ray free-electron laser facility FLASH would allow one to generate 60 attosecond (FWHM long x-ray pulses with the peak power at the 100 MW level and a contrast above 98%.

  17. Generation of attosecond electron packets via conical surface plasmon electron acceleration

    Science.gov (United States)

    Greig, S. R.; Elezzabi, A. Y.

    2016-01-01

    We present a method for the generation of high kinetic energy attosecond electron packets via magnetostatic and aperture filtering of conical surface plasmon (SP) accelerated electrons. The conical SP waves are excited by coupling an ultrafast radially polarized laser beam to a conical silica lens coated with an Ag film. Electromagnetic and particle tracking models are employed to characterize the ultrafast electron packets. PMID:26764129

  18. Generation of an isolated sub-30 attosecond pulse in a two-color laser field and a static electric field

    International Nuclear Information System (INIS)

    Zhang Gang-Tai; Zhang Mei-Guang; Bai Ting-Ting

    2012-01-01

    We theoretically investigate high-order harmonic generation (HHG) from a helium ion model in a two-color laser field, which is synthesized by a fundamental pulse and its second harmonic pulse. It is shown that a supercontinuum spectrum can be generated in the two-color field. However, the spectral intensity is very low, limiting the application of the generated attosecond (as) pulse. By adding a static electric field to the synthesized two-color field, not only is the ionization yield of electrons contributing to the harmonic emission remarkably increased, but also the quantum paths of the HHG can be significantly modulated. As a result, the extension and enhancement of the supercontinuum spectrum are achieved, producing an intense isolated 26-as pulse with a bandwidth of about 170.5 eV. In particular, we also analyse the influence of the laser parameters on the ultrabroad supercontinuum spectrum and isolated sub-30-as pulse generation. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  19. News and views from the attosecond generation, characterization and applications frontier

    International Nuclear Information System (INIS)

    Tzallas, P.; Kalpouzos, C.; Kruse, J.; Skatzakis, E.; Charalambidis, D.

    2010-01-01

    Complete text of publication follows. We report on recent results in the generation, characterization and applications of energetic attosecond pulse trains and ultra-broad coherent XUV continua: 1) Generation: 1a) We report experimental results confirming contribution of both long and short trajectories in on-axis harmonic generation before, at and after an atomic gas jet, i.e. under three different phase matching conditions. The contribution of both trajectories is manifested through their interference leading to a modulated harmonic (and side band) yield as a function of the driving intensity. 1b) We report the generation of sub-fs pulse trains at the 40 μJ pulse energy level from laser surface plasma, measured through 2 nd order intensity volume autocorrelation (2 nd order IVAC). 2) Characterization: We present comparative studies between RABITT and 2 nd order IVAC in on axis harmonic generation before, at and after an atomic gas jet. We find that the two techniques give fairly different results that are compatible with the differently weighted but unavoidable presence of the long and short trajectory in the generation process in all three phase matching conditions. We show that the relative contributions of the two trajectories can be estimated through RABITT measurements, while spatiotemporal mean pulse durations can be extracted from 2 nd order IVAC traces. 3) Applications: 3a) We present time resolved VUV spectroscopy of ultrafast dynamics in molecular ethylene. 3b) We present time resolved XUV spectroscopy at the 1 fs temporal scale and ultra-broad band XUV Fourier Transform Spectroscopy in a manifold of doubly excited autoionizing and inner-shell Auger decaying states excited simultaneously through a coherent broadband XUV continuum. Acknowledgments. This work is supported in part by the European Community's Human Potential Program under contract MTKD-CT-2004-517145 (X-HOMES), the Ultraviolet Laser Facility (ULF) operating at FORTH-IESL (contract PHRI

  20. Generation of isolated attosecond pulses using a plasmonic funnel-waveguide

    International Nuclear Information System (INIS)

    Choi, Joonhee; Kim, Seungchul; Park, In-Yong; Lee, Dong-Hyub; Han, Seunghwoi; Kim, Seung-Woo

    2012-01-01

    We theoretically investigated the possibility of generating attosecond pulses by means of plasmonic field enhancement induced in a nano-structured metallic funnel-waveguide. This study was motivated by our recent experimental demonstration of ultrashort extreme-ultraviolet (EUV) pulses using the same type of three-dimensional waveguides. Here, with emphasis on generation of isolated attosecond pulses, the finite-domain time-difference method was used to analyze the funnel-waveguide with respect to the geometry-dependent plasmonic features such as the field enhancement factor, enhanced plasmonic field profile and hot-spot location. Then an extended semi-classical model of high-order harmonic generation was adopted to predict the EUV spectra generated from the funnel-waveguide in consideration of the spatial inhomogeneity of the plasmonic field within the hot-spot volume. Our simulation finally proved that isolated attosecond pulses can be produced at fast repetition rates directly from a few-cycle femtosecond laser or by synthesizing a two-color laser consisting of two multi-cycle pulses of cross-polarized configuration. (paper)

  1. Charge-compensation in 3d-transition-metal-oxide intercalation cathodes through the generation of localized electron holes on oxygen.

    Science.gov (United States)

    Luo, Kun; Roberts, Matthew R; Hao, Rong; Guerrini, Niccoló; Pickup, David M; Liu, Yi-Sheng; Edström, Kristina; Guo, Jinghua; Chadwick, Alan V; Duda, Laurent C; Bruce, Peter G

    2016-07-01

    During the charging and discharging of lithium-ion-battery cathodes through the de- and reintercalation of lithium ions, electroneutrality is maintained by transition-metal redox chemistry, which limits the charge that can be stored. However, for some transition-metal oxides this limit can be broken and oxygen loss and/or oxygen redox reactions have been proposed to explain the phenomenon. We present operando mass spectrometry of (18)O-labelled Li1.2[Ni0.13(2+)Co0.13(3+)Mn0.54(4+)]O2, which demonstrates that oxygen is extracted from the lattice on charging a Li1.2[Ni0.13(2+)Co0.13(3+)Mn0.54(4+)]O2 cathode, although we detected no O2 evolution. Combined soft X-ray absorption spectroscopy, resonant inelastic X-ray scattering spectroscopy, X-ray absorption near edge structure spectroscopy and Raman spectroscopy demonstrates that, in addition to oxygen loss, Li(+) removal is charge compensated by the formation of localized electron holes on O atoms coordinated by Mn(4+) and Li(+) ions, which serve to promote the localization, and not the formation, of true O2(2-) (peroxide, O-O ~1.45 Å) species. The quantity of charge compensated by oxygen removal and by the formation of electron holes on the O atoms is estimated, and for the case described here the latter dominates.

  2. Atomic and molecular dynamics triggered by ultrashort light pulses on the atto- to picosecond time scale

    Science.gov (United States)

    Pabst, Stefan

    2013-04-01

    Time-resolved investigations of ultrafast electronic and molecular dynamics were not possible until recently. The typical time scale of these processes is in the picosecond to attosecond realm. The tremendous technological progress in recent years made it possible to generate ultrashort pulses, which can be used to trigger, to watch, and to control atomic and molecular motion. This tutorial focuses on experimental and theoretical advances which are used to study the dynamics of electrons and molecules in the presence of ultrashort pulses. In the first part, the rotational dynamics of molecules, which happens on picosecond and femtosecond time scales, is reviewed. Well-aligned molecules are particularly suitable for angle-dependent investigations like x-ray diffraction or strong-field ionization experiments. In the second part, the ionization dynamics of atoms is studied. The characteristic time scale lies, here, in the attosecond to few-femtosecond regime. Although a one-particle picture has been successfully applied to many processes, many-body effects do constantly occur. After a broad overview of the main mechanisms and the most common tools in attosecond physics, examples of many-body dynamics in the attosecond world (e.g., in high-harmonic generation and attosecond transient absorption spectroscopy) are discussed.

  3. Direct-Bandgap InAs Quantum-Dots Have Long-Range Electron--Hole Exchange Whereas Indirect Gap Si Dots Have Short-Range Exchange

    International Nuclear Information System (INIS)

    Juo, J.W.; Franceschetti, A.; Zunger, A.

    2009-01-01

    Excitons in quantum dots manifest a lower-energy spin-forbidden 'dark' state below a spin-allowed 'bright' state; this splitting originates from electron-hole (e-h) exchange interactions, which are strongly enhanced by quantum confinement. The e-h exchange interaction may have both a short-range and a long-range component. Calculating numerically the e-h exchange energies from atomistic pseudopotential wave functions, we show here that in direct-gap quantum dots (such as InAs) the e-h exchange interaction is dominated by the long-range component, whereas in indirect-gap quantum dots (such as Si) only the short-range component survives. As a result, the exciton dark/bright splitting scales as 1/R 2 in InAs dots and 1/R 3 in Si dots, where R is the quantum-dot radius.

  4. Characterization of a quadrant diamond transmission X-ray detector including a precise determination of the mean electron-hole pair creation energy.

    Science.gov (United States)

    Keister, Jeffrey W; Cibik, Levent; Schreiber, Swenja; Krumrey, Michael

    2018-03-01

    Precise monitoring of the incoming photon flux is crucial for many experiments using synchrotron radiation. For photon energies above a few keV, thin semiconductor photodiodes can be operated in transmission for this purpose. Diamond is a particularly attractive material as a result of its low absorption. The responsivity of a state-of-the art diamond quadrant transmission detector has been determined, with relative uncertainties below 1% by direct calibration against an electrical substitution radiometer. From these data and the measured transmittance, the thickness of the involved layers as well as the mean electron-hole pair creation energy were determined, the latter with an unprecedented relative uncertainty of 1%. The linearity and X-ray scattering properties of the device are also described.

  5. Phosphate Changes Effect of Humic Acids on TiO2 Photocatalysis: From Inhibition to Mitigation of Electron-Hole Recombination.

    Science.gov (United States)

    Long, Mingce; Brame, Jonathon; Qin, Fan; Bao, Jiming; Li, Qilin; Alvarez, Pedro J J

    2017-01-03

    A major challenge for photocatalytic water purification with TiO 2 is the strong inhibitory effect of natural organic matter (NOM), which can scavenge photogenerated holes and radicals and occlude ROS generation sites upon adsorption. This study shows that phosphate counteracts the inhibitory effect of humic acids (HA) by decreasing HA adsorption and mitigating electron-hole recombination. As a measure of the inhibitory effect of HA, the ratios of first-order reaction rate constants between photocatalytic phenol degradation in the absence versus presence of HA were calculated. This ratio was very high, up to 5.72 at 30 mg/L HA and pH 4.8 without phosphate, but was decreased to 0.76 (5 mg/L HA, pH 8.4) with 2 mM phosphate. The latter ratio indicates a surprising favorable effect of HA on TiO 2 photocatalysis. FTIR analyses suggest that this favorable effect is likely due to a change in the conformation of adsorbed HA, from a multiligand exchange arrangement to a complexation predominantly between COOH groups in HA and the TiO 2 surface in the presence of phosphate. This configuration can reduce hole consumption and facilitate electron transfer to O 2 by the adsorbed HA (indicated by linear sweep voltammetry), which mitigates electron-hole recombination and enhances contaminant degradation. A decrease in HA surface adsorption and hole scavenging (the predominant inhibitory mechanisms of HA) by phosphate (2 mM) was indicated by a 50% decrease in the photocatalytic degradation rate of HA and 80% decrease in the decay rate coefficient of interfacial-related photooxidation in photocurrent transients. These results, which were validated with other compounds (FFA and cimetidine), indicate that anchoring phosphate - or anions that exert similar effects on the TiO 2 surface - might be a feasible strategy to counteract the inhibitory effect of NOM during photocatalytic water treatment.

  6. The dynamics of electron and ion holes in a collisionless plasma

    Directory of Open Access Journals (Sweden)

    B. Eliasson

    2005-01-01

    Full Text Available We present a review of recent analytical and numerical studies of the dynamics of electron and ion holes in a collisionless plasma. The new results are based on the class of analytic solutions which were found by Schamel more than three decades ago, and which here work as initial conditions to numerical simulations of the dynamics of ion and electron holes and their interaction with radiation and the background plasma. Our analytic and numerical studies reveal that ion holes in an electron-ion plasma can trap Langmuir waves, due the local electron density depletion associated with the negative ion hole potential. Since the scale-length of the ion holes are on a relatively small Debye scale, the trapped Langmuir waves are Landau damped. We also find that colliding ion holes accelerate electron streams by the negative ion hole potentials, and that these streams of electrons excite Langmuir waves due to a streaming instability. In our Vlasov simulation of two colliding ion holes, the holes survive the collision and after the collision, the electron distribution becomes flat-topped between the two ion holes due to the ion hole potentials which work as potential barriers for low-energy electrons. Our study of the dynamics between electron holes and the ion background reveals that standing electron holes can be accelerated by the self-created ion cavity owing to the positive electron hole potential. Vlasov simulations show that electron holes are repelled by ion density minima and attracted by ion density maxima. We also present an extension of Schamel's theory to relativistically hot plasmas, where the relativistic mass increase of the accelerated electrons have a dramatic effect on the electron hole, with an increase in the electron hole potential and in the width of the electron hole. A study of the interaction between electromagnetic waves with relativistic electron holes shows that electromagnetic waves can be both linearly and nonlinearly

  7. Attosecond extreme ultraviolet generation in cluster by using spatially inhomogeneous field

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Liqiang, E-mail: lqfeng-lngy@126.com [College of Science, Liaoning University of Technology, Jinzhou, 121000 (China); State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics Chinese Academy of Sciences, Dalian 116023 (China); Liu, Hang [School of Chemical and Environmental Engineering, Liaoning University of Technology, Jinzhou 121000 (China)

    2015-01-15

    A promising method to generate the attosecond extreme ultraviolet (XUV) sources has been theoretically investigated emerging from the two-dimensional Ar{sup +} cluster driven by the spatially inhomogeneous field. The results show that with the introduction of the Ar{sup +} cluster model, not only the harmonic cutoffs are enhanced, but also the harmonic yields are reinforced. Furthermore, by properly moderating the inhomogeneity as well as the laser parameters of the inhomogeneous field, the harmonic cutoff can be further extended. As a result, three almost linearly polarized XUV pulses with durations of 40 as, 42 as, and 45 as can be obtained.

  8. Attosecond control of dissociative ionization of O{sub 2} molecules

    Energy Technology Data Exchange (ETDEWEB)

    Siu, W.; Kelkensberg, F.; Gademann, G. [FOM Institute AMOLF, Science Park 104, NL-1098 XG Amsterdam (Netherlands); Rouzee, A.; Vrakking, M. J. J. [FOM Institute AMOLF, Science Park 104, NL-1098 XG Amsterdam (Netherlands); Max-Born-Institut, Max-Born Strasse 2A, D-12489 Berlin (Germany); Johnsson, P. [FOM Institute AMOLF, Science Park 104, NL-1098 XG Amsterdam (Netherlands); Department of Physics, Lund University, Post Office Box 118, SE-221 00 Lund (Sweden); Dowek, D. [Laboratoire des Collisions Atomiques et Moleculaires (UMR Universite Paris-Sud et CNRS, 8625), Batiment 351, Universite Paris-Sud, F-91405 Orsay Cedex (France); Lucchini, M.; Calegari, F. [Department of Physics, Politecnico di Milano, Istituto di Fotonica e Nanotecnologie CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); De Giovannini, U.; Rubio, A. [Nano-bio Spectroscopy Group, ETSF Scientific Development Centre, Universidad del Pais Vasco, Avenida Tolosa 72, E-20018 San Sebastian (Spain); Lucchese, R. R. [Department of Chemistry, Texas A and M University, Post Office Box 30012, College Station, Texas 77842-3012 (United States); Kono, H. [Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578 (Japan); Lepine, F. [Universite Lyon 1/CNRS/LASIM, UMR 5579, 43 Boulevard Du 11 Novembre 1918, F-69622 Villeurbane (France)

    2011-12-15

    We demonstrate that dissociative ionization of O{sub 2} can be controlled by the relative delay between an attosecond pulse train (APT) and a copropagating infrared (IR) field. Our experiments reveal a dependence of both the branching ratios between a range of electronic states and the fragment angular distributions on the extreme ultraviolet (XUV) to IR time delay. The observations go beyond adiabatic propagation of dissociative wave packets on IR-induced quasistatic potential energy curves and are understood in terms of an IR-induced coupling between electronic states in the molecular ion.

  9. Reemission spectra and inelastic processes at interaction of attosecond and shorter duration electromagnetic pulses with atoms

    International Nuclear Information System (INIS)

    Makarov, D.N.; Matveev, V.I.

    2017-01-01

    Inelastic processes and the reemission of attosecond and shorter electromagnetic pulses by atoms have been considered within the analytical solution of the Schrödinger equation in the sudden perturbation approximation. A method of calculations with the exact inclusion of spatial inhomogeneity of the field of an ultrashort pulse and the momenta of photons in the reemission processes has been developed. The probabilities of inelastic processes and spectra of reemission of ultrashort electromagnetic pulses by one- and many-electron atoms have been calculated. The results have been presented in the form of analytical formulas.

  10. High level harmonic radiation: atto-second impulse generation, application to coherent radiation

    International Nuclear Information System (INIS)

    Kovacev, Milutin

    2003-01-01

    The work presented in this thesis is dedicated to the characterization and optimization of the unique properties of high order harmonic generation in a rare gas: high brilliance, short pulse duration (femtosecond to atto-second, 1 as = 10"-"1"8 s and good mutual coherence. In the first part of this work, we concentrate on the exploitation of a scaling law using a high-energy laser loosely focused inside an extended gaseous medium. For the first time, the generated harmonic energy exceeds the 1 μJ level per laser pulse using the fifteenth harmonic order at a wavelength of 53 nm. The conversion efficiency reaches 4.10"-"5, which results from the combination of a strong dipolar response and a good phase matching within a generating volume that is extended by self guiding of the generating laser pulse. In the second part, our interest is devoted to the temporal profile of the harmonic emission and its atto-second structure. We first demonstrate the feasibility of a spatial/spectral selection of the contributions associated to the two main electronic trajectories, allowing thereby the generation of regular atto-second pulse trains. We then characterize such a pulse train by the measurement of the relative phases of consecutive harmonics. Finally, we describe an original technique for the temporal confinement of the harmonic emission by manipulating the ellipticity of the generating laser beam. In the third part, our interest is dedicated to the mutual coherence properties of the harmonic emission. We first demonstrate the precise control of the relative phase of the harmonic pulses by multiple beam interference in the XUV. This frequency-domain interferometry using four phase-locked temporally separated pulses shows an extreme sensitivity to the relative phase of the pulses on an atto-second time scale. We then measure the first order autocorrelation trace of the harmonic beam thanks to the generation of two harmonic sources mutually coherent and spatially separated

  11. Fractional high-harmonic combs by attosecond-precision split-spectrum pulse control

    Directory of Open Access Journals (Sweden)

    Laux Martin

    2013-03-01

    Full Text Available Few-cycle laser fields enable pulse-shaping control of high-order harmonic generation by time delaying variable broadband spectral sections. We report the experimental generation of fractional (noninteger high-harmonic combs by the controlled interference of two attosecond pulse trains. Additionally the energy of the high harmonics is strongly tuned with the relative time delay. We quantify the tuning to directly result from the controlled variation of the instantaneous laser frequency at the shaped driver pulse intensity maximum.

  12. Phase-resolved attosecond near-threshold photoionization of molecular nitrogen

    International Nuclear Information System (INIS)

    Haessler, S.; Ruchon, T.; Breger, P.; Carre, B.; Salieres, P.; Fabre, B.; Higuet, J.; Constant, E.; Mevel, E.; Mairesse, Y.; Caillat, J.; Maquet, A.; Taieeb, R.

    2009-01-01

    We photoionize nitrogen molecules with a train of extreme ultraviolet attosecond pulses together with a weak infrared field. We measure the phase of the two-color two-photon ionization transition (molecular phase) for different states of the ion. We observe a 0.9π shift for the electrons produced in the ionization channels leading to the X 2 Σ g + , v ' =1, and v ' =2 states. We relate this phase shift to the presence of a complex resonance in the continuum. By providing both a high spectral and temporal resolution, this general approach gives access to the evolution of extremely short-lived states, which is often not accessible otherwise.

  13. A novel optical tool for controlling and probing ultrafast surface dynamics

    International Nuclear Information System (INIS)

    Yang, Yudong

    2017-12-01

    Ultrashort pulse laser sources have been greatly developed over the past few decades. The available pulse duration has been reduced to the single-cycle pulse regime. The discovery of high harmonic generation has freed us from the limitation of the laser wavelength. Moreover, the demonstration of isolated attosecond pulse generation has indicated the advent of the attosecond science era. Attosecond pulses undoubtedly allow one to study ultrafast dynamics with unprecedented time resolution. However, physical systems with genuine attosecond time scale dynamics are rather challenging to find. Ultrafast surface charge transfer, which is an important process in photochemistry and electrochemistry, is a good candidate experimental system exhibiting attosecond electronic dynamics. Specifically, the ultrafast surface charge transfer on the c(4 x 2)S/Ru(0001) surface was previously studied and the charge transfer time inferred to be 320 as using core-hole clock spectroscopy at a synchrotron facility. In order to measure this benchmark attosecond electronic dynamics with real time-resolving methods, pump pulses centered at 160 eV and probe pulses centered at 40 eV are required. To this end, a dedicated attosecond experimental beamline including an ultrashort laser pulse source and an attosecond pulse generation and characterization setup has been designed and is being developed. The author of this thesis was responsible for the construction of the attosecond experimental beamline which will be used ultrafast surface charge transfer studies. In this thesis, a completely functional attosecond extreme ultraviolet (XUV) beamline, which includes a few-cycle laser pulse source, an attosecond pulse generation and characterization setup, is described. A commercial Ti:sapphire-based chirped-pulse amplification (CPA) laser system is the overall source of the beamline. The laser system is actively carrier-envelope phase (CEP) stabilized and the output pulse duration is ∝35 fs. The

  14. A novel optical tool for controlling and probing ultrafast surface dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yudong

    2017-12-15

    Ultrashort pulse laser sources have been greatly developed over the past few decades. The available pulse duration has been reduced to the single-cycle pulse regime. The discovery of high harmonic generation has freed us from the limitation of the laser wavelength. Moreover, the demonstration of isolated attosecond pulse generation has indicated the advent of the attosecond science era. Attosecond pulses undoubtedly allow one to study ultrafast dynamics with unprecedented time resolution. However, physical systems with genuine attosecond time scale dynamics are rather challenging to find. Ultrafast surface charge transfer, which is an important process in photochemistry and electrochemistry, is a good candidate experimental system exhibiting attosecond electronic dynamics. Specifically, the ultrafast surface charge transfer on the c(4 x 2)S/Ru(0001) surface was previously studied and the charge transfer time inferred to be 320 as using core-hole clock spectroscopy at a synchrotron facility. In order to measure this benchmark attosecond electronic dynamics with real time-resolving methods, pump pulses centered at 160 eV and probe pulses centered at 40 eV are required. To this end, a dedicated attosecond experimental beamline including an ultrashort laser pulse source and an attosecond pulse generation and characterization setup has been designed and is being developed. The author of this thesis was responsible for the construction of the attosecond experimental beamline which will be used ultrafast surface charge transfer studies. In this thesis, a completely functional attosecond extreme ultraviolet (XUV) beamline, which includes a few-cycle laser pulse source, an attosecond pulse generation and characterization setup, is described. A commercial Ti:sapphire-based chirped-pulse amplification (CPA) laser system is the overall source of the beamline. The laser system is actively carrier-envelope phase (CEP) stabilized and the output pulse duration is ∝35 fs. The

  15. Attosecond polarization control in atomic RABBITT-like experiments assisted by a circularly polarized laser

    Science.gov (United States)

    Boll, D. I. R.; Fojón, O. A.

    2017-12-01

    We study theoretically the single ionization of noble gas atoms by the combined action of an attosecond pulse train with linear polarization and an assistant laser field with circular polarization. We employ a non-perturbative model that under certain approximations gives closed-form expressions for the angular distributions of photoelectrons. Interestingly, our model allow us to interpret these angular distributions as two-centre interferences where the orientation and the modulus of the separation vector between the virtual emitters is governed by the assistant laser field. Additionally, we show that such a configuration of light fields is similar to the polarization control technique, where both the attosecond pulse train and the assistant laser field have linear polarizations whose relative orientation may be controlled. Moreover, in order to compare our results with the available experimental data, we obtain analytical expressions for the cross sections integrated over the photoelectron emission angles. By means of these expressions, we define the ‘magic time’ as the delay for which the total cross sections for atomic targets exhibit the same functional form as the one of the monochromatic photoionization of diatomic molecular targets.

  16. Plasma effects in attosecond pulse generation from ultra-relativistic laser-plasma interactions

    International Nuclear Information System (INIS)

    Boyd, T.J.M.

    2010-01-01

    Complete text of publication follows. Particle-in-cell simulations were performed to examine the influence of plasma effects on high harmonic spectra from the interaction of ultra-intense p-polarized laser pulses with overdense plasma targets. Furthermore, a theoretical model is proposed to explain the radiation mechanism that leads to attosecond pulse generation in the reflected field. It is shown that plasma harmonic emission affects the spectral characteristics, causing deviations in the harmonic power decay as compared with the so-called universal 8/3-decay. These deviations may occur, in a varying degree, as a consequence of the extent to which the plasma line and its harmonics affect the emission. It is also found a strong correlation of the emitted attosecond pulses with electron density structures within the plasma, responsible to generate intense localised electrostatic fields. A theoretical model based on the excitation of Langmuir waves by the re-entrant Brunel electron beams in the plasma and their electromagnetic interaction with the laser field is proposed to explain the flatter power spectral emission - described by a weaker 5/3 index and observed in numerical simulations - than that of the universal decay.

  17. Angular dependence of the attosecond time delay in the H 2 + ion

    Science.gov (United States)

    Kheifets, Anatoli; Serov, Vladislav

    2016-05-01

    Angular dependence of attosecond time delay relative to polarization of light can now be measured using combination of RABBITT and COLTRIMS techniques. This dependence brings particularly useful information in molecules where it is sensitive to the orientation of the molecular axis. Here we extend the theoretical studies of and consider a molecular ion H2+in combination of an attosecond pulse train and a dressing IR field which is a characteristic set up of a RABBIT measurement. We solve the time-dependent Schrödinger equation using a fast spherical Bessel transformation (SBT) for the radial variable, a discrete variable representation for the angular variables and a split-step technique for the time evolution. The use of SBT ensures correct phase of the wave function for a long time evolution which is especially important in time delay calculations. To speed up computations, we implement an expanding coordinate (EC) system which allows us to reach space sizes and time periods unavailable by other techniques. Australian Research Council DP120101805.

  18. Generation of attosecond electron beams in relativistic ionization by short laser pulses

    Science.gov (United States)

    Cajiao Vélez, F.; Kamiński, J. Z.; Krajewska, K.

    2018-03-01

    Ionization by relativistically intense short laser pulses is studied in the framework of strong-field quantum electrodynamics. Distinctive patterns are found in the energy probability distributions of photoelectrons, which are sensitive to the properties of a driving laser field. It is demonstrated that these electrons are generated in the form of solitary attosecond wave packets. This is particularly important in light of various applications of attosecond electron beams such as in ultrafast electron diffraction and crystallography, or in time-resolved electron microscopy of physical, chemical, and biological processes. We also show that, for intense laser pulses, high-energy ionization takes place in narrow regions surrounding the momentum spiral, the exact form of which is determined by the shape of a driving pulse. The self-intersections of the spiral define the momenta for which the interference patterns in the energy distributions of photoelectrons are observed. Furthermore, these interference regions lead to the synthesis of single-electron wave packets characterized by coherent double-hump structures.

  19. Generation of Attosecond X-Ray Pulse through Coherent Relativistic Nonlinear Thomson Scattering

    CERN Document Server

    Lee, K; Jeong, Y U; Lee, B C; Park, S H

    2005-01-01

    In contrast to some recent experimental results, which state that the Nonlinear Thomson Scattered (NTS) radiation is incoherent, a coherent condition under which the scattered radiation of an incident laser pulse by a bunch of electrons can be coherently superposed has been investigated. The Coherent Relativistic Nonlinear Thomson Scattered (C-RNTS) radiation makes it possible utilizing the ultra-short pulse nature of NTS radiation with a bunch of electrons, such as plasma or electron beams. A numerical simulation shows that a 25 attosecond X-ray pulse can be generated by irradiating an ultra-intense laser pulse of 4x10(19) W/cm2 on an ultra-thin solid target of 50 nm thickness, which is commercially available. The coherent condition can be easily extended to an electron beam from accelerators. Different from the solid target, much narrower electron beam is required for the generation of an attosecond pulse. Instead, this condition could be applied for the generation of intense Compton scattered X-rays with a...

  20. SU-F-T-318: Sensitivity and Stability of OSLDs with Filled Deep Electron/hole Traps Under Pre-Irradiation and Bleaching Conditions

    International Nuclear Information System (INIS)

    Kim, J; Park, S; Lee, H; Kim, H; Choi, C; Park, J

    2016-01-01

    Purpose: This work evaluated the characteristics of optically stimulated luminescence dosimeters (OSLDs) with fully filled deep electron/hole traps (OSLDfull) with the bleaching conditions according to the accumulated dose. Methods: The OSLDs were first pre-irradiated with a Co-60 gamma ray at more than 5 kGy, so as to fill the deep electron and hole traps. Using a 6-MV beam, the OSLDfull characteristics were investigated in terms of the full bleaching, fading, dose linearity, and dose sensitivity obtained in response to the accumulated dose values. To facilitate a comparison of the dose sensitivity, OSLDs with un-filled deep electron/hole traps (OSLDempty) were investigated in the same manner. A long-pass filter was used to exclude bleaching-source wavelengths of less than 520 nm. Various bleaching time and wavelength combinations were used in order to determine the optimal bleaching conditions for the OSLD full. Results: The fading for the OSLDfull exhibited stable signals after 8 min, for both 1- and 10-Gy. For 4-h bleaching time and an unfiltered bleaching device, the supralinear index values for the OSLDfull were 1.003, 1.002, 0.999, and 1.001 for doses of 2, 4, 7, and 10 Gy, respectively. For a 65-Gy accumulated dose with a 5-Gy fraction, no variation in dose sensitivity was obtained for the OSLDfull, within a standard deviation of 0.85%, whereas the OSLDempty dose sensitivity decreased by approximately 2.3% per 10 Gy. The filtered bleaching device yielded a highly stable sensitivity for OSLDfull, independent of bleaching time and within a standard deviation of 0.71%, whereas the OSLDempty dose sensitivity decreased by approximately 4.2% per 10 Gy for an accumulated dose of 25 Gy with a 5-Gy fraction. Conclusion: Under the bleaching conditions determined in this study, clinical dosimetry with OSLDfull is highly stable, having an accuracy of 1% with no change in dose sensitivity or linearity at clinical doses. This work was supported by a National Research

  1. Hybrid graphene and graphitic carbon nitride nanocomposite: gap opening, electron-hole puddle, interfacial charge transfer, and enhanced visible light response.

    Science.gov (United States)

    Du, Aijun; Sanvito, Stefano; Li, Zhen; Wang, Dawei; Jiao, Yan; Liao, Ting; Sun, Qiao; Ng, Yun Hau; Zhu, Zhonghua; Amal, Rose; Smith, Sean C

    2012-03-07

    Opening up a band gap and finding a suitable substrate material are two big challenges for building graphene-based nanodevices. Using state-of-the-art hybrid density functional theory incorporating long-range dispersion corrections, we investigate the interface between optically active graphitic carbon nitride (g-C(3)N(4)) and electronically active graphene. We find an inhomogeneous planar substrate (g-C(3)N(4)) promotes electron-rich and hole-rich regions, i.e., forming a well-defined electron-hole puddle, on the supported graphene layer. The composite displays significant charge transfer from graphene to the g-C(3)N(4) substrate, which alters the electronic properties of both components. In particular, the strong electronic coupling at the graphene/g-C(3)N(4) interface opens a 70 meV gap in g-C(3)N(4)-supported graphene, a feature that can potentially allow overcoming the graphene's band gap hurdle in constructing field effect transistors. Additionally, the 2-D planar structure of g-C(3)N(4) is free of dangling bonds, providing an ideal substrate for graphene to sit on. Furthermore, when compared to a pure g-C(3)N(4) monolayer, the hybrid graphene/g-C(3)N(4) complex displays an enhanced optical absorption in the visible region, a promising feature for novel photovoltaic and photocatalytic applications. © 2012 American Chemical Society

  2. Columnar recombination for X-ray generated electron-holes in amorphous selenium and its significance in a-Se x-ray detectors

    International Nuclear Information System (INIS)

    Bubon, O.; Jandieri, K.; Baranovskii, S. D.; Kasap, S. O.; Reznik, A.

    2016-01-01

    Although amorphous selenium (a-Se) has a long and successful history of application in optical and X-ray imaging, some of its fundamental properties are still puzzling. In particularly, the mechanism of carrier recombination following x-ray excitation and electric field and temperature dependences of the electron-hole pair creation energy (W_e_h_p) remain unclear. Using the combination of X-ray photocurrent and pulse height spectroscopy measurements, we measure W_e_h_p in a wide range of temperatures (218–320 K) and electric fields (10–100 V/µm) and show that the conventional columnar recombination model which assumes Langevin recombination within a column (a primary electron track) fails to explain experimental results in a wide range of electric fields and temperatures. The reason for the failure of the conventional model is revealed in this work, and the theory of the columnar recombination is modified to include the saturation of the recombination rate at high electric field in order to account for the experimental results in the entire range of fields and temperatures.

  3. Attosecond sublevel beating and nonlinear dressing on the 3d-to-5p and 3p-to-5s core-transitions at 91.3 eV and 210.4 eV in krypton.

    Science.gov (United States)

    Seres, Enikoe; Seres, Jozsef; Namba, Shinichi; Afa, John; Serrat, Carles

    2017-12-11

    Applying extreme ultraviolet (XUV) transient absorption spectroscopy, the dynamics of the two laser dressed transitions 3d 5/2 -to-5p 3/2 and 3p 3/2 -to-5s 1/2 at photon energies of 91.3 eV and 210.4 eV were examined with attosecond temporal resolution. The dressing process was modeled with density matrix equations which are found to describe very accurately both the experimentally observed transmission dynamics and the linear and nonlinear dressing oscillations at 0.75 PHz and 1.5 PHz frequencies. Furthermore, using Fourier transform XUV spectroscopy, quantum beats from the 3d 5/2 -3d 3/2 and 3p 3/2 -3p 1/2 sublevels at 0.3 PHz and 2.0 PHz were experimentally identified and resolved.

  4. Measuring the electric field of few-cycle laser pulses by attosecond cross correlation

    International Nuclear Information System (INIS)

    Bandrauk, Andre D.; Chelkowski, Szczepan; Shon, Nguyen Hong

    2002-01-01

    A new technique for directly measuring the electric field of linearly polarized few-cycle laser pulses is proposed. Based on the solution of the time-dependent Schroedinger equation (TDSE) for an H atom in the combined field of infrared (IR) femtosecond (fs) and ultraviolet (UV) attosecond (as) laser pulses we show that, as a function of the time delay between two pulses, the difference (or equivalently, asymmetry) of photoelectron signals in opposite directions (along the polarization vector of laser pulses) reproduces very well the profile of the electric field (or vector potential) in the IR pulse. Such ionization asymmetry can be used for directly measuring the carrier-envelope phase difference (i.e., the relative phase of the carrier frequency with respect to the pulse envelope) of the IR fs laser pulse

  5. Investigation of novel shape-controlled linearly and circularly polarized attosecond pulse sources

    International Nuclear Information System (INIS)

    Tóth, György; Tibai, Zoltán; Nagy-Csiha, Zsuzsanna; Márton, Zsuzsanna; Almási, Gábor; Hebling, János

    2016-01-01

    In this article, we investigate the temporal shape of one- or few-cycle, 20–180 nm central wavelength attosecond pulses that are produced in a scheme based on coherent undulator radiation. It is demonstrated, that the carrier–envelope phase (CEP) of the radiated electric field can be chosen arbitrarily by shaping the magnetic field of the radiator undulator appropriately. It is shown that the temporal shape and the spectrum of the generated electric field are influenced by the spatial shape and amplitude of the magnetic field of the radiator undulator for different central wavelength pulses, while both are practically independent of the energy of the initial electron bunch. Shape distortions at high K undulator parameters are also discussed.

  6. Attosecond Time Delay in Photoionization of Noble-Gas and Halogen Atoms

    Directory of Open Access Journals (Sweden)

    Liang-Wen Pi

    2018-02-01

    Full Text Available Ultrafast processes are now accessible on the attosecond time scale due to the availability of ultrashort XUV laser pulses. Noble-gas and halogen atoms remain important targets due to their giant dipole resonance and Cooper minimum. Here, we calculate photoionization cross section, asymmetry parameter and Wigner time delay using the time-dependent local-density approximation (TDLDA, which includes the electron correlation effects. Our results are consistent with experimental data and other theoretical calculations. The asymmetry parameter provides an extra layer of access to the phase information of the photoionization processes. We find that halogen atoms bear a strong resemblance on cross section, asymmetry parameter and time delay to their noble-gas neighbors. Our predicted time delay should provide a guidance for future experiments on those atoms and related molecules.

  7. Attosecond relative delay among xenon 5p, 5s, and 4d photoionization

    Science.gov (United States)

    Magrakvelidze, Maia; Madjet, Mohamed; Chakraborty, Himadri

    2017-04-01

    Attosecond Wigner-Smith (WS) time delays of the photoemissions of Xe valence 5p, 5s, and core 4d electrons are investigated in details using the time-dependent local density approximation (TDLDA). Electron correlations determine the energy-dependent structures in ionization phases of the dipole channels and in the resulting WS delays at various shape resonances, induced by the collective motion of 4d electrons, and at various Cooper minima. We find that our calculation closely agrees with the streaking measurement for the delay of 4d relative to 5s, and predicts accelerated emission of 5p with respect to 4d as was experimentally observed at similar photon energies for Xe atoms adsorbed on the tungsten surface. This work was supported by the U.S. National Science Foundation.

  8. Robust enhancement of high harmonic generation via attosecond control of ionization.

    Science.gov (United States)

    Bruner, Barry D; Krüger, Michael; Pedatzur, Oren; Orenstein, Gal; Azoury, Doron; Dudovich, Nirit

    2018-04-02

    High-harmonic generation (HHG) is a powerful tool to generate coherent attosecond light pulses in the extreme ultraviolet. However, the low conversion efficiency of HHG at the single atom level poses a significant practical limitation for many applications. Enhancing the efficiency of the process defines one of the primary challenges in the application of HHG as an advanced XUV source. In this work, we demonstrate a new mechanism, which in contrast to current methods, enhances the HHG conversion efficiency purely on a single particle level. We show that using a bichromatic driving field, sub-optical-cycle control and enhancement of the tunnelling ionization rate can be achieved, leading to enhancements in HHG efficiency by up to two orders of magnitude. Our method advances the perspectives of HHG spectroscopy, where isolating the single particle response is an essential component, and offers a simple route toward scalable, robust XUV sources.

  9. Attosecond nanotechnology: NEMS of energy storage and nanostructural transformations in materials

    Energy Technology Data Exchange (ETDEWEB)

    Beznosyuk, Sergey A., E-mail: bsa1953@mail.ru; Maslova, Olga A., E-mail: maslova-o.a@mail.ru [Altai State University, Barnaul, 656049 (Russian Federation); Zhukovsky, Mark S., E-mail: zhukovsky@list.ru [Altai State Technical University, Barnaul, 656038 (Russian Federation)

    2015-10-27

    The attosecond technology of the nanoelectromechanical system (NEMS) energy storage as active center fast transformation of nanostructures in materials is considered. The self-organizing relaxation of the NEMS active center containing nanocube of 256-atoms limited by planes (100) in the FCC lattice matrix of 4d-transition metals (Ru, Rh, Pd) is described by the quantum NEMS-kinetics (NK) method. Typical for these metals change of the NEMS active center physicochemical characteristics during the time of relaxation is presented. There are three types of intermediate quasistationary states of the NEMS active center. Their forms are plainly distinguishable. The full relaxed NEMS active centers (Ru{sub 256}, Rh{sub 256}, Pd{sub 256}) accumulate next storage energies: E{sub Ru} = 2.27 eV/at, E{sub Rh} = 1.67 eV/at, E{sub Pd} = 3.02 eV/at.

  10. Generation of a strong attosecond pulse train with an orthogonally polarized two-color laser field

    International Nuclear Information System (INIS)

    Kim, Chul Min; Kim, I Jong; Nam, Chang Hee

    2005-01-01

    We theoretically investigate the high-order harmonic generation from a neon atom irradiated by an intense two-color femtosecond laser pulse, in which the fundamental field and its second harmonic are linearly polarized and orthogonal to each other. In contrast to usual high-harmonic generation with linearly polarized fundamental field alone, a very strong and clean high-harmonic spectrum, consisting of both odd and even orders of harmonics, can be generated in the orthogonally polarized two-color laser field with proper selection of the relative phase between the fundamental and second-harmonic fields. In time domain, this results in a strong and regular attosecond pulse train. The origin of these behaviors is elucidated by analyzing semiclassical electron paths and by simulating high-harmonic generation quantum mechanically

  11. Investigation of novel shape-controlled linearly and circularly polarized attosecond pulse sources

    Energy Technology Data Exchange (ETDEWEB)

    Tóth, György [MTA-PTE High-Field Terahertz Research Group, 7624 Pécs (Hungary); Tibai, Zoltán; Nagy-Csiha, Zsuzsanna [Institute of Physics, University of Pécs, 7624 Pécs (Hungary); Márton, Zsuzsanna [MTA-PTE High-Field Terahertz Research Group, 7624 Pécs (Hungary); Institute of Physics, University of Pécs, 7624 Pécs (Hungary); Almási, Gábor; Hebling, János [MTA-PTE High-Field Terahertz Research Group, 7624 Pécs (Hungary); Institute of Physics, University of Pécs, 7624 Pécs (Hungary); Szentágothai Research Centre, 7624 Pécs (Hungary)

    2016-02-15

    In this article, we investigate the temporal shape of one- or few-cycle, 20–180 nm central wavelength attosecond pulses that are produced in a scheme based on coherent undulator radiation. It is demonstrated, that the carrier–envelope phase (CEP) of the radiated electric field can be chosen arbitrarily by shaping the magnetic field of the radiator undulator appropriately. It is shown that the temporal shape and the spectrum of the generated electric field are influenced by the spatial shape and amplitude of the magnetic field of the radiator undulator for different central wavelength pulses, while both are practically independent of the energy of the initial electron bunch. Shape distortions at high K undulator parameters are also discussed.

  12. Direct View of Hot Carrier Dynamics in Graphene

    DEFF Research Database (Denmark)

    Johannsen, Jens Christian; Ulstrup, Søren; Cilento, Federico

    2013-01-01

    The ultrafast dynamics of excited carriers in graphene is closely linked to the Dirac spectrum and plays a central role for many electronic and optoelectronic applications. Harvesting energy from excited electron-hole pairs, for instance, is only possible if these pairs can be separated before th...

  13. Double carriers pulse DLTS for the characterization of electron-hole recombination process in GaAsN grown by chemical beam epitaxy

    International Nuclear Information System (INIS)

    Bouzazi, Boussairi; Suzuki, Hidetoshi; Kojima, Nobuaki; Ohshita, Yoshio; Yamaguchi, Masafumi

    2011-01-01

    A nitrogen-related electron trap (E1), located approximately 0.33 eV from the conduction band minimum of GaAsN grown by chemical beam epitaxy, was confirmed by investigating the dependence of its density with N concentration. This level exhibits a high capture cross section compared with that of native defects in GaAs. Its density increases significantly with N concentration, persists following post-thermal annealing, and was found to be quasi-uniformly distributed. These results indicate that E1 is a stable defect that is formed during growth to compensate for the tensile strain caused by N. Furthermore, E1 was confirmed to act as a recombination center by comparing its activation energy with that of the recombination current in the depletion region of the alloy. However, this technique cannot characterize the electron-hole (e-h) recombination process. For that, double carrier pulse deep level transient spectroscopy is used to confirm the non-radiative e-h recombination process through E1, to estimate the capture cross section of holes, and to evaluate the energy of multi-phonon emission. Furthermore, a configuration coordinate diagram is modeled based on the physical parameters of E1. -- Research Highlights: → Double carrier pulse DLTS method confirms the existence of SRH center. → The recombination center in GaAsN depends on nitrogen concentration. → Minority carrier lifetime in GaAsN is less than 1 ns. → A non-radiative recombination center exits in GaAsN.

  14. Atomistic Tight-Binding Theory of Electron-Hole Exchange Interaction in Morphological Evolution of CdSe/ZnS Core/Shell Nanodisk to CdSe/ZnS Core/Shell Nanorod

    Directory of Open Access Journals (Sweden)

    Worasak Sukkabot

    2016-01-01

    Full Text Available Based on the atomistic tight-binding theory (TB and a configuration interaction (CI description, the electron-hole exchange interaction in the morphological transformation of CdSe/ZnS core/shell nanodisk to CdSe/ZnS core/shell nanorod is described with the aim of understanding the impact of the structural shapes on the change of the electron-hole exchange interaction. Normally, the ground hole states confined in typical CdSe/ZnS core/shell nanocrystals are of heavy hole-like character. However, the atomistic tight-binding theory shows that a transition of the ground hole states from heavy hole-like to light hole-like contribution with the increasing aspect ratios of the CdSe/ZnS core/shell nanostructures is recognized. According to the change in the ground-state hole characters, the electron-hole exchange interaction is also significantly altered. To do so, optical band gaps, ground-state electron character, ground-state hole character, oscillation strengths, ground-state coulomb energies, ground-state exchange energies, and dark-bright (DB excitonic splitting (stoke shift are numerically demonstrated. These atomistic computations obviously show the sensitivity with the aspect ratios. Finally, the alteration in the hole character has a prominent effect on dark-bright (DB excitonic splitting.

  15. Self-referencing, spectrally, or spatially encoded spectral interferometry for the complete characterization of attosecond electromagnetic pulses

    International Nuclear Information System (INIS)

    Cormier, Eric; Walmsley, Ian A.; Wyatt, Adam S.; Corner, Laura; Kosik, Ellen M.; DiMauro, Louis F.

    2005-01-01

    We propose a method for the complete characterization of attosecond duration electromagnetic pulses produced by high harmonic generation in an atomic gas. Our method is based on self-referencing spectral interferometry of two spectrally sheared extreme ultraviolet pulses, which is achieved by pumping the harmonic source with two sheared optical driving pulses. The resulting interferogram contains sufficient information to completely reconstruct the temporal behavior of the electric field. We demonstrate that such a method is feasible, and outline two possible experimental configurations

  16. High-order harmonic generation spectra and isolated attosecond pulse generation with a two-color time delayed pulse

    International Nuclear Information System (INIS)

    Feng Liqiang; Chu Tianshu

    2012-01-01

    Highlights: ► Investigation of HHG spectra and single isolated attosecond pulse generation. ► Irradiation from a model Ne atom by two-color time delayed pulse. ► Observation of time delay effect and relative phase effect. ► Revelation of the optimal condition for generating isolated attosecond pulse. ► Generation of a single isolated attosecond pulse of 45as. - Abstract: In this paper, we theoretically investigate the delay time effect on the high-order harmonic generation (HHG) when a model Ne atom is exposed to a two-color time delayed pulse, consisting of a 5fs/800 nm fundamental field and a 20fs/2000 nm controlling field. It shows that the HHG spectra are strongly sensitive to the delay time between the two laser fields, in particular, for the zero carrier-envelope phase (CEP) φ case (corresponding to the 800 nm fundamental field), the maximum cutoff energy has been achieved at zero delay time. However, with the introduction of the CEP (φ = 180°), the delay effect on HHG is changed, exhibiting a ‘U’ structure harmonic emission from −1 T to 1 T. In addition, the combinations of different controlling pulse frequencies and pulse intensities have also been considered, showing the similar results as the original controlling field case, but with some characteristics. Finally, by properly superposing the optimal harmonic spectrum, an isolated 45as pulse is generated without phase compensation.

  17. Quantum dynamic imaging theoretical and numerical methods

    CERN Document Server

    Ivanov, Misha

    2011-01-01

    Studying and using light or "photons" to image and then to control and transmit molecular information is among the most challenging and significant research fields to emerge in recent years. One of the fastest growing areas involves research in the temporal imaging of quantum phenomena, ranging from molecular dynamics in the femto (10-15s) time regime for atomic motion to the atto (10-18s) time scale of electron motion. In fact, the attosecond "revolution" is now recognized as one of the most important recent breakthroughs and innovations in the science of the 21st century. A major participant in the development of ultrafast femto and attosecond temporal imaging of molecular quantum phenomena has been theory and numerical simulation of the nonlinear, non-perturbative response of atoms and molecules to ultrashort laser pulses. Therefore, imaging quantum dynamics is a new frontier of science requiring advanced mathematical approaches for analyzing and solving spatial and temporal multidimensional partial differ...

  18. Dynamics of the phase transitions in the system of nonequilibrium charge carriers in quantum-dimensional Si{sub 1−x}Ge{sub x}/Si structures

    Energy Technology Data Exchange (ETDEWEB)

    Bagaev, V. S.; Krivobok, V. S., E-mail: krivobok@lebedev.ru; Nikolaev, S. N.; Onishchenko, E. E.; Pruchkina, A. A.; Aminev, D. F.; Skorikov, M. L. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Lobanov, D. N.; Novikov, A. V. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)

    2013-11-15

    The dynamics of the phase transition from an electron-hole plasma to an exciton gas is studied during pulsed excitation of heterostructures with Si{sub 1−x}Ge{sub x}/Si quantum wells. The scenario of the phase transition is shown to depend radically on the germanium content in the Si{sub 1−x}Ge{sub x} layer. The electron-hole system decomposes into a rarefied exciton and a dense plasma phases for quantum wells with a germanium content x = 3.5% in the time range 100–500 ns after an excitation pulse. In this case, the electron-hole plasma existing in quantum wells has all signs of an electron-hole liquid. A qualitatively different picture of the phase transition is observed for quantum wells with x = 9.5%, where no separation into phases with different electronic spectra is detected. The carrier recombination in the electron-hole plasma leads a gradual weakening of screening and the appearance of exciton states. For a germanium content of 5–7%, the scenario of the phase transition is complex: 20–250 ns after an excitation pulse, the properties of the electron-hole system are described in terms of a homogeneous electron-hole plasma, whereas its separation into an electron-hole liquid and an exciton gas is detected after 350 ns. It is shown that, for the electron-hole liquid to exist in quantum wells with x = 5–7% Ge, the exciton gas should have a substantially higher density than in quantum wells with x = 3.5% Ge. This finding agrees with a decrease in the depth of the local minimum of the electron-hole plasma energy with increasing germanium concentration in the SiGe layer. An increase in the density of the exciton gas coexisting with the electron-hole liquid is shown to enhance the role of multiparticle states, which are likely to be represented by trions T{sup +} and biexcitons, in the exciton gas.

  19. Attosecond pulse generation in noble gases in the presence of extreme high intensity THz pulses

    International Nuclear Information System (INIS)

    Balogh, E.; Varju, K.

    2010-01-01

    Complete text of publication follows. The shortest - attosecond - light pulses available today are produced by high harmonic generation (HHG) of near-infrared (NIR) laser pulses in noble gas jets, providing a broad spectral plateau of XUV radiation ending in a cutoff. The minimum pulse duration is determined by the achievable bandwidth (i.e. the position of the cutoff), and the chirp of the produced pulses. The extension of the cutoff by increasing the laser intensity is limited by the depletion and phase matching problems of the medium. An alternative method demonstrated to produce higher harmonic orders is by using longer pump pulse wavelength, with the disadvantage of decreased efficiency. Recently it was shown that application of a quasi-DC high strength electric field results in an increase of more than a factor of two in the order of efficiently generated high harmonics. However, the possibility to implement the method proposed in [3] of using a CO 2 laser to create a quasi-DC field for assisting HHG of the NIR laser is questionable, because it's technically very challenging to synchronize pulses from different laser sources. Alternatively, synchronous production of THz pulses with the NIR laser pulse offers a more promising route. The first numerical test of this idea has been reported in [4]. In this contribution we further investigate the method for realistic THz field strengths and short driving pulses, exploring the effect of longer pump laser wavelength on the process. We assume the presence of high intensity THz pulses for supplying the high-strength quasi-DC electric field. The spectrum as well as the chirp of the produced radiation is calculated. We use the non-adiabatic saddle point method to determine the generated radiation described in [6]. We simulate harmonic generation in noble gas atoms, with few cycle NIR pulses of peak intensity at and above 2 x 10 14 W/cm 2 (388 MV/cm) and wavelengths 800 nm and 1560 nm. The THz field strength is varied

  20. Self-probing spectroscopy of XUV photo-ionization dynamics in atoms subjected to a strong-field environment.

    Science.gov (United States)

    Azoury, Doron; Krüger, Michael; Orenstein, Gal; Larsson, Henrik R; Bauch, Sebastian; Bruner, Barry D; Dudovich, Nirit

    2017-11-13

    Single-photon ionization is one of the most fundamental light matter interactions in nature, serving as a universal probe of the quantum state of matter. By probing the emitted electron, one can decode the full dynamics of the interaction. When photo-ionization is evolving in the presence of a strong laser field, the fundamental properties of the mechanism can be signicantly altered. Here we demonstrate how the liberated electron can perform a self-probing measurement of such interaction with attosecond precision. Extreme ultraviolet attosecond pulses initiate an electron wavepacket by photo-ionization, a strong infrared field controls its motion, and finally electron-ion collision maps it into re-emission of attosecond radiation bursts. Our measurements resolve the internal clock provided by the self-probing mechanism, obtaining a direct insight into the build-up of photo-ionization in the presence of the strong laser field.

  1. Energy-resolved attosecond interferometric photoemission from Ag(111) and Au(111) surfaces

    Science.gov (United States)

    Ambrosio, M. J.; Thumm, U.

    2018-04-01

    Photoelectron emission from solid surfaces induced by attosecond pulse trains into the electric field of delayed phase-coherent infrared (IR) pulses allows the surface-specific observation of energy-resolved electronic phase accumulations and photoemission delays. We quantum-mechanically modeled interferometric photoemission spectra from the (111) surfaces of Au and Ag, including background contributions from secondary electrons and direct emission by the IR pulse, and adjusted parameters of our model to energy-resolved photoelectron spectra recently measured at a synchrotron light source by Roth et al. [J. Electron Spectrosc. 224, 84 (2018), 10.1016/j.elspec.2017.05.008]. Our calculated spectra and photoelectron phase shifts are in fair agreement with the experimental data of Locher et al. [Optica 2, 405 (2015), 10.1364/OPTICA.2.000405]. Our model's not reproducing the measured energy-dependent oscillations of the Ag(111) photoemission phases may be interpreted as evidence for subtle band-structure effects on the final-state photoelectron-surface interaction not accounted for in our simulation.

  2. Breaking the Attosecond, Angstrom and TV/m Field Barriers with Ultrafast Electron Beams

    International Nuclear Information System (INIS)

    Rosenzweig, J. B.; Andonian, G.; Fukasawa, A.; Hemsing, E.; Marcus, G.; Marinelli, A.; Musumeci, P.; O'Shea, B.; O'Shea, F.; Pellegrini, C.; Schiller, D.; Travish, G.; Bucksbaum, P.; Hogan, M.; Krejcik, Patrick; Ferrario, M.; Muggli, Patric

    2010-01-01

    Recent initiatives at UCLA concerning ultra-short, GeV electron beam generation have been aimed at achieving sub-fs pulses capable of driving X-ray free-electron lasers (FELs) in single-spike mode. This scheme uses very low charge beams, which may allow existing FEL injectors to produce few-100 attosecond pulses, with very high brightness. Towards this end, recent experiments at the Stanford X-ray FEL (LCLS, first of its kind, built with essential UCLA leadership) have produced ∼2 fs, 20 pC electron pulses. We discuss here extensions of this work, in which we seek to exploit the beam brightness in FELs, in tandem with new developments at UCLA in cryogenic undulator technology, to create compact accelerator/undulator systems that can lase below 0.15 Angst , or be used to permit 1.5 Angst operation at 4.5 GeV. In addition, we are now developing experiments which use the present LCLS fs pulses to excite plasma wakefields exceeding 1 TV/m, permitting a table-top TeV accelerator for frontier high energy physics applications. We discuss the experimental issues associated with this initiative.

  3. Relativistic attosecond electron bunch emission from few-cycle laser irradiated nanoscale droplets

    Directory of Open Access Journals (Sweden)

    Laura Di Lucchio

    2015-02-01

    Full Text Available Attosecond electron bunches produced at the surface of nanometer-scale droplets illuminated by a two-cycle laser pulse are investigated for the purpose of determining their optimal emission characteristics. Significant departures from Mie theory are found for electron bunch emission from droplets whose radii satisfy the condition δ_{r}

  4. Attosecond-controlled photoemission from metal nanowire tips in the few-electron regime

    KAUST Repository

    Ahn, B.

    2017-02-07

    Metal nanotip photoemitters have proven to be versatile in fundamental nanoplasmonics research and applications, including, e.g., the generation of ultrafast electron pulses, the adiabatic focusing of plasmons, and as light-triggered electron sources for microscopy. Here, we report the generation of high energy photoelectrons (up to 160 eV) in photoemission from single-crystalline nanowire tips in few-cycle, 750-nm laser fields at peak intensities of (2-7.3) × 1012 W/cm2. Recording the carrier-envelope phase (CEP)-dependent photoemission from the nanowire tips allows us to identify rescattering contributions and also permits us to determine the high-energy cutoff of the electron spectra as a function of laser intensity. So far these types of experiments from metal nanotips have been limited to an emission regime with less than one electron per pulse. We detect up to 13 e/shot and given the limited detection efficiency, we expect up to a few ten times more electrons being emitted from the nanowire. Within the investigated intensity range, we find linear scaling of cutoff energies. The nonlinear scaling of electron count rates is consistent with tunneling photoemission occurring in the absence of significant charge interaction. The high electron energy gain is attributed to field-induced rescattering in the enhanced nanolocalized fields at the wires apex, where a strong CEP-modulation is indicative of the attosecond control of photoemission.

  5. Molecular electron recollision dynamics in intense circularly polarized laser pulses

    Science.gov (United States)

    Bandrauk, André D.; Yuan, Kai-Jun

    2018-04-01

    Extreme UV and x-ray table top light sources based on high-order harmonic generation (HHG) are focused now on circular polarization for the generation of circularly polarized attosecond pulses as new tools for controlling electron dynamics, such as charge transfer and migration and the generation of attosecond quantum electron currents for ultrafast magneto-optics. A fundamental electron dynamical process in HHG is laser induced electron recollision with the parent ion, well established theoretically and experimentally for linear polarization. We discuss molecular electron recollision dynamics in circular polarization by theoretical analysis and numerical simulation. The control of the polarization of HHG with circularly polarized ionizing pulses is examined and it is shown that bichromatic circularly polarized pulses enhance recollision dynamics, rendering HHG more efficient, especially in molecules because of their nonspherical symmetry. The polarization of the harmonics is found to be dependent on the compatibility of the rotational symmetry of the net electric field created by combinations of bichromatic circularly polarized pulses with the dynamical symmetry of molecules. We show how the field and molecule symmetry influences the electron recollision trajectories by a time-frequency analysis of harmonics. The results, in principle, offer new unique controllable tools in the study of attosecond molecular electron dynamics.

  6. Disappearance of electron-hole asymmetry in nanoparticles of Nd1−xCaxMnO3(x=0.6,0.4): magnetization and electron paramagnetic resonance evidence

    International Nuclear Information System (INIS)

    Bhagyashree, K. S.; Bhat, S. V.

    2015-01-01

    We study and compare magnetic and electron paramagnetic resonance behaviors of bulk and nanoparticles of Nd 1−x Ca x MnO 3 in hole doped (x=0.4;NCMOH) and electron doped (x=0.6;NCMOE) samples. NCMOH in bulk form shows a complex temperature dependence of magnetization M(T), with a charge ordering transition at ∼250 K, an antiferromagnetic (AFM) transition at ∼150 K, and a transition to a canted AFM phase/mixed phase at ∼80 K. Bulk NCMOE behaves quite differently with just a charge ordering transition at ∼280 K, thus providing a striking example of the so called electron-hole asymmetry. While our magnetization data on bulk samples are consistent with the earlier reports, the new results on the nanoparticles bring out drastic effects of size reduction. They show that M(T) behaviors of the two nanosamples are essentially similar in addition to the absence of the charge order in them thus providing strong evidence for vanishing of the electron-hole asymmetry in nanomanganites. This conclusion is further corroborated by electron paramagnetic resonance studies which show that the large difference in the “g” values and their temperature dependences found for the two bulk samples disappears as they approach a common behavior in the corresponding nanosamples

  7. Single attosecond pulse generation in an orthogonally polarized two-color laser field combined with a static electric field

    International Nuclear Information System (INIS)

    Xia Changlong; Zhang Gangtai; Wu Jie; Liu Xueshen

    2010-01-01

    We investigate theoretic high-order harmonic generation and single attosecond pulse generation in an orthogonally polarized two-color laser field, which is synthesized by a mid-infrared (IR) pulse (12.5 fs, 2000 nm) in the y component and a much weaker (12 fs, 800 nm) pulse in the x component. We find that the width of the harmonic plateau can be extended when a static electric field is added in the y component. We also investigate emission time of harmonics in terms of a time-frequency analysis to illustrate the physical mechanism of high-order harmonic generation. We calculate the ionization rate using the Ammosov-Delone-Krainov model and interpret the variation of harmonic intensity for different static electric field strengths. When the ratio of strengths of the static and the y-component laser fields is 0.1, a continuous harmonic spectrum is formed from 220 to 420 eV. By superposing a properly selected range of the harmonic spectrum from 300 to 350 eV, an isolated attosecond pulse with a duration of about 75 as is obtained, which is near linearly polarized.

  8. Coherent dynamics of plasma mirrors

    Energy Technology Data Exchange (ETDEWEB)

    Thaury, C; George, H; Quere, F; Monot, P; Martin, Ph [CEA, DSM, IRAMIS, Serv Photons Atomes and Mol, F-91191 Gif Sur Yvette, (France); Loch, R [Univ Twente, Laser Phys and Nonlinear Opt Grp, Fac Sci and Technol, MESA Inst Nanotechnol, NL-7500 AE Enschede, (Netherlands); Geindre, J P [Ecole Polytech, Lab Pour Utilisat Lasers Intenses, CNRS, F-91128 Palaiseau, (France)

    2008-07-01

    Coherent ultrashort X-ray pulses provide new ways to probe matter and its ultrafast dynamics. One of the promising paths to generate these pulses consists of using a nonlinear interaction with a system to strongly and periodically distort the waveform of intense laser fields, and thus produce high-order harmonics. Such distortions have so far been induced by using the nonlinear polarizability of atoms, leading to the production of atto-second light bursts, short enough to study the dynamics of electrons in matter. Shorter and more intense atto-second pulses, together with higher harmonic orders, are expected by reflecting ultra intense laser pulses on a plasma mirror - a dense (approximate to 10{sup 23} electrons cm{sup -3}) plasma with a steep interface. However, short-wavelength-light sources produced by such plasmas are known to generally be incoherent. In contrast, we demonstrate that like in usual low-intensity reflection, the coherence of the light wave is preserved during harmonic generation on plasma mirrors. We then exploit this coherence for interferometric measurements and thus carry out a first study of the laser-driven coherent dynamics of the plasma electrons. (authors)

  9. Mathematical modeling of the infrastructure of attosecond actuators and femtosecond sensors of nonequilibrium physical media in smart materials

    Science.gov (United States)

    Beznosyuk, Sergey A.; Maslova, Olga A.; Zhukovsky, Mark S.; Valeryeva, Ekaterina V.; Terentyeva, Yulia V.

    2017-12-01

    The task of modeling the multiscale infrastructure of quantum attosecond actuators and femtosecond sensors of nonequilibrium physical media in smart materials is considered. Computer design and calculation of supra-atomic femtosecond sensors of nonequilibrium physical media in materials based on layered graphene-transition metal nanosystems are carried out by vdW-DF and B3LYP methods. It is shown that the molybdenum substrate provides fixation of graphene nanosheets by Van der Waals forces at a considerable distance (5.3 Å) from the metal surface. This minimizes the effect of the electronic and nuclear subsystem of the substrate metal on the sensory properties of "pure" graphene. The conclusion is substantiated that graphene-molybdenum nanosensors are able to accurately orient and position one molecule of carbon monoxide. It is shown that graphene selectively adsorbs CO and fixes the oxygen atom of the molecule at the position of the center of the graphene ring C6.

  10. High-order harmonic and attosecond pulse generation for a few-cycle laser pulse in modulated hollow fibres

    International Nuclear Information System (INIS)

    Zhang Xiangyun; Sun Zhenrong; Wang Yufeng; Chen Guoliang; Wang Zugeng; Li Ruxin; Zeng Zhinan; Xu Zhizhan

    2007-01-01

    High harmonic generation from Ar and He atoms by a few-cycle laser pulse in periodic and chirped hollow fibres is investigated theoretically by a self-consistent model. Based on enhanced high harmonics in a periodic hollow fibre, a chirped hollow fibre is proposed to improve quasi-phase matching for the generated harmonics near the cutoff. The results show that the extended and enhanced harmonics near the cutoff are well phase-matched, and a single x-ray pulse with a duration of 279 as in Ar gas and 255 as in He gas can be achieved by frequency synthesizing of high harmonics in the well-selected cutoff bandwidth. The results show that this technique is a potential candidate to generate an intense isolated attosecond pulse in the 'water window' spectrum

  11. Coherent dynamics in semiconductors

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher

    1998-01-01

    enhanced in quantum confined lower-dimensional systems, where exciton and biexciton effects dominate the spectra even at room temperature. The coherent dynamics of excitons are at modest densities well described by the optical Bloch equations and a number of the dynamical effects known from atomic......Ultrafast nonlinear optical spectroscopy is used to study the coherent dynamics of optically excited electron-hole pairs in semiconductors. Coulomb interaction implies that the optical inter-band transitions are dominated, at least at low temperatures, by excitonic effects. They are further...... and molecular systems are found and studied in the exciton-biexciton system of semiconductors. At densities where strong exciton interactions, or many-body effects, become dominant, the semiconductor Bloch equations present a more rigorous treatment of the phenomena Ultrafast degenerate four-wave mixing is used...

  12. Control of quantum paths of high-order harmonics and attosecond pulse generation in the presence of a static electric field

    International Nuclear Information System (INIS)

    Hong Weiyi; Lu Peixiang; Cao Wei; Lan Pengfei; Wang Xinlin

    2007-01-01

    The time-frequency properties of high-order harmonic generation in the presence of a static electric field are investigated. It is found that the quantum paths contributing to the harmonics can be controlled by adding a static electric field. The highest photon energies of harmonics emitted in the adjacent half-cycles of the laser field are modulated by the static electric field, and then an attosecond pulse train with one burst per optical cycle can be extracted. For the ratio between the laser and the static field of 0.39, the harmonic spectrum is extended to I p + 9.1U p , and the harmonics above I p + 0.7U p are emitted almost in phase. The phase-locked harmonics covered by a broad bandwidth are produced, and then a regular attosecond pulse train with a pulse duration of 80 as is generated

  13. Helicity-Selective Phase-Matching and Quasi-Phase matching of Circularly Polarized High-Order Harmonics: Towards Chiral Attosecond Pulses

    Science.gov (United States)

    2016-05-23

    2 Department of Physics and JILA, University of Colorado and NIST, Boulder, CO 80309, USA 3Department of Physics and Optical Engineering, Ort Braude...polarized high harmonic generation, phase matching, ultrafast chiral physics, attosecond pulses (Some figures may appear in colour only in the online...temporal resolution and in spectral regions unavailable to circular polarization thus far. Acknowledgments This work was supported by the USA –Israel

  14. Dynamics of valence-shell electrons and nuclei probed by strong-field holography and rescattering

    Science.gov (United States)

    Walt, Samuel G.; Bhargava Ram, Niraghatam; Atala, Marcos; Shvetsov-Shilovski, Nikolay I; von Conta, Aaron; Baykusheva, Denitsa; Lein, Manfred; Wörner, Hans Jakob

    2017-01-01

    Strong-field photoelectron holography and laser-induced electron diffraction (LIED) are two powerful emerging methods for probing the ultrafast dynamics of molecules. However, both of them have remained restricted to static systems and to nuclear dynamics induced by strong-field ionization. Here we extend these promising methods to image purely electronic valence-shell dynamics in molecules using photoelectron holography. In the same experiment, we use LIED and photoelectron holography simultaneously, to observe coupled electronic-rotational dynamics taking place on similar timescales. These results offer perspectives for imaging ultrafast dynamics of molecules on femtosecond to attosecond timescales. PMID:28643771

  15. Dynamics at Solid State Surfaces and Interfaces, Volume 1 Current Developments

    CERN Document Server

    Bovensiepen, Uwe; Wolf, Martin

    2010-01-01

    This two-volume work covers ultrafast structural and electronic dynamics of elementary processes at solid surfaces and interfaces, presenting the current status of photoinduced processes. Providing valuable introductory information for newcomers to this booming field of research, it investigates concepts and experiments, femtosecond and attosecond time-resolved methods, as well as frequency domain techniques. The whole is rounded off by a look at future developments.

  16. On the fly quantum dynamics of electronic and nuclear wave packets

    Science.gov (United States)

    Komarova, Ksenia G.; Remacle, F.; Levine, R. D.

    2018-05-01

    Multielectronic states quantum dynamics on a grid is described in a manner motivated by on the fly classical trajectory computations. Non stationary electronic states are prepared by a few cycle laser pulse. The nuclei respond and begin moving. We solve the time dependent Schrödinger equation for the electronic and nuclear dynamics for excitation from the ground electronic state. A satisfactory accuracy is possible using a localized description on a discrete grid. This enables computing on the fly for both the nuclear and electronic dynamics including non-adiabatic couplings. Attosecond dynamics in LiH is used as an example.

  17. Single attosecond pulse generation by using plasmon-driven double optical gating technology in crossed metal nanostructures

    Science.gov (United States)

    Feng, Liqiang; Liu, Katheryn

    2018-05-01

    An effective method to obtain the single attosecond pulses (SAPs) by using the multi-cycle plasmon-driven double optical gating (DOG) technology in the specifically designed metal nanostructures has been proposed and investigated. It is found that with the introduction of the crossed metal nanostructures along the driven and the gating polarization directions, not only the harmonic cutoff can be extended, but also the efficient high-order harmonic generation (HHG) at the very highest orders occurs only at one side of the region inside the nanostructure. As a result, a 93 eV supercontinuum with the near stable phase can be found. Further, by properly introducing an ultraviolet (UV) pulse into the driven laser polarization direction (which is defined as the DOG), the harmonic yield can be enhanced by two orders of magnitude in comparison with the singe polarization gating (PG) technology. However, as the polarized angle or the ellipticity of the UV pulse increase, the enhancement of the harmonic yield is slightly reduced. Finally, by superposing the selected harmonics from the DOG scheme, a 30 as SAP with intensity enhancement of two orders of magnitude can be obtained.

  18. Enhanced asymmetry in few-cycle attosecond pulse ionization of He in the vicinity of autoionizing resonances

    International Nuclear Information System (INIS)

    Djiokap, J M Ngoko; Starace, Anthony F; Hu, S X; Jiang Weichao; Peng Liangyou

    2012-01-01

    By solving the two-active-electron, time-dependent Schrödinger equation in its full dimensionality, we investigate the carrier-envelope phase (CEP) dependence of single ionization of He to the He + (1s) state triggered by an intense few-cycle attosecond pulse with carrier frequency ω corresponding to the energy ℏω = 36 eV. Effects of electron correlations are probed by comparing projections of the final state of the two-electron wave packet onto field-free highly correlated Jacobi matrix wave functions with projections onto uncorrelated Coulomb wave functions. Significant differences are found in the vicinity of autoionizing resonances. Owing to the broad bandwidths of our 115 and 230 as pulses and their high intensities (1–2 PW cm −2 ), asymmetries are found in the differential probability for ionization of electrons parallel and antiparallel to the linear polarization axis of the laser pulse. These asymmetries stem from interference of the one- and two-photon ionization amplitudes for producing electrons with the same momentum along the linear polarization axis. Whereas these asymmetries generally decrease with increasing ionized electron kinetic energy, we find a large enhancement of the asymmetry in the vicinity of two-electron doubly excited (autoionizing) states on an energy scale comparable to the widths of the autoionizing states. The CEP dependence of the energy-integrated asymmetry agrees very well with the predictions of time-dependent perturbation theory (Pronin et al 2009 Phys. Rev. A 80 063403). (paper)

  19. Solvothermal syntheses of Bi and Zn co-doped TiO_2 with enhanced electron-hole separation and efficient photodegradation of gaseous toluene under visible-light

    International Nuclear Information System (INIS)

    Li, Juan-Juan; Cai, Song-Cai; Xu, Zhen; Chen, Xi; Chen, Jin; Jia, Hong-Peng; Chen, Jing

    2017-01-01

    Highlights: • Bi-Zn co-doped TiO_2 catalysts were prepared by solvothermal route. • The incorporation of Bi doping into the TiO_2 generates intermediate energy levels. • Bi and Zn doping showed the enhanced absorption in visible-light region. • Zn dopant acts as a mediator of interfacial charge transfer. • TiBi_1_._9_%Zn_1_%O_2 exhibited high photocatalytic degradation for toluene. - Abstract: This study investigated the effects of Bi doped and Bi-Zn co-doped TiO_2 on photodegradation of gaseous toluene. The doped TiO_2 with various concentration of metal was prepared using the solvothermal route and characterized by SEM, XRD, Raman, BET, DRS, XPS, PL and EPR. Their photocatalytic activities under visible-light irradiation were drastically influenced by the dopant content. The results showed that moderate metal doping levels were obviously beneficial for the toluene degradation, while high doping levels suppressed the photocatalytic activity. The photocatalytic degradation of toluene over TiBi_1_._9_%O_2 and TiBi_1_._9_%Zn_1_%O_2 can reach to 51% and 93%, respectively, which are much higher than 25% of TiO_2. Bi doping into TiO_2 lattice generates new intermediate energy level of Bi below the CB edge of TiO_2. The electron excitation from the VB to Bi orbitals results in the decreased band gap, extended absorption of visible-light and thus enhances its photocatalytic efficiency. Zn doping not only further enhances the absorption in this visible-light region, but also Zn dopant exists as the form of ZnO crystallites located on the interfaces of TiO_2 agglomerates and acts as a mediator of interfacial charge transfer to suppress the electron-hole recombination. These synergistic effects are responsible for the enhanced photocatalytic performance.

  20. Electron-phonon thermalization in a scalable method for real-time quantum dynamics

    Science.gov (United States)

    Rizzi, Valerio; Todorov, Tchavdar N.; Kohanoff, Jorge J.; Correa, Alfredo A.

    2016-01-01

    We present a quantum simulation method that follows the dynamics of out-of-equilibrium many-body systems of electrons and oscillators in real time. Its cost is linear in the number of oscillators and it can probe time scales from attoseconds to hundreds of picoseconds. Contrary to Ehrenfest dynamics, it can thermalize starting from a variety of initial conditions, including electronic population inversion. While an electronic temperature can be defined in terms of a nonequilibrium entropy, a Fermi-Dirac distribution in general emerges only after thermalization. These results can be used to construct a kinetic model of electron-phonon equilibration based on the explicit quantum dynamics.

  1. Attosecond Two-Photon Interferometry for Doubly Excited States of Helium

    International Nuclear Information System (INIS)

    Feist, J.; Nagele, S.; Burgdoerfer, J.; Ticknor, C.; Collins, L. A.; Schneider, B. I.

    2011-01-01

    We show that the correlation dynamics in coherently excited doubly excited resonances of helium can be followed in real time by two-photon interferometry. This approach promises to map the evolution of the two-electron wave packet onto experimentally easily accessible noncoincident single-electron spectra. We analyze the interferometric signal in terms of a semianalytical model which is validated by a numerical solution of the time-dependent two-electron Schroedinger equation in its full dimensionality.

  2. Solvothermal syntheses of Bi and Zn co-doped TiO{sub 2} with enhanced electron-hole separation and efficient photodegradation of gaseous toluene under visible-light

    Energy Technology Data Exchange (ETDEWEB)

    Li, Juan-Juan [Center for Excellence in Regional Atmospheric Environment, and Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); Cai, Song-Cai [Center for Excellence in Regional Atmospheric Environment, and Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); University of Chinese Academy of Sciences, Beijing, 100049 (China); Xu, Zhen [Center for Excellence in Regional Atmospheric Environment, and Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); Chen, Xi [Center for Excellence in Regional Atmospheric Environment, and Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); University of Chinese Academy of Sciences, Beijing, 100049 (China); Chen, Jin [Center for Excellence in Regional Atmospheric Environment, and Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); Jia, Hong-Peng, E-mail: hpjia@iue.ac.cn [Center for Excellence in Regional Atmospheric Environment, and Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021 (China); Chen, Jing, E-mail: jing.chen@fjirsm.ac.cn [State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002 (China)

    2017-03-05

    Highlights: • Bi-Zn co-doped TiO{sub 2} catalysts were prepared by solvothermal route. • The incorporation of Bi doping into the TiO{sub 2} generates intermediate energy levels. • Bi and Zn doping showed the enhanced absorption in visible-light region. • Zn dopant acts as a mediator of interfacial charge transfer. • TiBi{sub 1.9%}Zn{sub 1%}O{sub 2} exhibited high photocatalytic degradation for toluene. - Abstract: This study investigated the effects of Bi doped and Bi-Zn co-doped TiO{sub 2} on photodegradation of gaseous toluene. The doped TiO{sub 2} with various concentration of metal was prepared using the solvothermal route and characterized by SEM, XRD, Raman, BET, DRS, XPS, PL and EPR. Their photocatalytic activities under visible-light irradiation were drastically influenced by the dopant content. The results showed that moderate metal doping levels were obviously beneficial for the toluene degradation, while high doping levels suppressed the photocatalytic activity. The photocatalytic degradation of toluene over TiBi{sub 1.9%}O{sub 2} and TiBi{sub 1.9%}Zn{sub 1%}O{sub 2} can reach to 51% and 93%, respectively, which are much higher than 25% of TiO{sub 2}. Bi doping into TiO{sub 2} lattice generates new intermediate energy level of Bi below the CB edge of TiO{sub 2}. The electron excitation from the VB to Bi orbitals results in the decreased band gap, extended absorption of visible-light and thus enhances its photocatalytic efficiency. Zn doping not only further enhances the absorption in this visible-light region, but also Zn dopant exists as the form of ZnO crystallites located on the interfaces of TiO{sub 2} agglomerates and acts as a mediator of interfacial charge transfer to suppress the electron-hole recombination. These synergistic effects are responsible for the enhanced photocatalytic performance.

  3. How to understand the tunneling in attosecond experiment?. Bohr-Einstein photon box Gedanken experiment, tunneling time and the wave particle duality

    Science.gov (United States)

    Kullie, Ossama

    2018-02-01

    The measurement of the tunneling time (T-time) in today's attosecond and strong field (low-frequency) experiments, despite its controversial discussion, offers a fruitful opportunity to understand time measurement and the time in quantum mechanics. In addition, as we will see in this work, a related controversial issue is the particulate nature of the radiation. The T-time in attosecond experiment and its different aspects and models, is discussed in this work, especially in relation to my model of real T-time (Kullie, 2015), where a good agreement with the experiment and an intriguing similarity to the Bohr-Einstein photon box Gedanken experiment was found. The tunneling process itself is still not well understood, but I am arguing that a scattering mechanism (by the laser wave packet) offers a possibility to understand the tunneling process in the tunneling region. This is related to the question about the corpuscular nature of light which is widely discussed in modern quantum optics experiments.

  4. Role of dynamical screening in excitation kinetics of biased quantum wells: Nonlinear absorption and ultrabroadband terahertz emission

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Monozon, B. S.; Jepsen, Peter Uhd

    2006-01-01

    In this work we describe the ultrafast excitation kinetics of biased quantum well, arising from the optically induced dynamical screening of a bias electric field. The initial bia electric field inside the quantum well is screened by the optically excited polarized electron-hole pairs. This leads...... wells are in good agreement with our experimental observations [Turchinovich et al., Phys. Rev. B 68, 241307(R) (2003)], as well as in perfect compliance with qualitative considerations. ©2006 American Institute of Physics...

  5. Isolated sub-100-as pulse generation via controlling electron dynamics

    International Nuclear Information System (INIS)

    Lan Pengfei; Lu Peixiang; Cao Wei; Li Yuhua; Wang Xinlin

    2007-01-01

    A method to coherently control electron dynamics is proposed using a few-cycle laser pulse in combination with a controlling field. It is shown that this method not only broadens the attosecond pulse bandwidth, but also reduces the chirp; thus an isolated 80-as pulse is straightforwardly obtained, and even shorter pulses are achievable by increasing the intensity of the controlling field. Such ultrashort pulses allow one to investigate ultrafast electronic processes. In addition, the few-cycle synthesized pulse is expected to be useful for manipulating a wide range of laser-atom interactions

  6. Ultra-short time sciences. From the atto-second to the peta-watts

    International Nuclear Information System (INIS)

    2000-01-01

    This book presents the recent advances in the scientific and technical domains linked with ultra-short time physics. It deals first with the conceptual and technological aspects of ultra-intense and ultra-brief lasers. Then, it describes the different domains of research (atoms, molecules and aggregates; gaseous phase dynamics using the pump-probe technique; femto-chemistry in dense phase; condensed matter; plasma physics; consistent control; aerosols; functional femto-biology) and the different domains of application (medical diagnosis; ophthalmology; telecommunications; technological and industrial developments). A last part is devoted to the teaching of ultra-short time sciences. (J.S.)

  7. On the 2nd order autocorrelation of an XUV attosecond pulse train

    International Nuclear Information System (INIS)

    Tzallas, P.; Benis, E.; Nikolopoulos, L.A.A.; Tsakiris, G.D.; Witte, K.; Charalambidis, P

    2005-01-01

    Full text: We present the first direct measurement of sub-fs light bunching that has been achieved, extending well established fs optical metrology to XUV as pulses. A mean train pulse duration of 780 as has been extracted through a 2 nd order autocorrelation approach, utilizing a nonlinear effect that is induced solely by the XUV radiation to be characterized. The approach is based on (i) a bisected spherical mirror XUV wavefront divider used as an autocorrelator and (ii) the two photon ionization of atomic He by a superposition of the 7 th to the 15 th harmonic of a Ti:sapph laser. The measured temporal mean width is more than twice its Fourier transform limited (FTL) value, in contrast to the as train pulse durations measured through other approaches, which where found much closer to the FTL values. We have investigated, and discuss here the origin of this discrepancy. An assessment of the validity of the 2 nd order AC approach for the broad band XUV radiation of as pulses is implemented through ab initio calculations (solution of the 3D TDSE of He in the presence of the superposition of the harmonic superposition) modeling the spectral and temporal response of the two-XUV-photon He ionization detector employed. It is found that both the spectral and temporal response are not affecting the measured duration. The mean width of the as train bursts is estimated from the spectral phases of the individual harmonics as they result from the rescattering model, taking into account the spatially modulated temporal width of the radiation due to the spatiotemporal intensity distribution of the driving field during the harmonic generation process. The measured value is found in reasonable agreement with the estimated duration. The method used for the 2 nd order AC in itself initiates further XUV-pump-XUV-probe studies of sub-fs-scale dynamics and at the same time becomes highly pertinent in connection with nonlinear experiments using XUV free - electron laser sources. Refs

  8. Dynamics

    CERN Document Server

    Goodman, Lawrence E

    2001-01-01

    Beginning text presents complete theoretical treatment of mechanical model systems and deals with technological applications. Topics include introduction to calculus of vectors, particle motion, dynamics of particle systems and plane rigid bodies, technical applications in plane motions, theory of mechanical vibrations, and more. Exercises and answers appear in each chapter.

  9. Photo-Induced Spin Dynamics in Semiconductor Quantum Wells.

    Science.gov (United States)

    Miah, M Idrish

    2009-01-17

    We experimentally investigate the dynamics of spins in GaAs quantum wells under applied electric bias by photoluminescence (PL) measurements excited with circularly polarized light. The bias-dependent circular polarization of PL (P(PL)) with and without magnetic field is studied. The P(PL) without magnetic field is found to be decayed with an enhancement of increasing the strength of the negative bias. However, P(PL) in a transverse magnetic field shows oscillations under an electric bias, indicating that the precession of electron spin occurs in quantum wells. The results are discussed based on the electron-hole exchange interaction in the electric field.

  10. Dynamic space charge behaviour in polymeric DC cables

    DEFF Research Database (Denmark)

    Rasmussen, Claus Nygaard; Holbøll, Joachim; Henriksen, Mogens

    2002-01-01

    The use of extruded insulation for DC cables involves a risk of local electric field enhancement, caused by a space charge build-up within the dielectric. In this work, the theory of charge generation and transport in polymers is applied in a numerical computer model in order to predict...... the formation and transport of space charges in a polymeric dielectric. The model incorporates the processes of field assisted electron-hole pair generation from impurity atoms, trapping and charge injection at the electrodes. Its aim has been to study the field- and temperature dependent dynamic behaviour...

  11. Applications of anomalous diffraction systems, generation of attosecond electron and photon pulses and Raman amplification by stimulated emission of radiation

    Science.gov (United States)

    Vartak, Sameer Dinkar

    1998-10-01

    efficient delivery of this power to the screen. We describe a method based on optical rectification to create an electron acceleration process which can act simultaneously on a femtosecond photo-electron pulse as well as cancel space-charge effects. This method can be used to produce attosecond electron and photon pulses. Narrow linewidth high intensity tunable light pulses are very useful for applications such as spectroscopic studies and remote sensing. Tunable lasers and stimulated Raman scattering (SRS) process are commonly used for this purpose. SRS process has high threshold because of small spontaneous Raman scattering cross-sections. We combined amplified spontaneous emission (ASE) from dye molecules with SRS process in solvent molecules in which dye molecules are dissolved. ASE seeds SRS process and SRS peak is further amplified by stimulated emission gain. We got amplifications ~100 over SRS from pure solvent. This peak can be tuned over gain bandwidth of dye molecules.

  12. Time-resolved imaging of purely valence-electron dynamics during a chemical reaction

    DEFF Research Database (Denmark)

    Hockett, Paul; Bisgaard, Christer Z.; Clarkin, Owen J.

    2011-01-01

    Chemical reactions are manifestations of the dynamics of molecular valence electrons and their couplings to atomic motions. Emerging methods in attosecond science can probe purely electronic dynamics in atomic and molecular systems(1-6). By contrast, time-resolved structural-dynamics methods...... such as electron(7-10) or X-ray diffraction(11) and X-ray absorption(12) yield complementary information about the atomic motions. Time-resolved methods that are directly sensitive to both valence-electron dynamics and atomic motions include photoelectron spectroscopy(13-15) and high-harmonic generation(16......,17): in both cases, this sensitivity derives from the ionization-matrix element(18,19). Here we demonstrate a time-resolved molecular-frame photoelectron-angular-distribution (TRMFPAD) method for imaging the purely valence-electron dynamics during a chemical reaction. Specifically, the TRMFPADs measured during...

  13. Generation of single attosecond pulse within one atomic unit by using multi-cycle inhomogeneous polarization gating technology in bowtie-shaped nanostructure

    Science.gov (United States)

    Feng, Liqiang; Liu, Hang

    2018-04-01

    The generations of high-order harmonic spectra and single attosecond pulses (SAPs) driven by the multi-cycle inhomogeneous polarization gating (PG) technology in the bowtie-shaped nanostructure have been theoretically investigated. It is found that by setting the bowtie-shaped nanostructure along the driven laser polarization direction, not only the extension of the harmonic cutoff can be achieved, caused by the surface plasmon polaritons, but also the modulations of the harmonics can be decreased, caused by the PG technology and the inhomogeneous effect. As a result, the contribution of the harmonic plateau is only from one harmonic emission peak with the dominant short quantum path. Further, by properly adding a half-cycle pulse into the driven laser field, the harmonic emission process can be precisely controlled in the half-cycle duration and a supercontinuum with the bandwidth of 263 eV can be obtained. Finally, by directly superposing the harmonics from this supercontinuum, a SAP with the full width at half maximum of 23 as can be obtained, which is shorter than one atomic unit.

  14. Density and temperature dependence of carrier dynamics in self-organized InGaAs quantum dots

    International Nuclear Information System (INIS)

    Norris, T B; Kim, K; Urayama, J; Wu, Z K; Singh, J; Bhattacharya, P K

    2005-01-01

    We have used two- and three-pulse femtosecond differential transmission spectroscopy to study the dependence of quantum dot carrier dynamics on temperature. At low temperatures and densities, the rates for relaxation between the quantum dot confined states and for capture from the barrier region into the various dot levels could be directly determined. For electron-hole pairs generated directly in the quantum dot excited state, relaxation is dominated by electron-hole scattering, and occurs on a 5 ps time scale. Capture times from the barrier into the quantum dot are of the order of 2 ps (into the excited state) and 10 ps (into the ground state). The phonon bottleneck was clearly observed in low-density capture experiments, and the conditions for its observation (namely, the suppression of electron-hole scattering for nongeminately captured electrons) were determined. As temperature increases beyond about 100 K, the dynamics become dominated by the re-emission of carriers from the lower dot levels, due to the large density of states in the wetting layer and barrier region. Measurements of the gain dynamics show fast (130 fs) gain recovery due to intradot carrier-carrier scattering, and picosecond-scale capture. Direct measurement of the transparency density versus temperature shows the dramatic effect of carrier re-emission for the quantum dots on thermally activated scattering. The carrier dynamics at elevated temperature are thus strongly dominated by the high density of the high energy continuum states relative to the dot confined levels. Deleterious hot carrier effects can be suppressed in quantum dot lasers by resonant tunnelling injection

  15. Cluster dynamics transcending chemical dynamics toward nuclear fusion.

    Science.gov (United States)

    Heidenreich, Andreas; Jortner, Joshua; Last, Isidore

    2006-07-11

    Ultrafast cluster dynamics encompasses femtosecond nuclear dynamics, attosecond electron dynamics, and electron-nuclear dynamics in ultraintense laser fields (peak intensities 10(15)-10(20) W.cm(-2)). Extreme cluster multielectron ionization produces highly charged cluster ions, e.g., (C(4+)(D(+))(4))(n) and (D(+)I(22+))(n) at I(M) = 10(18) W.cm(-2), that undergo Coulomb explosion (CE) with the production of high-energy (5 keV to 1 MeV) ions, which can trigger nuclear reactions in an assembly of exploding clusters. The laser intensity and the cluster size dependence of the dynamics and energetics of CE of (D(2))(n), (HT)(n), (CD(4))(n), (DI)(n), (CD(3)I)(n), and (CH(3)I)(n) clusters were explored by electrostatic models and molecular dynamics simulations, quantifying energetic driving effects, and kinematic run-over effects. The optimization of table-top dd nuclear fusion driven by CE of deuterium containing heteroclusters is realized for light-heavy heteroclusters of the largest size, which allows for the prevalence of cluster vertical ionization at the highest intensity of the laser field. We demonstrate a 7-orders-of-magnitude enhancement of the yield of dd nuclear fusion driven by CE of light-heavy heteroclusters as compared with (D(2))(n) clusters of the same size. Prospective applications for the attainment of table-top nucleosynthesis reactions, e.g., (12)C(P,gamma)(13)N driven by CE of (CH(3)I)(n) clusters, were explored.

  16. Signatures of attosecond electronic–nuclear dynamics in the one-photon ionization of molecular hydrogen: analytical model versus ab initio calculations

    International Nuclear Information System (INIS)

    Medišauskas, Lukas; Ivanov, Misha Yu; Morales, Felipe; Plimak, Lev; Smirnova, Olga; Palacios, Alicia; González-Castrillo, Alberto; Martín, Fernando

    2015-01-01

    We present an analytical model based on the time-dependent WKB approximation to reproduce the photoionization spectra of an H 2 molecule in the autoionization region. We explore the nondissociative channel, which is the major contribution after one-photon absorption, and we focus on the features arising in the energy differential spectra due to the interference between the direct and the autoionization pathways. These features depend on both the timescale of the electronic decay of the autoionizing state and the time evolution of the vibrational wavepacket created in this state. With full ab initio calculations and with a one-dimensional approach that only takes into account the nuclear wavepacket associated to the few relevant electronic states we compare the ground state, the autoionizing state, and the background continuum electronic states. Finally, we illustrate how these features transform from molecular-like to atomic-like by increasing the mass of the system, thus making the electronic decay time shorter than the nuclear wavepacket motion associated with the resonant state. In other words, autoionization then occurs faster than the molecular dissociation into neutrals. (paper)

  17. Isolating strong-field dynamics in molecular systems

    Science.gov (United States)

    Orenstein, Gal; Pedatzur, Oren; Uzan, Ayelet J.; Bruner, Barry D.; Mairesse, Yann; Dudovich, Nirit

    2017-05-01

    Strong-field ionization followed by recollision provides a unique pump-probe measurement which reveals a range of electronic processes, combining sub-Angstrom spatial and attosecond temporal resolution. A major limitation of this approach is imposed by the coupling between the spatial and temporal degrees of freedom. In this paper we focus on the study of high harmonic generation and demonstrate the ability to isolate the internal dynamics—decoupling the temporal information from the spatial one. By applying an in situ approach we reveal the universality of the intrinsic pump-probe measurement and establish its validity in molecular systems. When several orbitals are involved we identify the fingerprint of the transition from the single-channel case into the multiple-channel dynamics, where complex multielectron phenomena are expected to be observed.

  18. Theoretical description of excited state dynamics in nanostructures

    Science.gov (United States)

    Rubio, Angel

    2009-03-01

    There has been much progress in the synthesis and characterization of nanostructures however, there remain immense challenges in understanding their properties and interactions with external probes in order to realize their tremendous potential for applications (molecular electronics, nanoscale opto-electronic devices, light harvesting and emitting nanostructures). We will review the recent implementations of TDDFT to study the optical absorption of biological chromophores, one-dimensional polymers and layered materials. In particular we will show the effect of electron-hole attraction in those systems. Applications to the optical properties of solvated nanostructures as well as excited state dynamics in some organic molecules will be used as text cases to illustrate the performance of the approach. Work done in collaboration with A. Castro, M. Marques, X. Andrade, J.L Alonso, Pablo Echenique, L. Wirtz, A. Marini, M. Gruning, C. Rozzi, D. Varsano and E.K.U. Gross.

  19. Radiation color and electron-hole centers of serpentines

    International Nuclear Information System (INIS)

    Lyutoev, V.P.; Yukhtanov, P.P.

    1999-01-01

    Radiation-induced coloring of serpentine (Mg 3 [Si 2 O 5 ](OH) 4 ), gamma radiation dose being 30 Mrad, is studied by the ESR and absorption spectroscopy methods. It is ascertained that ionizing radiation gives rise to formation of radiation centers on the mineral basic structural elements. paramagnetic centers and coloring centers, relating to radiation centers, stem from the same type of defects - O - oxygen centers, formed as a result of radiation-induced break of OH-bonds [ru

  20. Bonding and vibrational dynamics of a large π-conjugated molecule on a metal surface

    International Nuclear Information System (INIS)

    Temirov, R; Soubatch, S; Lassise, A; Tautz, F S

    2008-01-01

    The interplay between the substrate bonding of a large π-conjugated semiconductor molecule and the dynamical properties of the metal-organic interface is studied, employing the prototypical PTCDA/Ag(111) monolayer as an example. Both the coupling of molecular vibrations to the electron-hole-pair continuum of the metal surface and the inelastic scattering of tunnelling electrons by the molecular vibrations on their passage through the molecule are considered. The results of both types of experiment are consistent with the findings of measurements which probe the geometric and electronic structure of the adsorbate-substrate complex directly; generally speaking, they can be understood in the framework of standard theories for the electron-vibron coupling. While the experiments reported here in fact provide additional qualitative insights into the substrate bonding of our π-conjugated model molecule, their detailed quantitative understanding would require a full calculation of the dynamical interface properties, which is currently not available

  1. Dynamics of charge at water-to-semiconductor interface: Case study of wet [0 0 1] anatase TiO{sub 2} nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Shuping [Department of Chemistry, University of South Dakota, Vermillion (United States); College of Chemistry, Fuzhou University, Fuzhou 350116 (China); Department of Chemistry, University of Minnesota, Minneapolis, MN 55455 (United States); Balasanthiran, Choumini [Department of Chemistry, University of South Dakota, Vermillion (United States); Tretiak, Sergei [Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Hoefelmeyer, James D. [Department of Chemistry, University of South Dakota, Vermillion (United States); Kilina, Svetlana V. [Department of Chemistry and Biochemistry, NDSU, Fargo, ND 58108 (United States); Kilin, Dmitri S., E-mail: Dmitri.Kilin@usd.edu [Department of Chemistry, University of South Dakota, Vermillion (United States); Department of Chemistry and Biochemistry, NDSU, Fargo, ND 58108 (United States)

    2016-12-20

    Highlights: • Dynamics of photoexcitations is computed for TiO{sub 2} nanowires in aqueous environment. • Aqueous TiO{sub 2} nanowires gain brighter but short-lived optical transitions. • Relaxation of electrons (holes) is 2 (4) times faster in water than in vacuum. • Calculated and experimental absorption/emission spectra correlate well. - Abstract: The behavior of water molecules on the surfaces of the TiO{sub 2} nanowire grown in [0 0 1] direction has been investigated by combining theoretical calculations and experiments. Calculated UV–visible absorption spectra reproduce the main features of the experimental spectra. Computations predict that a photoexcitation followed by a sequence of relaxation events results in photoluminescence across the gap. TiO{sub 2} nanowires in vacuum and aqueous environment exhibit different dynamics of photo-excited charge carriers. In water, computed relaxation of electrons (holes) is approximately 2 (4) times faster compared with vacuum environment. Faster relaxation of holes vs. electrons and specific spatial localization of holes result to formation of long lived charge transfer excitation with positive charge at the surface of the nanowire. Comparison of relaxation process in TiO{sub 2}/water interfaces focusing on different surfaces and nanostructures has potential in identifying structural characteristics of TiO{sub 2} materials important for efficient photo-electrochemical water splitting.

  2. Study of recombination processes for 'electron-hole' pairs in germanium irradiated by {gamma} rays from {sup 60}Co using the photovoltaic effect in P-N junctions; Etude du processus de recombinaison des paires ''electron-trou'' dans le germanium irradie par les rayons {gamma} du cobalt 60 a l'aide de l'effet photovoltaique dans les jonctions P-N

    Energy Technology Data Exchange (ETDEWEB)

    Zahedi-Mochadam, A A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-10-01

    Using the photo-voltaic effect in p-n junctions, we have studied, during bombardment, the mechanism of the recombination of 'electron-hole' pairs in the presence of structure defects produced in germanium of the N and P types by {gamma} rays from a Co{sup 60} source. At 310 K the level of the recombination centres is situated 0.25 eV above the conduction band and the capture cross-sections of the holes and of the electrons have the respective values of: {sigma}{sub p} = 4 X 10{sup -15} cm{sup 2} and {sigma}{sub n} = 3 X 10{sup -15} cm{sup 2}. The value of {sigma}{sub n} appears to be under-estimated because the number of defects in P-type samples appears to be lower than that in N-type samples. These results lead to the conclusion that the interstitials are responsible for the recombination. At 80 K it has been found that in N-type samples, a shallow level exists at O.05 eV below the conduction band with a capture cross-section for the holes of {sigma}{sub p} {>=} 10{sup -14} cm{sup 2}. We believe that in this case the recombination of charge carriers is controlled by the neighbouring 'defect-interstitial' pairs. In P-type samples at low temperature, the life-time is practically constant during irradiation. This fact is attributed to a spontaneous annealing of defects ol purely electrical origin. In the last part of the work the study of the photo-voltaic effect applied to the problem of gamma radiation dosimetry is considered. It is shown that such dosimeters, based on this principle, make it possible to measure the intensity of gamma rays over a very wide range. (author) [French] En utilisant l'effet photovoltaique dans les jonctions p-n, nous avons etudie au cours du bombardement le mecanisme de recombinaison des paires 'electron-trou' en presence des defauts de structure introduits dans le germanium de type N et de type P par les rayons gamma d'une source de Co{sup 60}. A 310 K, le niveau des centres de recombinaison se trouve a 0,25 eV au-dessous de la bande

  3. Ultrafast Electron Dynamics in Solar Energy Conversion.

    Science.gov (United States)

    Ponseca, Carlito S; Chábera, Pavel; Uhlig, Jens; Persson, Petter; Sundström, Villy

    2017-08-23

    Electrons are the workhorses of solar energy conversion. Conversion of the energy of light to electricity in photovoltaics, or to energy-rich molecules (solar fuel) through photocatalytic processes, invariably starts with photoinduced generation of energy-rich electrons. The harvesting of these electrons in practical devices rests on a series of electron transfer processes whose dynamics and efficiencies determine the function of materials and devices. To capture the energy of a photogenerated electron-hole pair in a solar cell material, charges of opposite sign have to be separated against electrostatic attractions, prevented from recombining and being transported through the active material to electrodes where they can be extracted. In photocatalytic solar fuel production, these electron processes are coupled to chemical reactions leading to storage of the energy of light in chemical bonds. With the focus on the ultrafast time scale, we here discuss the light-induced electron processes underlying the function of several molecular and hybrid materials currently under development for solar energy applications in dye or quantum dot-sensitized solar cells, polymer-fullerene polymer solar cells, organometal halide perovskite solar cells, and finally some photocatalytic systems.

  4. Subfemtosecond electron dynamics of H{sub 2} in strong fields or the quest for the molecular clock

    Energy Technology Data Exchange (ETDEWEB)

    Staudte, A.

    2005-07-01

    In this work we have studied experimentally and theoretically hydrogen and deuterium molecules in strong laser fields. We wanted to demonstrate that control of dynamical processes on the time scale below a single laser cycle (2.7 fs) can be achieved even without using attosecond pulses just by employing the advanced experimental technique COLTRIMS. In order to do this, we have pursued two goals: 1. To examine, whether laser steered electron wavepackets can be used for laser induced electron diffraction (LIED) on molecules. 2. To demonstrate, that the double ionization of H{sub 2} can be followed with sub laser cycle temporal resolution (the molecular clock). Laser induced electron diffraction needs linearly polarized light since its mechanism relies on rescattering of the ionized electron in the molecular potential. With rescattering occurring within a few hundred attoseconds, LIED is really a process of attosecond physics. In principle, two extreme scattering geometries are possible for a homonuclear diatomic molecule like H{sub 2}: the perpendicular geometry, which corresponds to the classical double slit experiment where the electron microbunch is steered transversely to the molecular axis, and the tangential geometry with the electron moving parallel to the molecular axis. Experimental restrictions prevented us to investigate the perpendicular geometry. The molecular clock, on the other hand, employs circularly polarized light to map the absolute phase of the laser electric field onto the spatial direction of the electron momentum. Thereby, a full laser cycle is mapped onto 360 in momentum space. Thus, different electron ejection angles in the laboratory frame correspond to different ejection times. Together with the correlated kinetic energy release of the Coulomb exploding molecules an unambiguous clock running from 0-8 fs with a few 100 as resolution can be envisioned. In direct relation to this experiment, we studied the influence of the long range

  5. Femtosecond-laser induced dynamics of CO on Ru(0001): Deep insights from a hot-electron friction model including surface motion

    Science.gov (United States)

    Scholz, Robert; Floß, Gereon; Saalfrank, Peter; Füchsel, Gernot; Lončarić, Ivor; Juaristi, J. I.

    2016-10-01

    A Langevin model accounting for all six molecular degrees of freedom is applied to femtosecond-laser induced, hot-electron driven dynamics of Ru(0001)(2 ×2 ):CO. In our molecular dynamics with electronic friction approach, a recently developed potential energy surface based on gradient-corrected density functional theory accounting for van der Waals interactions is adopted. Electronic friction due to the coupling of molecular degrees of freedom to electron-hole pairs in the metal are included via a local density friction approximation, and surface phonons by a generalized Langevin oscillator model. The action of ultrashort laser pulses enters through a substrate-mediated, hot-electron mechanism via a time-dependent electronic temperature (derived from a two-temperature model), causing random forces acting on the molecule. The model is applied to laser induced lateral diffusion of CO on the surface, "hot adsorbate" formation, and laser induced desorption. Reaction probabilities are strongly enhanced compared to purely thermal processes, both for diffusion and desorption. Reaction yields depend in a characteristic (nonlinear) fashion on the applied laser fluence, as well as branching ratios for various reaction channels. Computed two-pulse correlation traces for desorption and other indicators suggest that aside from electron-hole pairs, phonons play a non-negligible role for laser induced dynamics in this system, acting on a surprisingly short time scale. Our simulations on precomputed potentials allow for good statistics and the treatment of long-time dynamics (300 ps), giving insight into this system which hitherto has not been reached. We find generally good agreement with experimental data where available and make predictions in addition. A recently proposed laser induced population of physisorbed precursor states could not be observed with the present low-coverage model.

  6. Carrier thermalization dynamics in single zincblende and wurtzite InP Nanowires.

    Science.gov (United States)

    Wang, Yuda; Jackson, Howard E; Smith, Leigh M; Burgess, Tim; Paiman, Suriati; Gao, Qiang; Tan, Hark Hoe; Jagadish, Chennupati

    2014-12-10

    Using transient Rayleigh scattering (TRS) measurements, we obtain photoexcited carrier thermalization dynamics for both zincblende (ZB) and wurtzite (WZ) InP single nanowires (NW) with picosecond resolution. A phenomenological fitting model based on direct band-to-band transition theory is developed to extract the electron-hole-plasma density and temperature as a function of time from TRS measurements of single nanowires, which have complex valence band structures. We find that the thermalization dynamics of hot carriers depends strongly on material (GaAs NW vs InP NW) and less strongly on crystal structure (ZB vs WZ). The thermalization dynamics of ZB and WZ InP NWs are similar. But a comparison of the thermalization dynamics in ZB and WZ InP NWs with ZB GaAs NWs reveals more than an order of magnitude slower relaxation for the InP NWs. We interpret these results as reflecting their distinctive phonon band structures that lead to different hot phonon effects. Knowledge of hot carrier thermalization dynamics is an essential component for effective incorporation of nanowire materials into electronic devices.

  7. Molecular quantum dynamics. From theory to applications

    International Nuclear Information System (INIS)

    Gatti, Fabien

    2014-01-01

    An educational and accessible introduction to the field of molecular quantum dynamics. Illustrates the importance of the topic for broad areas of science: from astrophysics and the physics of the atmosphere, over elementary processes in chemistry, to biological processes. Presents chosen examples of striking applications, highlighting success stories, summarized by the internationally renowned experts. Including a foreword by Lorenz Cederbaum (University Heidelberg, Germany). This book focuses on current applications of molecular quantum dynamics. Examples from all main subjects in the field, presented by the internationally renowned experts, illustrate the importance of the domain. Recent success in helping to understand experimental observations in fields like heterogeneous catalysis, photochemistry, reactive scattering, optical spectroscopy, or femto- and attosecond chemistry and spectroscopy underline that nuclear quantum mechanical effects affect many areas of chemical and physical research. In contrast to standard quantum chemistry calculations, where the nuclei are treated classically, molecular quantum dynamics can cover quantum mechanical effects in their motion. Many examples, ranging from fundamental to applied problems, are known today that are impacted by nuclear quantum mechanical effects, including phenomena like tunneling, zero point energy effects, or non-adiabatic transitions. Being important to correctly understand many observations in chemical, organic and biological systems, or for the understanding of molecular spectroscopy, the range of applications covered in this book comprises broad areas of science: from astrophysics and the physics and chemistry of the atmosphere, over elementary processes in chemistry, to biological processes (such as the first steps of photosynthesis or vision). Nevertheless, many researchers refrain from entering this domain. The book ''Molecular Quantum Dynamics'' offers them an accessible introduction. Although the

  8. Molecular quantum dynamics. From theory to applications

    Energy Technology Data Exchange (ETDEWEB)

    Gatti, Fabien (ed.) [Montpellier 2 Univ. (France). Inst. Charles Gerhardt - CNRS 5253

    2014-09-01

    An educational and accessible introduction to the field of molecular quantum dynamics. Illustrates the importance of the topic for broad areas of science: from astrophysics and the physics of the atmosphere, over elementary processes in chemistry, to biological processes. Presents chosen examples of striking applications, highlighting success stories, summarized by the internationally renowned experts. Including a foreword by Lorenz Cederbaum (University Heidelberg, Germany). This book focuses on current applications of molecular quantum dynamics. Examples from all main subjects in the field, presented by the internationally renowned experts, illustrate the importance of the domain. Recent success in helping to understand experimental observations in fields like heterogeneous catalysis, photochemistry, reactive scattering, optical spectroscopy, or femto- and attosecond chemistry and spectroscopy underline that nuclear quantum mechanical effects affect many areas of chemical and physical research. In contrast to standard quantum chemistry calculations, where the nuclei are treated classically, molecular quantum dynamics can cover quantum mechanical effects in their motion. Many examples, ranging from fundamental to applied problems, are known today that are impacted by nuclear quantum mechanical effects, including phenomena like tunneling, zero point energy effects, or non-adiabatic transitions. Being important to correctly understand many observations in chemical, organic and biological systems, or for the understanding of molecular spectroscopy, the range of applications covered in this book comprises broad areas of science: from astrophysics and the physics and chemistry of the atmosphere, over elementary processes in chemistry, to biological processes (such as the first steps of photosynthesis or vision). Nevertheless, many researchers refrain from entering this domain. The book ''Molecular Quantum Dynamics'' offers them an accessible

  9. Time-resolved photoelectron spectroscopy of IR-driven electron dynamics in a charge transfer model system.

    Science.gov (United States)

    Falge, Mirjam; Fröbel, Friedrich Georg; Engel, Volker; Gräfe, Stefanie

    2017-08-02

    If the adiabatic approximation is valid, electrons smoothly adapt to molecular geometry changes. In contrast, as a characteristic of diabatic dynamics, the electron density does not follow the nuclear motion. Recently, we have shown that the asymmetry in time-resolved photoelectron spectra serves as a tool to distinguish between these dynamics [Falge et al., J. Phys. Chem. Lett., 2012, 3, 2617]. Here, we investigate the influence of an additional, moderately intense infrared (IR) laser field, as often applied in attosecond time-resolved experiments, on such asymmetries. This is done using a simple model for coupled electronic-nuclear motion. We calculate time-resolved photoelectron spectra and their asymmetries and demonstrate that the spectra directly map the bound electron-nuclear dynamics. From the asymmetries, we can trace the IR field-induced population transfer and both the field-driven and intrinsic (non-)adiabatic dynamics. This holds true when considering superposition states accompanied by electronic coherences. The latter are observable in the asymmetries for sufficiently short XUV pulses to coherently probe the coupled states. It is thus documented that the asymmetry is a measure for phases in bound electron wave packets and non-adiabatic dynamics.

  10. New theoretical approaches to atomic and molecular dynamics triggered by ultrashort light pulses on the atto- to picosecond time scale

    International Nuclear Information System (INIS)

    Pabst, Stefan Ulf

    2013-04-01

    The concept of atoms as the building blocks of matter has existed for over 3000 years. A revolution in the understanding and the description of atoms and molecules has occurred in the last century with the birth of quantum mechanics. After the electronic structure was understood, interest in studying the dynamics of electrons, atoms, and molecules increased. However, time-resolved investigations of these ultrafast processes were not possible until recently. The typical time scale of atomic and molecular processes is in the picosecond to attosecond realm. Tremendous technological progress in recent years makes it possible to generate light pulses on these time scales. With such ultrashort pulses, atomic and molecular dynamics can be triggered, watched, and controlled. Simultaneously, the need rises for theoretical models describing the underlying mechanisms. This doctoral thesis focuses on the development of theoretical models which can be used to study the dynamical behavior of electrons, atoms, and molecules in the presence of ultrashort light pulses. Several examples are discussed illustrating how light pulses can trigger and control electronic, atomic, and molecular motions. In the first part of this work, I focus on the rotational motion of asymmetric molecules, which happens on picosecond and femtosecond time scales. Here, the aim is to align all three axes of the molecule as well as possible. To investigate theoretically alignment dynamics, I developed a program that can describe alignment motion ranging from the impulsive to the adiabatic regime. The asymmetric molecule SO 2 is taken as an example to discuss strategies of optimizing 3D alignment without the presence of an external field (i.e., field-free alignment). Field-free alignment is particularly advantageous because subsequent experiments on the aligned molecule are not perturbed by the aligning light pulse. Wellaligned molecules in the gas phase are suitable for diffraction experiments. From the

  11. New theoretical approaches to atomic and molecular dynamics triggered by ultrashort light pulses on the atto- to picosecond time scale

    Energy Technology Data Exchange (ETDEWEB)

    Pabst, Stefan Ulf

    2013-04-15

    The concept of atoms as the building blocks of matter has existed for over 3000 years. A revolution in the understanding and the description of atoms and molecules has occurred in the last century with the birth of quantum mechanics. After the electronic structure was understood, interest in studying the dynamics of electrons, atoms, and molecules increased. However, time-resolved investigations of these ultrafast processes were not possible until recently. The typical time scale of atomic and molecular processes is in the picosecond to attosecond realm. Tremendous technological progress in recent years makes it possible to generate light pulses on these time scales. With such ultrashort pulses, atomic and molecular dynamics can be triggered, watched, and controlled. Simultaneously, the need rises for theoretical models describing the underlying mechanisms. This doctoral thesis focuses on the development of theoretical models which can be used to study the dynamical behavior of electrons, atoms, and molecules in the presence of ultrashort light pulses. Several examples are discussed illustrating how light pulses can trigger and control electronic, atomic, and molecular motions. In the first part of this work, I focus on the rotational motion of asymmetric molecules, which happens on picosecond and femtosecond time scales. Here, the aim is to align all three axes of the molecule as well as possible. To investigate theoretically alignment dynamics, I developed a program that can describe alignment motion ranging from the impulsive to the adiabatic regime. The asymmetric molecule SO{sub 2} is taken as an example to discuss strategies of optimizing 3D alignment without the presence of an external field (i.e., field-free alignment). Field-free alignment is particularly advantageous because subsequent experiments on the aligned molecule are not perturbed by the aligning light pulse. Wellaligned molecules in the gas phase are suitable for diffraction experiments. From the

  12. Multi-purpose two- and three-dimensional momentum imaging of charged particles for attosecond experiments at 1 kHz repetition rate

    Energy Technology Data Exchange (ETDEWEB)

    Månsson, Erik P., E-mail: erik.mansson@sljus.lu.se; Sorensen, Stacey L.; Gisselbrecht, Mathieu [Division of Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund (Sweden); Arnold, Cord L.; Kroon, David; Guénot, Diego; Fordell, Thomas; Johnsson, Per; L’Huillier, Anne [Division of Atomic Physics, Lund University, Box 118, 221 00 Lund (Sweden); Lépine, Franck [Institut Lumière Matière, UMR5306, Université Lyon 1-CNRS, 10 rue Ada Byron, 69622 Villeurbanne cedex (France)

    2014-12-15

    We report on the versatile design and operation of a two-sided spectrometer for the imaging of charged-particle momenta in two dimensions (2D) and three dimensions (3D). The benefits of 3D detection are to discern particles of different mass and to study correlations between fragments from multi-ionization processes, while 2D detectors are more efficient for single-ionization applications. Combining these detector types in one instrument allows us to detect positive and negative particles simultaneously and to reduce acquisition times by using the 2D detector at a higher ionization rate when the third dimension is not required. The combined access to electronic and nuclear dynamics available when both sides are used together is important for studying photoreactions in samples of increasing complexity. The possibilities and limitations of 3D momentum imaging of electrons or ions in the same spectrometer geometry are investigated analytically and three different modes of operation demonstrated experimentally, with infrared or extreme ultraviolet light and an atomic/molecular beam.

  13. Transverse Space-Charge Field-Induced Plasma Dynamics for Ultraintense Electron-Beam Characterization

    Directory of Open Access Journals (Sweden)

    R. Tarkeshian

    2018-05-01

    Full Text Available Similarly to laser or x-ray beams, the interaction of sufficiently intense particle beams with neutral gases will result in the creation of plasma. In contrast to photon-based ionization, the strong unipolar field of a particle beam can generate a plasma where the electron population receives a large initial momentum kick and escapes, leaving behind unshielded ions. Measuring the properties of the ensuing Coulomb exploding ions—such as their kinetic energy distribution, yield, and spatial distribution—can provide information about the peak electric fields that are achieved in the electron beams. Particle-in-cell simulations and analytical models are presented for high-brightness electron beams of a few femtoseconds or even hundreds of attoseconds, and transverse beam sizes on the micron scale, as generated by today’s free electron lasers. Different density regimes for the utilization as a potential diagnostics are explored, and the fundamental differences in plasma dynamical behavior for e-beam or photon-based ionization are highlighted. By measuring the dynamics of field-induced ions for different gas and beam densities, a lower bound on the beam charge density can be obtained in a single shot and in a noninvasive way. The exponential dependency of the ionization yield on the beam properties can provide unprecedented spatial and temporal resolution, at the submicrometer and subfemtosecond scales, respectively, offering a practical and powerful approach to characterizing beams from accelerators at the frontiers of performance.

  14. Real-Space Imaging of Carrier Dynamics of Materials Surfaces by Second-Generation Four-Dimensional Scanning Ultrafast Electron Microscopy

    KAUST Repository

    Sun, Jingya

    2015-09-14

    In the fields of photocatalysis and photovoltaics, ultrafast dynamical processes, including carrier trapping and recombination on material surfaces, are among the key factors that determine the overall energy conversion efficiency. A precise knowledge of these dynamical events on the nanometer (nm) and femtosecond (fs) scales was not accessible until recently. The only way to access such fundamental processes fully is to map the surface dynamics selectively in real space and time. In this study, we establish a second generation of four-dimensional scanning ultrafast electron microscopy (4D S-UEM) and demonstrate the ability to record time-resolved images (snapshots) of material surfaces with 650 fs and ∼5 nm temporal and spatial resolutions, respectively. In this method, the surface of a specimen is excited by a clocking optical pulse and imaged using a pulsed primary electron beam as a probe pulse, generating secondary electrons (SEs), which are emitted from the surface of the specimen in a manner that is sensitive to the local electron/hole density. This method provides direct and controllable information regarding surface dynamics. We clearly demonstrate how the surface morphology, grains, defects, and nanostructured features can significantly impact the overall dynamical processes on the surface of photoactive-materials. In addition, the ability to access two regimes of dynamical probing in a single experiment and the energy loss of SEs in semiconductor-nanoscale materials will also be discussed.

  15. Emission dynamics of hybrid plasmonic gold/organic GaN nanorods

    Science.gov (United States)

    Mohammadi, F.; Schmitzer, H.; Kunert, G.; Hommel, D.; Ge, J.; Duscher, G.; Langbein, W.; Wagner, H. P.

    2017-12-01

    We studied the emission of bare and aluminum quinoline (Alq3)/gold coated wurtzite GaN nanorods by temperature- and intensity-dependent time-integrated and time-resolved photoluminescence (PL). The GaN nanorods of ˜1.5 μm length and ˜250 nm diameter were grown by plasma-assisted molecular beam epitaxy. Gold/Alq3 coated GaN nanorods were synthesized by organic molecular beam deposition. The near band-edge and donor-acceptor pair luminescence was investigated in bare GaN nanorods and compared with multilevel model calculations providing the dynamical parameters for electron-hole pairs, excitons, impurity bound excitons, donors and acceptors. Subsequently, the influence of a 10 nm gold coating without and with an Alq3 spacer layer was studied and the experimental results were analyzed with the multilevel model. Without a spacer layer, a significant PL quenching and lifetime reduction of the near band-edge emission is found. The behavior is attributed to surface band-bending and Förster energy transfer from excitons to surface plasmons in the gold layer. Inserting a 5 nm Alq3 spacer layer reduces the PL quenching and lifetime reduction which is consistent with a reduced band-bending and Förster energy transfer. Increasing the spacer layer to 30 nm results in lifetimes which are similar to uncoated structures, showing a significantly decreased influence of the gold coating on the excitonic dynamics.

  16. Polarization Effects in Attosecond Photoelectron Spectroscopy

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Madsen, Lars Bojer

    2010-01-01

    following the field instead. We show that polarization effects may lead to an apparent temporal shift that needs to be properly accounted for in the analysis. The effect may be isolated and studied by angle-resolved photoelectron spectroscopy from oriented polar molecules. We also show that polarization...... effects will lead to an apparent temporal shift of 50 as between photoelectrons from a 2p and 1s state in atomic hydrogen....

  17. Vibrational lifetimes of hydrogen on lead films: An ab initio molecular dynamics with electronic friction (AIMDEF) study

    Energy Technology Data Exchange (ETDEWEB)

    Saalfrank, Peter [Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, D-14476 Potsdam (Germany); Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián (Spain); Juaristi, J. I. [Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián (Spain); Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU), Paseo Manuel de Lardizabal 5, 20018 Donostia-San Sebastián (Spain); Departamento de Física de Materiales, Facultad de Químicas UPV/EHU, Apartado 1072, 20018 Donostia-San Sebastián (Spain); Alducin, M.; Muiño, R. Díez [Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián (Spain); Centro de Física de Materiales CFM/MPC (CSIC-UPV/EHU), Paseo Manuel de Lardizabal 5, 20018 Donostia-San Sebastián (Spain); Blanco-Rey, M. [Donostia International Physics Center (DIPC), Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián (Spain); Departamento de Física de Materiales, Facultad de Químicas UPV/EHU, Apartado 1072, 20018 Donostia-San Sebastián (Spain)

    2014-12-21

    Using density functional theory and Ab Initio Molecular Dynamics with Electronic Friction (AIMDEF), we study the adsorption and dissipative vibrational dynamics of hydrogen atoms chemisorbed on free-standing lead films of increasing thickness. Lead films are known for their oscillatory behaviour of certain properties with increasing thickness, e.g., energy and electron spillout change in discontinuous manner, due to quantum size effects [G. Materzanini, P. Saalfrank, and P. J. D. Lindan, Phys. Rev. B 63, 235405 (2001)]. Here, we demonstrate that oscillatory features arise also for hydrogen when chemisorbed on lead films. Besides stationary properties of the adsorbate, we concentrate on finite vibrational lifetimes of H-surface vibrations. As shown by AIMDEF, the damping via vibration-electron hole pair coupling dominates clearly over the vibration-phonon channel, in particular for high-frequency modes. Vibrational relaxation times are a characteristic function of layer thickness due to the oscillating behaviour of the embedding surface electronic density. Implications derived from AIMDEF for frictional many-atom dynamics, and physisorbed species will also be given.

  18. Dynamical coupling of plasmons and molecular excitations by hybrid quantum/classical calculations: time-domain approach

    International Nuclear Information System (INIS)

    Sakko, Arto; Rossi, Tuomas P; Nieminen, Risto M

    2014-01-01

    The presence of plasmonic material influences the optical properties of nearby molecules in untrivial ways due to the dynamical plasmon-molecule coupling. We combine quantum and classical calculation schemes to study this phenomenon in a hybrid system that consists of a Na 2 molecule located in the gap between two Au/Ag nanoparticles. The molecule is treated quantum-mechanically with time-dependent density-functional theory, and the nanoparticles with quasistatic classical electrodynamics. The nanoparticle dimer has a plasmon resonance in the visible part of the electromagnetic spectrum, and the Na 2 molecule has an electron-hole excitation in the same energy range. Due to the dynamical interaction of the two subsystems the plasmon and the molecular excitations couple, creating a hybridized molecular-plasmon excited state. This state has unique properties that yield e.g. enhanced photoabsorption compared to the freestanding Na 2 molecule. The computational approach used enables decoupling of the mutual plasmon-molecule interaction, and our analysis verifies that it is not legitimate to neglect the backcoupling effect when describing the dynamical interaction between plasmonic material and nearby molecules. Time-resolved analysis shows nearly instantaneous formation of the coupled state, and provides an intuitive picture of the underlying physics. (paper)

  19. Density matrix-based time-dependent configuration interaction approach to ultrafast spin-flip dynamics

    Science.gov (United States)

    Wang, Huihui; Bokarev, Sergey I.; Aziz, Saadullah G.; Kühn, Oliver

    2017-08-01

    Recent developments in attosecond spectroscopy yield access to the correlated motion of electrons on their intrinsic timescales. Spin-flip dynamics is usually considered in the context of valence electronic states, where spin-orbit coupling is weak and processes related to the electron spin are usually driven by nuclear motion. However, for core-excited states, where the core-hole has a nonzero angular momentum, spin-orbit coupling is strong enough to drive spin-flips on a much shorter timescale. Using density matrix-based time-dependent restricted active space configuration interaction including spin-orbit coupling, we address an unprecedentedly short spin-crossover for the example of L-edge (2p→3d) excited states of a prototypical Fe(II) complex. This process occurs on a timescale, which is faster than that of Auger decay (∼4 fs) treated here explicitly. Modest variations of carrier frequency and pulse duration can lead to substantial changes in the spin-state yield, suggesting its control by soft X-ray light.

  20. Time-Domain Ab Initio Analysis of Excitation Dynamics in a Quantum Dot/Polymer Hybrid: Atomistic Description Rationalizes Experiment.

    Science.gov (United States)

    Long, Run; Prezhdo, Oleg V

    2015-07-08

    Hybrid organic/inorganic polymer/quantum dot (QD) solar cells are an attractive alternative to the traditional cells. The original, simple models postulate that one-dimensional polymers have continuous energy levels, while zero-dimensional QDs exhibit atom-like electronic structure. A realistic, atomistic viewpoint provides an alternative description. Electronic states in polymers are molecule-like: finite in size and discrete in energy. QDs are composed of many atoms and have high, bulk-like densities of states. We employ ab initio time-domain simulation to model the experimentally observed ultrafast photoinduced dynamics in a QD/polymer hybrid and show that an atomistic description is essential for understanding the time-resolved experimental data. Both electron and hole transfers across the interface exhibit subpicosecond time scales. The interfacial processes are fast due to strong electronic donor-acceptor, as evidenced by the densities of the photoexcited states which are delocalized between the donor and the acceptor. The nonadiabatic charge-phonon coupling is also strong, especially in the polymer, resulting in rapid energy losses. The electron transfer from the polymer is notably faster than the hole transfer from the QD, due to a significantly higher density of acceptor states. The stronger molecule-like electronic and charge-phonon coupling in the polymer rationalizes why the electron-hole recombination inside the polymer is several orders of magnitude faster than in the QD. As a result, experiments exhibit multiple transfer times for the long-lived hole inside the QD, ranging from subpicoseconds to nanoseconds. In contrast, transfer of the short-lived electron inside the polymer does not occur beyond the first picosecond. The energy lost by the hole on its transit into the polymer is accommodated by polymer's high-frequency vibrations. The energy lost by the electron injected into the QD is accommodated primarily by much lower-frequency collective and

  1. System dynamics

    International Nuclear Information System (INIS)

    Kim, Do Hun; Mun, Tae Hun; Kim, Dong Hwan

    1999-02-01

    This book introduces systems thinking and conceptual tool and modeling tool of dynamics system such as tragedy of single thinking, accessible way of system dynamics, feedback structure and causal loop diagram analysis, basic of system dynamics modeling, causal loop diagram and system dynamics modeling, information delay modeling, discovery and application for policy, modeling of crisis of agricultural and stock breeding products, dynamic model and lesson in ecosystem, development and decadence of cites and innovation of education forward system thinking.

  2. Space- and time-dependent quantum dynamics of spatially indirect excitons in semiconductor heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Grasselli, Federico, E-mail: federico.grasselli@unimore.it; Goldoni, Guido, E-mail: guido.goldoni@unimore.it [Department of Physics, Informatics and Mathematics, University of Modena and Reggio Emilia, Modena (Italy); CNR-NANO S3, Institute for Nanoscience, Via Campi 213/a, 41125 Modena (Italy); Bertoni, Andrea, E-mail: andrea.bertoni@nano.cnr.it [CNR-NANO S3, Institute for Nanoscience, Via Campi 213/a, 41125 Modena (Italy)

    2015-01-21

    We study the unitary propagation of a two-particle one-dimensional Schrödinger equation by means of the Split-Step Fourier method, to study the coherent evolution of a spatially indirect exciton (IX) in semiconductor heterostructures. The mutual Coulomb interaction of the electron-hole pair and the electrostatic potentials generated by external gates and acting on the two particles separately are taken into account exactly in the two-particle dynamics. As relevant examples, step/downhill and barrier/well potential profiles are considered. The space- and time-dependent evolutions during the scattering event as well as the asymptotic time behavior are analyzed. For typical parameters of GaAs-based devices, the transmission or reflection of the pair turns out to be a complex two-particle process, due to comparable and competing Coulomb, electrostatic, and kinetic energy scales. Depending on the intensity and anisotropy of the scattering potentials, the quantum evolution may result in excitation of the IX internal degrees of freedom, dissociation of the pair, or transmission in small periodic IX wavepackets due to dwelling of one particle in the barrier region. We discuss the occurrence of each process in the full parameter space of the scattering potentials and the relevance of our results for current excitronic technologies.

  3. A dynamic Monte Carlo study of anomalous current voltage behaviour in organic solar cells

    International Nuclear Information System (INIS)

    Feron, K.; Fell, C. J.; Zhou, X.; Belcher, W. J.; Dastoor, P. C.

    2014-01-01

    We present a dynamic Monte Carlo (DMC) study of s-shaped current-voltage (I-V) behaviour in organic solar cells. This anomalous behaviour causes a substantial decrease in fill factor and thus power conversion efficiency. We show that this s-shaped behaviour is induced by charge traps that are located at the electrode interface rather than in the bulk of the active layer, and that the anomaly becomes more pronounced with increasing trap depth or density. Furthermore, the s-shape anomaly is correlated with interface recombination, but not bulk recombination, thus highlighting the importance of controlling the electrode interface. While thermal annealing is known to remove the s-shape anomaly, the reason has been not clear, since these treatments induce multiple simultaneous changes to the organic solar cell structure. The DMC modelling indicates that it is the removal of aluminium clusters at the electrode, which act as charge traps, that removes the anomalous I-V behaviour. Finally, this work shows that the s-shape becomes less pronounced with increasing electron-hole recombination rate; suggesting that efficient organic photovoltaic material systems are more susceptible to these electrode interface effects

  4. SELF-HEALING NANOMATERIALS: MULTIMILLION-ATOM REACTIVE MOLECULAR DYNAMICS SIMULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Hakamata, Tomoya [Kumamoto Univ., Kumamoto (Japan); Shimamura, Kohei [Kumamoto Univ., Kumamoto (Japan); Univ. of Southern California, Los Angeles, CA (United States); Kobe Univ., Kobe (Japan); Shimojo, Fuyuki [Kumamoto Univ., Kumamoto (Japan); Kalia, Rajiv K. [Univ. of Southern California, Los Angeles, CA (United States); Nakano, Aiichiro [Univ. of Southern California, Los Angeles, CA (United States); Vashishta, Priya [Univ. of Southern California, Los Angeles, CA (United States)

    2017-10-20

    Organometal halide perovskites are attracting great attention as promising material for solar cells because of their high power conversion efficiency. The high performance has been attributed to the existence of free charge carriers and their large diffusion lengths, but the nature of carrier transport at the atomistic level remains elusive. Here, nonadiabatic quantum molecular dynamics simulations elucidate the mechanisms underlying the excellent free-carrier transport in CH3NH3PbI3. Pb and I sublattices act as disjunct pathways for rapid and balanced transport of photoexcited electrons and holes, respectively, while minimizing efficiency-degrading charge recombination. On the other hand, CH3NH3 sublattice quickly screens out electrostatic electron-hole attraction to generate free carriers within 1 ps. Together this nano-architecture lets photoexcited electrons and holes dissociate instantaneously and travel far away to be harvested before dissipated as heat. As a result, this work provides much needed structure-property relationships and time-resolved information that potentially lead to rational design of efficient solar cells.

  5. Electronic structure and electron dynamics at Si(100)

    Energy Technology Data Exchange (ETDEWEB)

    Weinelt, M. [Universitaet Erlangen-Nuernberg, Lehrstuhl fuer Festkoerperphysik, Erlangen (Germany); Max-Born-Institut, Berlin (Germany); Kutschera, M.; Schmidt, R.; Orth, C.; Fauster, T. [Universitaet Erlangen-Nuernberg, Lehrstuhl fuer Festkoerperphysik, Erlangen (Germany); Rohlfing, M. [International University Bremen, School of Engineering and Science, P.O. Box 750 561, Bremen (Germany)

    2005-02-01

    The electronic structure and electron dynamics at a Si(100) surface is studied by two-photon photoemission (2PPE). At 90 K the occupied D{sub up} dangling-bond state is located 150{+-}50 meV below the valence-band maximum (VBM) at the center of the surface Brillouin zone anti {gamma} and exhibits an effective hole mass of (0.5{+-}0.15)m{sub e}. The unoccupied D{sub down} band has a local minimum at anti {gamma} at 650{+-}50 meV above the VBM and shows strong dispersion along the dimer rows of the c(4 x 2) reconstructed surface. At 300 K the D{sub down} position shifts comparable to the Si conduction-band minimum by 40 meV to lower energies but the dispersion of the dangling-bond states is independent of temperature. The surface band bending for p-doped silicon is less than 30 meV, while acceptor-type defects cause significant and preparation-dependent band bending on n-doped samples. 2PPE spectra of Si(100) are dominated by interband transitions between the occupied and unoccupied surface states and emission out of transiently and permanently charged surface defects. Including electron-hole interaction in many-body calculations of the quasi-particle band structure leads us to assign a dangling-bond split-off state to a quasi-one-dimensional surface exciton with a binding energy of 130 meV. Electrons resonantly excited to the unoccupied D{sub down} dangling-bond band with an excess energy of about 350 meV need 1.5{+-}0.2 ps to scatter via phonon emission to the band bottom at anti {gamma} and relax within 5 ps with an excited hole in the occupied surface band to form an exciton living for nanoseconds. (orig.)

  6. Quantum State-Resolved Collision Dynamics of Nitric Oxide at Ionic Liquid and Molten Metal Surfaces

    Science.gov (United States)

    Zutz, Amelia Marie

    Detailed molecular scale interactions at the gas-liquid interface are explored with quantum state-to-state resolved scattering of a jet-cooled beam of NO(2pi1/2; N = 0) from ionic liquid and molten metal surfaces. The scattered distributions are probed via laser-induced fluorescence methods, which yield rotational and spin-orbit state populations that elucidate the dynamics of energy transfer at the gas-liquid interface. These collision dynamics are explored as a function of incident collision energy, surface temperature, scattering angle, and liquid identity, all of which are found to substantially affect the degree of rotational, electronic and vibrational excitation of NO via collisions at the liquid surface. Rotational distributions observed reveal two distinct scattering pathways, (i) molecules that trap, thermalize and eventually desorb from the surface (trapping-desorption, TD), and (ii) those that undergo prompt recoil (impulsive scattering, IS) prior to complete equilibration with the liquid surface. Thermally desorbing NO molecules are found to have rotational temperatures close to, but slightly cooler than the surface temperature, indicative of rotational dependent sticking probabilities on liquid surfaces. Nitric oxide is a radical with multiple low-lying electronic states that serves as an ideal candidate for exploring nonadiabatic state-changing collision dynamics at the gas-liquid interface, which induce significant excitation from ground (2pi1/2) to excited (2pi 3/2) spin-orbit states. Molecular beam scattering of supersonically cooled NO from hot molten metals (Ga and Au, Ts = 300 - 1400 K) is also explored, which provide preliminary evidence for vibrational excitation of NO mediated by thermally populated electron-hole pairs in the hot, conducting liquid metals. The results highlight the presence of electronically nonadiabatic effects and build toward a more complete characterization of energy transfer dynamics at gas-liquid interfaces.

  7. Chemical dynamics of the first proton-coupled electron transfer of water oxidation on TiO2 anatase.

    Science.gov (United States)

    Chen, Jia; Li, Ye-Fei; Sit, Patrick; Selloni, Annabella

    2013-12-18

    Titanium dioxide (TiO2) is a prototype, water-splitting (photo)catalyst, but its performance is limited by the large overpotential for the oxygen evolution reaction (OER). We report here a first-principles density functional theory study of the chemical dynamics of the first proton-coupled electron transfer (PCET), which is considered responsible for the large OER overpotential on TiO2. We use a periodic model of the TiO2/water interface that includes a slab of anatase TiO2 and explicit water molecules, sample the solvent configurations by first principles molecular dynamics, and determine the energy profiles of the two electronic states involved in the electron transfer (ET) by hybrid functional calculations. Our results suggest that the first PCET is sequential, with the ET following the proton transfer. The ET occurs via an inner sphere process, which is facilitated by a state in which one electronic hole is shared by the two oxygen ions involved in the transfer.

  8. Theory of Weak Bipolar Fields and Electron Holes with Applications to Space Plasmas

    International Nuclear Information System (INIS)

    Goldman, Martin V.; Newman, David L.; Mangeney, Andre

    2007-01-01

    A theoretical model of weak electron phase-space holes is used to interpret bipolar field structures observed in space. In the limit eφ max /T e max sech 4 (x/α), where φ max depends on the derivative of the trapped distribution at the separatrix, while α depends only on a screening integral over the untrapped distribution. Idealized trapped and passing electron distributions are inferred from the speed, amplitude, and shape of satellite waveform measurements of weak bipolar field structures

  9. Carrier drift transport of freezed-to-electron-hole-plasma indium

    International Nuclear Information System (INIS)

    Kopylov, V.N.; Yanchenko, S.S.

    1985-01-01

    Observation of galvanomagnetic waves in indium caused by carrier drift in a superposed electric field is reported. Experiments have shown the wave propagation to be of a unidirectional character. Characteristic ime of attenuation for the investigated sample (a approximately 4 cm, rho sub(300)/rho sub(T→0) approximately 4x10 5 ) is about 5s. Increase in temperature from 1.4 K to 4.2 K resulted in a higher wave attenuation, which is associated with growth (25 fold) of resistance for both the life time of excitations and drift current induced in the sample decrease. Thus, the presence of direct current can essentially change the electrodynamic properties of specific metal

  10. Enhancement of tunnel conductivity by Cooper pair fluctuations in electron-hole bilayer

    International Nuclear Information System (INIS)

    Efimkin, D K; Lozovik, Yu E

    2012-01-01

    Influence of Cooper pair fluctuations that are precursor of pairing of electrons and holes located on opposite surfaces of topological insulator film on tunnel conductivity between the surfaces is investigated. Due to restrictions caused by momentum and energy conservation dependence of tunnel conductivity on external bias voltage has peak that becomes more prominent with decreasing of disorder and temperature. We have shown that Cooper pair fluctuations considerably enhance tunneling and height of the peak diverges in vicinity of critical temperature with critical index ν = 2. Width of the peak tends to zero in proximity of critical temperature. Pairing of electrons and holes can be suppressed by disorder and in vicinity of quantum critical point height of the peak also diverges as function of Cooper pair damping with critical index μ = 2.

  11. Landau damping effects on collision-induced quantum interference in electron-hole plasmas

    International Nuclear Information System (INIS)

    Hwa-Min, Kim; Young-Dae, Jung

    2007-01-01

    The Landau damping effects on the quantum interference in electron collisions are investigated in a quantum plasma composed of electrons and holes. The Born method and the total spin states are considered to obtain the scattering cross-section by using the effective screened potential model. It is found that the Landau damping effects enhance the scattering cross-section, especially, near the scattering angle θ L = π/4. (authors)

  12. Landau damping effects on collision-induced quantum interference in electron-hole plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Hwa-Min, Kim [Daegu Univ. Catholic, Dept. of Electronics Engineering (Korea, Republic of); Young-Dae, Jung [Hanyang Univ., Dept. of Applied Physics, Seoul (Korea, Republic of)

    2007-07-15

    The Landau damping effects on the quantum interference in electron collisions are investigated in a quantum plasma composed of electrons and holes. The Born method and the total spin states are considered to obtain the scattering cross-section by using the effective screened potential model. It is found that the Landau damping effects enhance the scattering cross-section, especially, near the scattering angle {theta}{sub L} = {pi}/4. (authors)

  13. Effects of model approximations for electron, hole, and photon transport in swift heavy ion tracks

    Energy Technology Data Exchange (ETDEWEB)

    Rymzhanov, R.A. [Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region (Russian Federation); Medvedev, N.A., E-mail: nikita.medvedev@fzu.cz [Department of Radiation and Chemical Physics, Institute of Physics, Czech Academy of Sciences, Na Slovance 2, 182 21 Prague 8 (Czech Republic); Laser Plasma Department, Institute of Plasma Physics, Czech Academy of Sciences, Za Slovankou 3, 182 00 Prague 8 (Czech Republic); Volkov, A.E. [Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region (Russian Federation); National Research Centre ‘Kurchatov Institute’, Kurchatov Sq. 1, 123182 Moscow (Russian Federation); Lebedev Physical Institute of the Russian Academy of Sciences, Leninskij pr., 53,119991 Moscow (Russian Federation); National University of Science and Technology MISiS, Leninskij pr., 4, 119049 Moscow (Russian Federation); National Research Nuclear University MEPhI, Kashirskoye sh., 31, 115409 Moscow (Russian Federation)

    2016-12-01

    The event-by-event Monte Carlo code, TREKIS, was recently developed to describe excitation of the electron subsystems of solids in the nanometric vicinity of a trajectory of a nonrelativistic swift heavy ion (SHI) decelerated in the electronic stopping regime. The complex dielectric function (CDF) formalism was applied in the used cross sections to account for collective response of a matter to excitation. Using this model we investigate effects of the basic assumptions on the modeled kinetics of the electronic subsystem which ultimately determine parameters of an excited material in an SHI track. In particular, (a) effects of different momentum dependencies of the CDF on scattering of projectiles on the electron subsystem are investigated. The ‘effective one-band’ approximation for target electrons produces good coincidence of the calculated electron mean free paths with those obtained in experiments in metals. (b) Effects of collective response of a lattice appeared to dominate in randomization of electron motion. We study how sensitive these effects are to the target temperature. We also compare results of applications of different model forms of (quasi-) elastic cross sections in simulations of the ion track kinetics, e.g. those calculated taking into account optical phonons in the CDF form vs. Mott’s atomic cross sections. (c) It is demonstrated that the kinetics of valence holes significantly affects redistribution of the excess electronic energy in the vicinity of an SHI trajectory as well as its conversion into lattice excitation in dielectrics and semiconductors. (d) It is also shown that induced transport of photons originated from radiative decay of core holes brings the excess energy faster and farther away from the track core, however, the amount of this energy is relatively small.

  14. Tunneling Characteristics of an Electron-Hole Trilayer in a Parallel Magnetic Field

    National Research Council Canada - National Science Library

    Lin, Y

    2003-01-01

    We have studied the tunneling properties of GaSb/AlSb/InAs/AlSb/GaSb heterostructures in which electrons- and boles accumulate in the InAs and GaSb regions respectively under a magnetic field parallel...

  15. Migration of O vacancies in α-quartz: The effect of excitons and electron holes

    International Nuclear Information System (INIS)

    Song, Jakyoung; Corrales, L. Rene; Kresse, Georg; Jonsson, Hannes

    2001-01-01

    We have used density-functional theory and the nudged elastic-band method to calculate migration pathways and estimated the activation energy for the diffusion of oxygen vacancies in α-quartz. While the energy barrier for the diffusion of a neutral vacancy is very high, 4.1 eV, the binding of a triplet-state exciton to the vacancy lowers the barrier to 1.7 eV and the attachment of a hole lowers the barrier to 1.9 eV, making the vacancy mobile at commonly used annealing temperatures

  16. Electrons, holes, and excitons in GaAs polytype quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Climente, Juan I.; Segarra, Carlos; Rajadell, Fernando; Planelles, Josep, E-mail: josep.planelles@uji.es [Departament de Química Física i Analítica, Universitat Jaume I, E-12080 Castelló (Spain)

    2016-03-28

    Single and multi-band k⋅p Hamiltonians for GaAs crystal phase quantum dots are used to assess ongoing experimental activity on the role of such factors as quantum confinement, spontaneous polarization, valence band mixing, and exciton Coulomb interaction. Spontaneous polarization is found to be a dominating term. Together with the control of dot thickness [Vainorius et al., Nano Lett. 15, 2652 (2015)], it enables wide exciton wavelength and lifetime tunability. Several new phenomena are predicted for small diameter dots [Loitsch et al., Adv. Mater. 27, 2195 (2015)], including non-heavy hole ground state, strong hole spin admixture, and a type-II to type-I exciton transition, which can be used to improve the absorption strength and reduce the radiative lifetime of GaAs polytypes.

  17. Dynamical Languages

    Science.gov (United States)

    Xie, Huimin

    The following sections are included: * Definition of Dynamical Languages * Distinct Excluded Blocks * Definition and Properties * L and L″ in Chomsky Hierarchy * A Natural Equivalence Relation * Symbolic Flows * Symbolic Flows and Dynamical Languages * Subshifts of Finite Type * Sofic Systems * Graphs and Dynamical Languages * Graphs and Shannon-Graphs * Transitive Languages * Topological Entropy

  18. Semiclassical dynamics

    International Nuclear Information System (INIS)

    Balazs, N.L.

    1979-01-01

    It is pointed out that in semiclassical dynamics one is encouraged to study the evolution of those curves in phase space which classically represent ensembles corresponding to wave functions. It is shown that the fixed points generate new time scales so that for times longer than the critical times, quantum dynamics will profoundly differ from classical dynamics. (P.L.)

  19. Charge-carrier dynamics and Coulomb effects in semiconductor tetrapods

    International Nuclear Information System (INIS)

    Mauser, Christian

    2011-01-01

    charge carriers were additionally studied at high excitation energies. An efficient multi-exciton emission of the CdSe/CdS tetrapods could be observed, which is to be lead back to the exciton phase-space filling and a reduced Auger effect. The larger volume of the longer tetrapods allows a dual emission from the CdSe and the CdS with comparable intensities. The occuring Coulomb effects between a spatially separated electron-hole pair were studied in CdSe/CdTe tetrapods, which exhibit a type-II transition. A correlation between the tetrapod leg length and the binding energy of the charge-transfer exciton could be established, which is also reproduced in the theoretical simulations.

  20. Lightwave-driven quasiparticle collisions on a subcycle timescale.

    Science.gov (United States)

    Langer, F; Hohenleutner, M; Schmid, C P; Poellmann, C; Nagler, P; Korn, T; Schüller, C; Sherwin, M S; Huttner, U; Steiner, J T; Koch, S W; Kira, M; Huber, R

    2016-05-12

    Ever since Ernest Rutherford scattered α-particles from gold foils, collision experiments have revealed insights into atoms, nuclei and elementary particles. In solids, many-body correlations lead to characteristic resonances--called quasiparticles--such as excitons, dropletons, polarons and Cooper pairs. The structure and dynamics of quasiparticles are important because they define macroscopic phenomena such as Mott insulating states, spontaneous spin- and charge-order, and high-temperature superconductivity. However, the extremely short lifetimes of these entities make practical implementations of a suitable collider challenging. Here we exploit lightwave-driven charge transport, the foundation of attosecond science, to explore ultrafast quasiparticle collisions directly in the time domain: a femtosecond optical pulse creates excitonic electron-hole pairs in the layered dichalcogenide tungsten diselenide while a strong terahertz field accelerates and collides the electrons with the holes. The underlying dynamics of the wave packets, including collision, pair annihilation, quantum interference and dephasing, are detected as light emission in high-order spectral sidebands of the optical excitation. A full quantum theory explains our observations microscopically. This approach enables collision experiments with various complex quasiparticles and suggests a promising new way of generating sub-femtosecond pulses.

  1. Discrete dynamics versus analytic dynamics

    DEFF Research Database (Denmark)

    Toxværd, Søren

    2014-01-01

    For discrete classical Molecular dynamics obtained by the “Verlet” algorithm (VA) with the time increment h there exists a shadow Hamiltonian H˜ with energy E˜(h) , for which the discrete particle positions lie on the analytic trajectories for H˜ . Here, we proof that there, independent...... of such an analytic analogy, exists an exact hidden energy invariance E * for VA dynamics. The fact that the discrete VA dynamics has the same invariances as Newtonian dynamics raises the question, which of the formulations that are correct, or alternatively, the most appropriate formulation of classical dynamics....... In this context the relation between the discrete VA dynamics and the (general) discrete dynamics investigated by Lee [Phys. Lett. B122, 217 (1983)] is presented and discussed....

  2. Ultrafast dynamics of Coulomb correlated excitons in GaAs quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Mycek, M.A. [Univ. of California, Berkeley, CA (United States). Dept. of Physics]|[Lawrence Berkeley National Lab., CA (United States). Materials Sciences Div.

    1995-12-01

    The author measures the transient nonlinear optical response of room temperature excitons in gallium arsenide quantum wells via multi-wave mixing experiments. The dynamics of the resonantly excited excitons is directly reflected by the ultrafast decay of the induced nonlinear polarization, which radiates the detected multi-wave mixing signal. She characterizes this ultrafast coherent emission in both amplitude and phase, using time- and frequency-domain measurement techniques, to better understand the role of Coulomb correlation in these systems. To interpret the experimental results, the nonlinear optical response of a dense medium is calculated using a model including Coulomb interaction. She contributes three new elements to previous theoretical and experimental studies of these systems. First, surpassing traditional time-integrated measurements, she temporally resolves the amplitude of the ultrafast coherent emission. Second, in addition to measuring the third-order four-wave mixing signal, she also investigates the fifth-order six-wave mixing response. Third, she characterizes the ultrafast phase dynamics of the nonlinear emission using interferometric techniques with an unprecedented resolution of approximately 140 attoseconds. The author finds that effects arising from Coulomb correlation dominate the nonlinear optical response when the density of excitons falls below 3 {times} 10{sup 11} cm{sup {minus}2}, the saturation density. These signatures of Coulomb correlation are investigated for increasing excitation density to gradually screen the interactions and test the validity of the model for dense media. The results are found to be qualitatively consistent with both the predictions of the model and with numerical solutions to the semiconductor Bloch equations. Importantly, the results also indicate current experimental and theoretical limitations, which should be addressed in future research.

  3. Femtosecond few- to single-electron point-projection microscopy for nanoscale dynamic imaging

    Directory of Open Access Journals (Sweden)

    A. R. Bainbridge

    2016-03-01

    Full Text Available Femtosecond electron microscopy produces real-space images of matter in a series of ultrafast snapshots. Pulses of electrons self-disperse under space-charge broadening, so without compression, the ideal operation mode is a single electron per pulse. Here, we demonstrate femtosecond single-electron point projection microscopy (fs-ePPM in a laser-pump fs-e-probe configuration. The electrons have an energy of only 150 eV and take tens of picoseconds to propagate to the object under study. Nonetheless, we achieve a temporal resolution with a standard deviation of 114 fs (equivalent to a full-width at half-maximum of 269 ± 40 fs combined with a spatial resolution of 100 nm, applied to a localized region of charge at the apex of a nanoscale metal tip induced by 30 fs 800 nm laser pulses at 50 kHz. These observations demonstrate real-space imaging of reversible processes, such as tracking charge distributions, is feasible whilst maintaining femtosecond resolution. Our findings could find application as a characterization method, which, depending on geometry, could resolve tens of femtoseconds and tens of nanometres. Dynamically imaging electric and magnetic fields and charge distributions on sub-micron length scales opens new avenues of ultrafast dynamics. Furthermore, through the use of active compression, such pulses are an ideal seed for few-femtosecond to attosecond imaging applications which will access sub-optical cycle processes in nanoplasmonics.

  4. Computational Benchmarking for Ultrafast Electron Dynamics: Wave Function Methods vs Density Functional Theory.

    Science.gov (United States)

    Oliveira, Micael J T; Mignolet, Benoit; Kus, Tomasz; Papadopoulos, Theodoros A; Remacle, F; Verstraete, Matthieu J

    2015-05-12

    Attosecond electron dynamics in small- and medium-sized molecules, induced by an ultrashort strong optical pulse, is studied computationally for a frozen nuclear geometry. The importance of exchange and correlation effects on the nonequilibrium electron dynamics induced by the interaction of the molecule with the strong optical pulse is analyzed by comparing the solution of the time-dependent Schrödinger equation based on the correlated field-free stationary electronic states computed with the equationof-motion coupled cluster singles and doubles and the complete active space multi-configurational self-consistent field methodologies on one hand, and various functionals in real-time time-dependent density functional theory (TDDFT) on the other. We aim to evaluate the performance of the latter approach, which is very widely used for nonlinear absorption processes and whose computational cost has a more favorable scaling with the system size. We focus on LiH as a toy model for a nontrivial molecule and show that our conclusions carry over to larger molecules, exemplified by ABCU (C10H19N). The molecules are probed with IR and UV pulses whose intensities are not strong enough to significantly ionize the system. By comparing the evolution of the time-dependent field-free electronic dipole moment, as well as its Fourier power spectrum, we show that TD-DFT performs qualitatively well in most cases. Contrary to previous studies, we find almost no changes in the TD-DFT excitation energies when excited states are populated. Transitions between states of different symmetries are induced using pulses polarized in different directions. We observe that the performance of TD-DFT does not depend on the symmetry of the states involved in the transition.

  5. Dynamics Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Dynamics Lab replicates vibration environments for every Navy platform. Testing performed includes: Flight Clearance, Component Improvement, Qualification, Life...

  6. Dynamical systems

    CERN Document Server

    Sternberg, Shlomo

    2010-01-01

    Celebrated mathematician Shlomo Sternberg, a pioneer in the field of dynamical systems, created this modern one-semester introduction to the subject for his classes at Harvard University. Its wide-ranging treatment covers one-dimensional dynamics, differential equations, random walks, iterated function systems, symbolic dynamics, and Markov chains. Supplementary materials offer a variety of online components, including PowerPoint lecture slides for professors and MATLAB exercises.""Even though there are many dynamical systems books on the market, this book is bound to become a classic. The the

  7. Dynamic Capabilities

    DEFF Research Database (Denmark)

    Grünbaum, Niels Nolsøe; Stenger, Marianne

    2013-01-01

    The findings reveal a positive relationship between dynamic capabilities and innovation performance in the case enterprises, as we would expect. It was, however, not possible to establish a positive relationship between innovation performance and profitability. Nor was there any positive...... relationship between dynamic capabilities and profitability....

  8. Cu-Ni nanowire-based TiO{sub 2} hybrid for the dynamic photodegradation of acetaldehyde gas pollutant under visible light

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Shuying [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049 (China); Xie, Xiaofeng, E-mail: xxfshcn@163.com [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Chen, Sheng-Chieh [College of Science and Engineering, University of Minnesota, Minneapolis, MN 55455 (United States); Tong, Shengrui [Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Lu, Guanhong [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Pui, David Y.H. [College of Science and Engineering, University of Minnesota, Minneapolis, MN 55455 (United States); Sun, Jing [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China)

    2017-06-30

    dynamic photocatalytic efficiency of TCN containing 3 wt% Cu-Ni NWs was about 88% and 56% (continuous 500 ppm CH{sub 3}CHO feeding, 20 SCCM) under UV and visible light, respectively. ESR results proved that the recombination of photo-generated electron-hole pairs was inhibited significantly in TCN nanocomposite. Finally, the mechanism for electron-hole pairs’ separation and transmission at Schottky barrier interface between Cu-Ni NWs and TiO{sub 2} layers has been proposed based on the above analyses.

  9. Relaxation processes in aqueous solutions upon X-ray exposure. Entanglement of electronic and nuclear dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Unger, Isaak

    2017-07-01

    About a decade ago new types of electronic non-radiative relaxation processes, involving the environment of an electronically excited or ionized monomer, have been predicted for van der Waals clusters and these were also the first systems where such processes have been detected experimentally. These new autoionization channels encompass the recombination of an electron and a hole, and the energy transfer to a neighboring atom or molecule. Two processes can be distinguished here. In the intermolecular Coulombic decay (ICD) the hole created upon ionization of a monomer is filled by a valence electron of the same species, and the energy released in this electron-hole recombination is used to ionize a neighboring species. In the electron transfer mediated decay (ETMD) the initial hole is filled by an electron from a neighboring species, and the energy released by this recombination is either used to ionize the same neighbor species, or to ionize a third monomer. In more recent experiments on liquid water it has been discovered that these non- local autoionization processes are strongly coupled with ultrafast nuclear dynamics. The core ionization initiates proton motion along a hydrogen donor-bond of the electronically excited water cation. This nuclear dynamics leads to the formation of transient cationic species where a proton is shared by two neighboring water molecules. Subsequent autoionization, either via Auger decay, ICD or ETMD, then occurs from any of such structure transients. This relaxation process is termed proton transfer mediated charge separation, PTM-CS. It has been found in a number of experiments that the probability of PTM-CS to occur depends on the hydrogen-bond strength between the core-ionized molecule and solvent molecules.

  10. Immense Magnetic Response of Exciplex Light Emission due to Correlated Spin-Charge Dynamics

    Science.gov (United States)

    Wang, Yifei; Sahin-Tiras, Kevser; Harmon, Nicholas J.; Wohlgenannt, Markus; Flatté, Michael E.

    2016-01-01

    As carriers slowly move through a disordered energy landscape in organic semiconductors, tiny spatial variations in spin dynamics relieve spin blocking at transport bottlenecks or in the electron-hole recombination process that produces light. Large room-temperature magnetic-field effects (MFEs) ensue in the conductivity and luminescence. Sources of variable spin dynamics generate much larger MFEs if their spatial structure is correlated on the nanoscale with the energetic sites governing conductivity or luminescence such as in coevaporated organic blends within which the electron resides on one molecule and the hole on the other (an exciplex). Here, we show that exciplex recombination in blends exhibiting thermally activated delayed fluorescence produces MFEs in excess of 60% at room temperature. In addition, effects greater than 4000% can be achieved by tuning the device's current-voltage response curve by device conditioning. Both of these immense MFEs are the largest reported values for their device type at room temperature. Our theory traces this MFE and its unusual temperature dependence to changes in spin mixing between triplet exciplexes and light-emitting singlet exciplexes. In contrast, spin mixing of excitons is energetically suppressed, and thus spin mixing produces comparatively weaker MFEs in materials emitting light from excitons by affecting the precursor pairs. Demonstration of immense MFEs in common organic blends provides a flexible and inexpensive pathway towards magnetic functionality and field sensitivity in current organic devices without patterning the constituent materials on the nanoscale. Magnetic fields increase the power efficiency of unconditioned devices by 30% at room temperature, also showing that magnetic fields may increase the efficiency of the thermally activated delayed fluorescence process.

  11. Immense Magnetic Response of Exciplex Light Emission due to Correlated Spin-Charge Dynamics

    Directory of Open Access Journals (Sweden)

    Yifei Wang

    2016-02-01

    Full Text Available As carriers slowly move through a disordered energy landscape in organic semiconductors, tiny spatial variations in spin dynamics relieve spin blocking at transport bottlenecks or in the electron-hole recombination process that produces light. Large room-temperature magnetic-field effects (MFEs ensue in the conductivity and luminescence. Sources of variable spin dynamics generate much larger MFEs if their spatial structure is correlated on the nanoscale with the energetic sites governing conductivity or luminescence such as in coevaporated organic blends within which the electron resides on one molecule and the hole on the other (an exciplex. Here, we show that exciplex recombination in blends exhibiting thermally activated delayed fluorescence produces MFEs in excess of 60% at room temperature. In addition, effects greater than 4000% can be achieved by tuning the device’s current-voltage response curve by device conditioning. Both of these immense MFEs are the largest reported values for their device type at room temperature. Our theory traces this MFE and its unusual temperature dependence to changes in spin mixing between triplet exciplexes and light-emitting singlet exciplexes. In contrast, spin mixing of excitons is energetically suppressed, and thus spin mixing produces comparatively weaker MFEs in materials emitting light from excitons by affecting the precursor pairs. Demonstration of immense MFEs in common organic blends provides a flexible and inexpensive pathway towards magnetic functionality and field sensitivity in current organic devices without patterning the constituent materials on the nanoscale. Magnetic fields increase the power efficiency of unconditioned devices by 30% at room temperature, also showing that magnetic fields may increase the efficiency of the thermally activated delayed fluorescence process.

  12. Jumping Dynamics

    DEFF Research Database (Denmark)

    Sannino, Francesco

    2013-01-01

    paradigm the physical scale and henceforth also the massive spectrum of the theory jump at the lower boundary of the conformal window. In particular we propose that a theory can suddenly jump from a Quantum Chromodynamics type spectrum, at the lower boundary of the conformal window, to a conformal one...... without particle interpretation. The jumping scenario, therefore, does not support a near-conformal dynamics of walking type. We will also discuss the impact of jumping dynamics on the construction of models of dynamical electroweak symmetry breaking....

  13. Galactic dynamics

    CERN Document Server

    Binney, James

    2008-01-01

    Since it was first published in 1987, Galactic Dynamics has become the most widely used advanced textbook on the structure and dynamics of galaxies and one of the most cited references in astrophysics. Now, in this extensively revised and updated edition, James Binney and Scott Tremaine describe the dramatic recent advances in this subject, making Galactic Dynamics the most authoritative introduction to galactic astrophysics available to advanced undergraduate students, graduate students, and researchers. Every part of the book has been thoroughly overhauled, and many section

  14. Space dynamics

    International Nuclear Information System (INIS)

    Corno, S.E.

    1995-01-01

    Analytical methods for Space Dynamics of fission reactors, are presented. It is shown how a few sample problems in space dynamics can be solved, within the one and two group diffusion model, by purely analytical tools, essentially based on Laplace transform and complex Green function techniques. A quite suggestive generalization of this approach, applicable to the fluid core reactors, whose fuel is undergoing a violent mixing, is reported and briefly discussed. (author)

  15. Structural Dynamics

    International Nuclear Information System (INIS)

    Kim, Du Gi

    2005-08-01

    This book introduces summary of structural dynamics, the reason of learning of structural dynamics, single-degree of freedom system, simple harmonic vibration and application, numerical analysis method, such as time domain and frequency domain and nonlinear system, multi-degree of freedom system random vibration over discrete distribution, continuous distribution and extreme value distribution, circumstance vibration, earth quake vibration, including input earthquake, and earthquake-resistant design and capacity spectrum method, wind oscillation wave vibration, vibration control and maintenance control.

  16. Double optical gating

    Science.gov (United States)

    Gilbertson, Steve

    The observation and control of dynamics in atomic and molecular targets requires the use of laser pulses with duration less than the characteristic timescale of the process which is to be manipulated. For electron dynamics, this time scale is on the order of attoseconds where 1 attosecond = 10 -18 seconds. In order to generate pulses on this time scale, different gating methods have been proposed. The idea is to extract or "gate" a single pulse from an attosecond pulse train and switch off all the other pulses. While previous methods have had some success, they are very difficult to implement and so far very few labs have access to these unique light sources. The purpose of this work is to introduce a new method, called double optical gating (DOG), and to demonstrate its effectiveness at generating high contrast single isolated attosecond pulses from multi-cycle lasers. First, the method is described in detail and is investigated in the spectral domain. The resulting attosecond pulses produced are then temporally characterized through attosecond streaking. A second method of gating, called generalized double optical gating (GDOG), is also introduced. This method allows attosecond pulse generation directly from a carrier-envelope phase un-stabilized laser system for the first time. Next the methods of DOG and GDOG are implemented in attosecond applications like high flux pulses and extreme broadband spectrum generation. Finally, the attosecond pulses themselves are used in experiments. First, an attosecond/femtosecond cross correlation is used for characterization of spatial and temporal properties of femtosecond pulses. Then, an attosecond pump, femtosecond probe experiment is conducted to observe and control electron dynamics in helium for the first time.

  17. Ultrafast High Harmonic, Soft X-Ray Probing of Molecular Dynamics

    Science.gov (United States)

    2009-12-16

    12. D. G. Lappas and A. L’Huillier, "Generation of attosecond XUV pulses in strong laser-atom interactions," Phys. Rev. A 58, 4140 (1998). 13...presentation at the 37 th AIAA/ASME/ SAE /ASEE Joint Propulsion Conference and Exhibition, Salt Lake City, UT, p. 3937 (2001). 36. A. Bultel, B. G

  18. Dynamic Bifurcations

    CERN Document Server

    1991-01-01

    Dynamical Bifurcation Theory is concerned with the phenomena that occur in one parameter families of dynamical systems (usually ordinary differential equations), when the parameter is a slowly varying function of time. During the last decade these phenomena were observed and studied by many mathematicians, both pure and applied, from eastern and western countries, using classical and nonstandard analysis. It is the purpose of this book to give an account of these developments. The first paper, by C. Lobry, is an introduction: the reader will find here an explanation of the problems and some easy examples; this paper also explains the role of each of the other paper within the volume and their relationship to one another. CONTENTS: C. Lobry: Dynamic Bifurcations.- T. Erneux, E.L. Reiss, L.J. Holden, M. Georgiou: Slow Passage through Bifurcation and Limit Points. Asymptotic Theory and Applications.- M. Canalis-Durand: Formal Expansion of van der Pol Equation Canard Solutions are Gevrey.- V. Gautheron, E. Isambe...

  19. Dynamic Pricing

    DEFF Research Database (Denmark)

    Sharifi, Reza; Anvari-Moghaddam, Amjad; Fathi, S. Hamid

    2017-01-01

    Dynamic pricing scheme, also known as real-time pricing (RTP), can be more efficient and technically beneficial than the other price-based schemes (such as flat-rate or time-of-use (TOU) pricing) for enabling demand response (DR) actions. Over the past few years, advantages of RTP-based schemes h...... of dynamic pricing can lead to increased willingness of consumers to participate in DR programs which in turn improve the operation of liberalized electricity markets.......Dynamic pricing scheme, also known as real-time pricing (RTP), can be more efficient and technically beneficial than the other price-based schemes (such as flat-rate or time-of-use (TOU) pricing) for enabling demand response (DR) actions. Over the past few years, advantages of RTP-based schemes...

  20. Record dynamics

    DEFF Research Database (Denmark)

    Robe, Dominic M.; Boettcher, Stefan; Sibani, Paolo

    2016-01-01

    When quenched rapidly beyond their glass transition, colloidal suspensions fall out of equilibrium. The pace of their dynamics then slows down with the system age, i.e., with the time elapsed after the quench. This breaking of time translational invariance is associated with dynamical observables...... which depend on two time-arguments. The phenomenology is shared by a broad class of aging systems and calls for an equally broad theoretical description. The key idea is that, independent of microscopic details, aging systems progress through rare intermittent structural relaxations that are de......-facto irreversible and become increasingly harder to achieve. Thus, a progression of record-sized dynamical barriers are traversed in the approach to equilibration. Accordingly, the statistics of the events is closely described by a log-Poisson process. Originally developed for relaxation in spin glasses...

  1. Exciton-relaxation dynamics in lead halides

    International Nuclear Information System (INIS)

    Iwanaga, Masanobu; Hayashi, Tetsusuke

    2003-01-01

    We survey recent comprehensive studies of exciton relaxation in the crystals of lead halides. The luminescence and electron-spin-resonance studies have revealed that excitons in lead bromide spontaneously dissociate and both electrons and holes get self-trapped individually. Similar relaxation has been also clarified in lead chloride. The electron-hole separation is ascribed to repulsive correlation via acoustic phonons. Besides, on the basis of the temperature profiles of self-trapped states, we discuss the origin of luminescence components which are mainly induced under one-photon excitation into the exciton band in lead fluoride, lead chloride, and lead bromide

  2. Dynamical systems

    CERN Document Server

    Birkhoff, George D

    1927-01-01

    His research in dynamics constitutes the middle period of Birkhoff's scientific career, that of maturity and greatest power. -Yearbook of the American Philosophical Society The author's great book€¦is well known to all, and the diverse active modern developments in mathematics which have been inspired by this volume bear the most eloquent testimony to its quality and influence. -Zentralblatt MATH In 1927, G. D. Birkhoff wrote a remarkable treatise on the theory of dynamical systems that would inspire many later mathematicians to do great work. To a large extent, Birkhoff was writing about his o

  3. Glassy Dynamics

    DEFF Research Database (Denmark)

    Jensen, Henrik J.; Sibani, Paolo

    2007-01-01

    The term glassy dynamics is often used to refer to the extremely slow relaxation observed in several types of many component systems. The time span needed to reach a steady, time independent, state will typically be far beyond experimentally accessible time scales. When melted alloys are cooled...... down they typically do not enter a crystalline ordered state. Instead the atoms retain the amorphous arrangement characteristic of the liquid high temperature phase while the mobility of the molecules decreases very many orders of magnitude. This colossal change in the characteristic dynamical time...

  4. Forest dynamics.

    Science.gov (United States)

    Frelich, Lee

    2016-01-01

    Forest dynamics encompass changes in stand structure, species composition, and species interactions with disturbance and environment over a range of spatial and temporal scales. For convenience, spatial scale is defined as individual tree, neighborhood, stand, and landscape. Whether a given canopy-leveling disturbance will initiate a sequence of development in structure with little change in composition or initiate an episode of succession depends on a match or mismatch, respectively, with traits of the dominant tree species that allow the species to survive disturbance. When these match, certain species-disturbance type combinations lock in a pattern of stand and landscape dynamics that can persist for several generations of trees; thus, dominant tree species regulate, as well as respond to, disturbance. A complex interaction among tree species, neighborhood effects, disturbance type and severity, landform, and soils determines how stands of differing composition form and the mosaic of stands that compose the landscape. Neighborhood effects (e.g., serotinous seed rain, sprouting, shading, leaf-litter chemistry, and leaf-litter physical properties) operate at small spatial extents of the individual tree and its neighbors but play a central role in forest dynamics by contributing to patch formation at stand scales and dynamics of the entire landscape. Dominance by tree species with neutral to negative neighborhood effects leads to unstable landscape dynamics in disturbance-prone regions, wherein most stands are undergoing succession; stability can only occur under very low-severity disturbance regimes. Dominance by species with positive effects leads to stable landscape dynamics wherein only a small proportion of stands undergo succession at any one time. Positive neighborhood effects are common in temperate and boreal zones, whereas negative effects are more common in tropical climates. Landscapes with positive dynamics have alternate categories of dynamics

  5. Classical dynamics

    CERN Document Server

    Greenwood, Donald T

    1997-01-01

    Graduate-level text for science and technology students provides strong background in the more abstract and intellectually satisfying areas of dynamical theory. Topics include d'Alembert's principle and the idea of virtual work, Hamilton's equations, Hamilton-Jacobi theory, canonical transformations, more. Problems and references at chapter ends.

  6. Expansion dynamics

    International Nuclear Information System (INIS)

    Knoll, J.

    1985-10-01

    A quantum dynamical model is suggested which describes the expansion and disassembly phase of highly excited compounds formed in energetic heavy-ion collisions. First applications in two space and one time dimensional model world are discussed and qualitatively compared to standard freeze-out concepts. (orig.)

  7. Membrane dynamics

    DEFF Research Database (Denmark)

    Bendix, Pól Martin

    2015-01-01

    Current topics include membrane-protein interactions with regard to membrane deformation or curvature sensing by BAR domains. Also, we study the dynamics of membrane tubes of both cells and simple model membrane tubes. Finally, we study membrane phase behavior which has important implications...... for the lateral organization of membranes as wells as for physical properties like bending, permeability and elasticity...

  8. Random dynamics

    International Nuclear Information System (INIS)

    Bennett, D.L.; Brene, N.; Nielsen, H.B.

    1986-06-01

    The goal of random dynamics is the derivation of the laws of Nature as we know them (standard model) from inessential assumptions. The inessential assumptions made here are expressed as sets of general models at extremely high energies: gauge glass and spacetime foam. Both sets of models lead tentatively to the standard model. (orig.)

  9. Dynamic LIMIDS

    NARCIS (Netherlands)

    Díez, F.J.; Gerven, M.A.J. van; Sucar, L.E.; Morales, E.F.; Hoey, J.

    2011-01-01

    One of the objectives of artificial intelligence is to build decision-support models for systems that evolve over time and include several types of uncertainty. Dynamic limited-memory influence diagrams (DLIMIDs) are a new type of model proposed recently for this kind of problems. DLIMIDs are

  10. System Dynamics

    Science.gov (United States)

    Morecroft, John

    System dynamics is an approach for thinking about and simulating situations and organisations of all kinds and sizes by visualising how the elements fit together, interact and change over time. This chapter, written by John Morecroft, describes modern system dynamics which retains the fundamentals developed in the 1950s by Jay W. Forrester of the MIT Sloan School of Management. It looks at feedback loops and time delays that affect system behaviour in a non-linear way, and illustrates how dynamic behaviour depends upon feedback loop structures. It also recognises improvements as part of the ongoing process of managing a situation in order to achieve goals. Significantly it recognises the importance of context, and practitioner skills. Feedback systems thinking views problems and solutions as being intertwined. The main concepts and tools: feedback structure and behaviour, causal loop diagrams, dynamics, are practically illustrated in a wide variety of contexts from a hot water shower through to a symphony orchestra and the practical application of the approach is described through several real examples of its use for strategic planning and evaluation.

  11. Coastal Dynamics

    NARCIS (Netherlands)

    Roelvink, J.A.; Steetzel, H.J.; Bliek, A.; Rakhorst, H.D.; Roelse, P.; Bakker, W.T.

    1998-01-01

    This book deals on "Coastal Dynamics", which will be defined in a narrow sense as a mathematical theory, which starts from given equations of motion for the sediment, which leads with the continuity equation and given boundary conditions to a calculated (eventually schematized) coastal topography,

  12. Structural dynamics

    CERN Document Server

    Strømmen, Einar N

    2014-01-01

    This book introduces to the theory of structural dynamics, with focus on civil engineering structures that may be described by line-like beam or beam-column type of systems, or by a system of rectangular plates. Throughout this book the mathematical presentation contains a classical analytical description as well as a description in a discrete finite element format, covering the mathematical development from basic assumptions to the final equations ready for practical dynamic response predictions. Solutions are presented in time domain as well as in frequency domain. Structural Dynamics starts off at a basic level and step by step brings the reader up to a level where the necessary safety considerations to wind or horizontal ground motion induced dynamic design problems can be performed. The special theory of the tuned mass damper has been given a comprehensive treatment, as this is a theory not fully covered elsewhere. For the same reason a chapter on the problem of moving loads on beams has been included.

  13. Random dynamics

    International Nuclear Information System (INIS)

    Bennett, D.L.

    1987-01-01

    The goal of random dynamics is the derivation of the laws of Nature as we know them (standard model) from inessential assumptions. The inessential assumptions made here are expressed as sets of general models at extremely high energies: Gauge glass and spacetime foam. Both sets of models lead tentatively to the standard model. (orig.)

  14. Random Dynamics

    Science.gov (United States)

    Bennett, D. L.; Brene, N.; Nielsen, H. B.

    1987-01-01

    The goal of random dynamics is the derivation of the laws of Nature as we know them (standard model) from inessential assumptions. The inessential assumptions made here are expressed as sets of general models at extremely high energies: gauge glass and spacetime foam. Both sets of models lead tentatively to the standard model.

  15. Applied dynamics

    CERN Document Server

    Schiehlen, Werner

    2014-01-01

    Applied Dynamics is an important branch of engineering mechanics widely applied to mechanical and automotive engineering, aerospace and biomechanics as well as control engineering and mechatronics. The computational methods presented are based on common fundamentals. For this purpose analytical mechanics turns out to be very useful where D’Alembert’s principle in the Lagrangian formulation proves to be most efficient. The method of multibody systems, finite element systems and continuous systems are treated consistently. Thus, students get a much better understanding of dynamical phenomena, and engineers in design and development departments using computer codes may check the results more easily by choosing models of different complexity for vibration and stress analysis.

  16. Delta Dynamics

    DEFF Research Database (Denmark)

    Bendixen, Mette

    . The warming air temperature affects the soil temperature and permafrost thaws and destabilizes the material in the coastal zone. In Greenland, the warming temperature lowers the surface mass balance of the Greenland Ice Sheet and more material is transported to the coastal zone. The sea ice extent is thinning...... of a fjord and the second type is a wider fan-shaped open delta. Most deltas are directly coupled to the Greenland Ice Sheet or local icecaps and are highly influenced by the dynamics in the catchments. It is demonstrated how a modern changing climate directly affects delta dynamics, and that Greenlandic...... deltas are prograding, contrary to the global trend showing eroding Arctic coasts. Moreover, it is revealed that the increasing proglacial freshwater runoff, caused by a lowering of the surface mass balance of the Greenland Ice Sheet is the main determining agent in delta progradation. The final part...

  17. Fluid dynamics

    CERN Document Server

    Bernard, Peter S

    2015-01-01

    This book presents a focused, readable account of the principal physical and mathematical ideas at the heart of fluid dynamics. Graduate students in engineering, applied math, and physics who are taking their first graduate course in fluids will find this book invaluable in providing the background in physics and mathematics necessary to pursue advanced study. The book includes a detailed derivation of the Navier-Stokes and energy equations, followed by many examples of their use in studying the dynamics of fluid flows. Modern tensor analysis is used to simplify the mathematical derivations, thus allowing a clearer view of the physics. Peter Bernard also covers the motivation behind many fundamental concepts such as Bernoulli's equation and the stream function. Many exercises are designed with a view toward using MATLAB or its equivalent to simplify and extend the analysis of fluid motion including developing flow simulations based on techniques described in the book.

  18. Superconductor Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Gömöry, F [Bratislava, Inst. Elect. Eng. (Slovakia)

    2014-07-01

    Superconductors used in magnet technology could carry extreme currents because of their ability to keep the magnetic flux motionless. The dynamics of the magnetic flux interaction with superconductors is controlled by this property. The cases of electrical transport in a round wire and the magnetization of wires of various shapes (circular, elliptical, plate) in an external magnetic field are analysed. Resistance to the magnetic field penetration means that the field produced by the superconducting magnet is no longer proportional to the supplied current. It also leads to a dissipation of electromagnetic energy. In conductors with unequal transverse dimensions, such as flat cables, the orientation with respect to the magnetic field plays an essential role. A reduction of magnetization currents can be achieved by splitting the core of a superconducting wire into fine filaments; however, new kinds of electrical currents that couple the filaments consequently appear. Basic formulas allowing qualitative analyses of various flux dynamic cases are presented.

  19. Beam dynamics

    International Nuclear Information System (INIS)

    Abell, D; Adelmann, A; Amundson, J; Dragt, A; Mottershead, C; Neri, F; Pogorelov, I; Qiang, J; Ryne, R; Shalf, J; Siegerist, C; Spentzouris, P; Stern, E; Venturini, M; Walstrom, P

    2006-01-01

    We describe some of the accomplishments of the Beam Dynamics portion of the SciDAC Accelerator Science and Technology project. During the course of the project, our beam dynamics software has evolved from the era of different codes for each physical effect to the era of hybrid codes combining start-of-the-art implementations for multiple physical effects to the beginning of the era of true multi-physics frameworks. We describe some of the infrastructure that has been developed over the course of the project and advanced features of the most recent developments, the interplay betwen beam studies and simulations and applications to current machines at Fermilab. Finally we discuss current and future plans for simulations of the International Linear Collider

  20. Exciton dynamics in GaAs/AlxGa1-xAs quantum wells

    DEFF Research Database (Denmark)

    Litvinenko, K.; Birkedal, Dan; Lyssenko, V. G.

    1999-01-01

    The changes induced in the optical absorption spectrum of a GaAs/AlxGa1-xAs multiple quantum well due to a photoexcited carrier distribution are reexamined. We use a femtosecond pump-probe technique to excite excitons and free electron-hole pairs. We find that for densities up to 10(11) cm(-2...

  1. Dissociative photoionization of molecular hydrogen. A joint experimental and theoretical study of the electron-electron correlations induced by XUV photoionization and nuclear dynamics on IR-laser dressed transition states

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, Andreas

    2015-01-13

    In this thesis, the dissociative single-ionization of molecular hydrogen is investigated in a kinematically complete experiment by employing extreme ultraviolet attosecond pulse trains and infrared femtosecond laser pulses. Induced by the absorption of a single XUV photon, a pronounced energy-dependent asymmetry of the relative emission direction of the photoelectron and the ion is observed. The asymmetry pattern is explained in terms of an interference of two ionization pathways involving a doubly-excited state. This interpretation is validated by a semi-classical model which only takes the nuclear motion into account. Using this model and the observed asymmetry, it is furthermore possible to disentangle the two dissociation pathways which allows for the determination of the autoionization lifetime of the contributing doubly-excited state as a function of the internuclear distance. Moreover, using a pump-probe experiment the dissociation dynamics of molecular hydrogen is investigated. A time-delay dependent momentum distribution of the fragments is observed. With a combined quantum mechanical and semi-classical approach the mechanism giving rise to the observed time-dependence is identified in terms of an intuitive elevator mechanism.

  2. Hamiltonian dynamics

    CERN Document Server

    Vilasi, Gaetano

    2001-01-01

    This is both a textbook and a monograph. It is partially based on a two-semester course, held by the author for third-year students in physics and mathematics at the University of Salerno, on analytical mechanics, differential geometry, symplectic manifolds and integrable systems. As a textbook, it provides a systematic and self-consistent formulation of Hamiltonian dynamics both in a rigorous coordinate language and in the modern language of differential geometry. It also presents powerful mathematical methods of theoretical physics, especially in gauge theories and general relativity. As a m

  3. Complex dynamics

    CERN Document Server

    Carleson, Lennart

    1993-01-01

    Complex dynamics is today very much a focus of interest. Though several fine expository articles were available, by P. Blanchard and by M. Yu. Lyubich in particular, until recently there was no single source where students could find the material with proofs. For anyone in our position, gathering and organizing the material required a great deal of work going through preprints and papers and in some cases even finding a proof. We hope that the results of our efforts will be of help to others who plan to learn about complex dynamics and perhaps even lecture. Meanwhile books in the field a. re beginning to appear. The Stony Brook course notes of J. Milnor were particularly welcome and useful. Still we hope that our special emphasis on the analytic side will satisfy a need. This book is a revised and expanded version of notes based on lectures of the first author at UCLA over several \\Vinter Quarters, particularly 1986 and 1990. We owe Chris Bishop a great deal of gratitude for supervising the production of cour...

  4. Population dynamics

    Directory of Open Access Journals (Sweden)

    Cooch, E. G.

    2004-06-01

    Full Text Available Increases or decreases in the size of populations over space and time are, arguably, the motivation for much of pure and applied ecological research. The fundamental model for the dynamics of any population is straightforward: the net change over time in the abundance of some population is the simple difference between the number of additions (individuals entering the population minus the number of subtractions (individuals leaving the population. Of course, the precise nature of the pattern and process of these additions and subtractions is often complex, and population biology is often replete with fairly dense mathematical representations of both processes. While there is no doubt that analysis of such abstract descriptions of populations has been of considerable value in advancing our, there has often existed a palpable discomfort when the ‘beautiful math’ is faced with the often ‘ugly realities’ of empirical data. In some cases, this attempted merger is abandoned altogether, because of the paucity of ‘good empirical data’ with which the theoretician can modify and evaluate more conceptually–based models. In some cases, the lack of ‘data’ is more accurately represented as a lack of robust estimates of one or more parameters. It is in this arena that methods developed to analyze multiple encounter data from individually marked organisms has seen perhaps the greatest advances. These methods have rapidly evolved to facilitate not only estimation of one or more vital rates, critical to population modeling and analysis, but also to allow for direct estimation of both the dynamics of populations (e.g., Pradel, 1996, and factors influencing those dynamics (e.g., Nichols et al., 2000. The interconnections between the various vital rates, their estimation, and incorporation into models, was the general subject of our plenary presentation by Hal Caswell (Caswell & Fujiwara, 2004. Caswell notes that although interest has traditionally

  5. Spin dynamics in GaAs and (110)-GaAs heterostructures; Spindynamik in GaAs und (110)-GaAs-Heterostrukturen

    Energy Technology Data Exchange (ETDEWEB)

    Oertel, Stefan

    2012-07-01

    specially designed (110)-GaAs heterostructure consisting of a 9 nm thick quantum well separated by 3 nm thin AlGaAs barriers from two adjacent 4 nm quantum wells is characterized: The electron spin polarization in the 9 nm drain quantum well is measured in dependence on the energy of the circular optical injection. At the indirect optical injection via the heavy hole resonance of the thin quantum wells an electron spin polarization of 75% in the drain quantum well is reached. By means of the structure the impact of interface roughnesses in the 9 nm quantum well on the carrier dynamics is additionally investigated. The (110)-GaAs heterostructure is used to determine the spin relaxation time in (110)-GaAs quantum wells experimentally over a wide range of densities and temperatures. The special growth direction of the structure provides access to spin relaxation mechanisms that are usually concealed by the dominating Dyakonov-Perel mechanism. The measured elect ron spin relaxation times are interpreted as an exciton marker within the electron-hole plasma and are in good agreement with a simple model based upon the exciton fraction within the electron-hole plasma.

  6. Bile dynamics

    International Nuclear Information System (INIS)

    Harding, L.K.; Donovan, I.A.

    1986-01-01

    The availability of new biliary radiopharamaceutical led to the expectation that the physiology and the pathophysiology of bile would be resolved. Some aspects of the physiology of bile have clarified and it has been shown that nasogastric intubation does not cause bile reflux. Careful analysis of excretion patterns has allowed detection of obstruction of the bile duct after cholecystectomy, and the radiopharmaceuticals have proved helpful in the diagnosis of acute colecystitis. In chronic cholecystitis, however, varying results have been obtained. Information on the incidence and amount of reflux in normal subjects is also confused, since several different techniques have been used with widely varying results. The clinical value of biliary dynamic studies is at present limited in patients with chronic cholecystitis, peptic ulcer, or symptoms suggestive of bile reflux. More data, with appropriate control subjects, is required to identify abnormal reflux, determine its effects, and decide on appropriate treatment

  7. Group dynamics.

    Science.gov (United States)

    Scandiffio, A L

    1990-12-01

    Group dynamics play a significant role within any organization, culture, or unit. The important thing to remember with any of these structures is that they are made up of people--people with different ideas, motivations, background, and sometimes different agendas. Most groups, formal or informal, look for a leader in an effort to maintain cohesiveness of the unit. At times, that cultural bond must be developed; once developed, it must be nurtured. There are also times that one of the group no longer finds the culture comfortable and begins to act out behaviorally. It is these times that become trying for the leader as she or he attempts to remain objective when that which was once in the building phase of group cohesiveness starts to fall apart. At all times, the manager must continue to view the employee creating the disturbance as an integral part of the group. It is at this time that it is beneficial to perceive the employee exhibiting problem behaviors as a special employee, as one who needs the benefit of your experience and skills, as one who is still part of the group. It is also during this time that the manager should focus upon her or his own views in the area of power, communication, and the corporate culture of the unit that one has established before attempting to understand another's point of view. Once we understand our own motivation and accept ourselves, it is then that we may move on to offer assistance to another. Once we understand our insecurities recognizing staff dysfunction as a symptom of system dysfunction will not be so threatening to the concept of the manager that we perceive ourselves to be. It takes a secure person to admit that she or he favors staff before deciding to do something to change things. The important thing to know is that it can be done. The favored staff can find a new way of relating to others, the special employee can find new modes of behavior (and even find self-esteem in the process), the group can find new ways

  8. Fluid dynamics

    CERN Document Server

    Ruban, Anatoly I

    This is the first book in a four-part series designed to give a comprehensive and coherent description of Fluid Dynamics, starting with chapters on classical theory suitable for an introductory undergraduate lecture course, and then progressing through more advanced material up to the level of modern research in the field. The present Part 1 consists of four chapters. Chapter 1 begins with a discussion of Continuum Hypothesis, which is followed by an introduction to macroscopic functions, the velocity vector, pressure, density, and enthalpy. We then analyse the forces acting inside a fluid, and deduce the Navier-Stokes equations for incompressible and compressible fluids in Cartesian and curvilinear coordinates. In Chapter 2 we study the properties of a number of flows that are presented by the so-called exact solutions of the Navier-Stokes equations, including the Couette flow between two parallel plates, Hagen-Poiseuille flow through a pipe, and Karman flow above an infinite rotating disk. Chapter 3 is d...

  9. Internet dynamics

    Science.gov (United States)

    Lukose, Rajan Mathew

    The World Wide Web and the Internet are rapidly expanding spaces, of great economic and social significance, which offer an opportunity to study many phenomena, often previously inaccessible, on an unprecedented scale and resolution with relative ease. These phenomena are measurable on the scale of tens of millions of users and hundreds of millions of pages. By virtue of nearly complete electronic mediation, it is possible in principle to observe the time and ``spatial'' evolution of nearly all choices and interactions. This cyber-space therefore provides a view into a number of traditional research questions (from many academic disciplines) and creates its own new phenomena accessible for study. Despite its largely self-organized and dynamic nature, a number of robust quantitative regularities are found in the aggregate statistics of interesting and useful quantities. These regularities can be understood with the help of models that draw on ideas from statistical physics as well as other fields such as economics, psychology and decision theory. This thesis develops models that can account for regularities found in the statistics of Internet congestion and user surfing patterns and discusses some practical consequences. practical consequences.

  10. PREFACE: Dynamics of low-dimensional systems Dynamics of low-dimensional systems

    Science.gov (United States)

    Bernasconi, M.; Miret-Artés, S.; Toennies, J. P.

    2012-03-01

    With the development of techniques for high-resolution inelastic helium atom scattering (HAS), electron scattering (EELS) and neutron spin echo spectroscopy, it has become possible, within approximately the last thirty years, to measure the dispersion curves of surface phonons in insulators, semiconductors and metals. In recent years, the advent of new experimental techniques such as 3He spin-echo spectroscopy, scanning inelastic electron tunnel spectroscopy, inelastic x-ray scattering spectroscopy and inelastic photoemission have extended surface phonon spectroscopy to a variety of systems. These include ultra-thin metal films, adsorbates at surface and elementary processes where surface phonons play an important role. Other important directions have been actively pursued in the past decade: the dynamics of stepped surfaces and clusters grown on metal surfaces, due to their relevance in many dynamical and chemical processes at surfaces, including heterogeneous catalysis; clusters; diffusion etc. The role of surface effects in these processes has been conjectured since the early days of surface dynamics, although only now is the availability of ab initio approaches providing those conjectures with a microscopic basis. Last but not least, the investigation of non-adiabatic effects, originating for instance from the hybridization (avoided crossing) of the surface phonons branches with the quasi 1D electron-hole excitation branch, is also a challenging new direction. Furthermore, other elementary oscillations such as surface plasmons are being actively investigated. The aforementioned experimental breakthroughs have been accompanied by advances in the theoretical study of atom-surface interaction. In particular, in the past decade first principles calculations based on density functional perturbation theory have boosted the theoretical study of the dynamics of low-dimensional systems. Phonon dispersion relations of clean surfaces, the dynamics of adsorbates, and the

  11. First-principles calculation of optical absorption spectra in conjugated polymers: Role of electron-hole interaction

    International Nuclear Information System (INIS)

    Rohlfing, Michael; Tiago, M.L.; Louie, Steven G.

    2000-01-01

    Experimental and theoretical studies have shown that excitonic effects play an important role in the optical properties of conjugated polymers. The optical absorption spectrum of trans-polyacetylene, for example, can be understood as completely dominated by the formation of exciton bound states. We review a recently developed first-principles method for computing the excitonic effects and optical spectrum, with no adjustable parameters. This theory is used to study the absorption spectrum of two conjugated polymers: trans-polyacetylene and poly-phenylene-vinylene(PPV)

  12. Exploring excitonic signal in optical conductivity of ZnO through first-order electron-hole vertex correction

    Science.gov (United States)

    Khoirunnisa, Humaira; Aziz Majidi, Muhammad

    2018-04-01

    The emergence of exitonic signal in the optical response of a wide band-gap semiconductor has been a common knowledge in physics. There have been numerous experimental studies exploring the important role of excitons on influencing both the transport and optical properties of the materials. Despite the existence of much information on excitonic effects, there has not been much literature that explores detailed theoretical explanation on how the exitonic signal appears and how it evolves with temperature. Here, we propose a theoretical study on the optical conductivity of ZnO, a well-known wide band-gap semiconductor that we choose as a case study. ZnO has been known to exhibit excitonic states in its optical spectra in the energy range of ∼3.13-3.41 eV, with a high exciton binding energy of ∼60 meV. An experimental study on ZnO in 2014 revealed such a signal in its optical conductivity spectrum. We present a theoretical investigation on the appearance of excitonic signal in optical conductivity of ZnO. We model the wurtzite ZnO within an 8-band k.p approximation. We calculate the optical conductivity by incorporating the first-order vertex correction derived from the Feynman diagrams. Our calculation up to the first-order correction spectrum qualitatively confirms the existence of excitons in wurtzite ZnO.

  13. Proposed Quenching of Phonon-Induced Processes in Photoexcited Quantum Dots due to Electron-Hole Asymmetries

    DEFF Research Database (Denmark)

    Nysteen, Anders; Nielsen, Per Kær; Mørk, Jesper

    2013-01-01

    by photoluminescence excitation spectroscopy of a single quantum dot. We also investigate the implications for cavity QED, i.e., a coupled quantum dot-cavity system, and demonstrate that the phonon scattering may be strongly quenched. The quenching is explained by a balancing between the deformation potential...

  14. Picosecond kinetics of the electron-hole layers formation in wide-bandgap II-VI type-II heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Filatov, E.V.; Zaitsev, S.V.; Tartakovskii, I.I.; Maksimov, A.A. [Institute of Solid State Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow region (Russian Federation); Yakovlev, D.R. [A.F. Ioffe Physico-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Experimentelle Physik II, Technische Universitaet Dortmund (Germany); Waag, A. [Institute of Semiconductor Technology, Braunschweig Technical University, 38106 Braunschweig (Germany)

    2010-06-15

    Considerable slowdown of luminescence kinetics of the direct optical transition was discovered in ZnSe/BeTe type-II heterostructures under high levels of optical pumping. The effect is attributed to forming of a potential barrier for holes in the ZnSe layer due to band bending at high densities of spatially separated carriers. That results in a longer time of the photoexcited holes energy relaxation to their ground state in the BeTe layer. The decrease of overlapping of electron and hole wavefunctions in the ZnSe layer in thick ZnSe/BeTe structures at high levels of optical excitation reveals an additional important effect, that leads to sufficient retardation of radiative recombination time for photoexcited carriers (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Effects of electron-hole generation, transport and trapping in MOSFETs due to γ-ray exposure

    International Nuclear Information System (INIS)

    Soliman, F.A.S.; Al-Kabbani, A.S.S.

    1995-01-01

    Ionizing radiation has been found to seriously change the electrical properties of solid-state devices, leading to possible systems failure. The ionizing radiation effects on different n-and p-channel MOSFETs have been studied, where the failure mechanism is found to be mainly due to changes in oxide properties and surface effects which occur in the gate oxide and, or, field/oxide regions. As a result, the threshold voltage of the n-channel transistor was shifted from 1.10 to 2.65 V, while the channel mobility for both the n- and p-channel transistors decreases from 4500 and 3100 to 2000 and 1000 m 2 /V·, respectively. Besides, the transconductance drops from 610, 500 and 380 down to 51, 35 and 150 mS for the MFE 201 (n-channel), 3N128 (n-channel) and 3N163 (p-channel) transistors, respectively. Also, the net effect of charge trapping can also be seen as a random, stochastical process represented by global noise parameters. Finally, the gain and noise parameters have been investigated as a function of γ-dose. (Author)

  16. First-principles calculation of optical absorption spectra in conjugated polymers: Role of electron-hole interaction

    Energy Technology Data Exchange (ETDEWEB)

    Rohlfing, Michael; Tiago, M.L.; Louie, Steven G.

    2000-03-20

    Experimental and theoretical studies have shown that excitonic effects play an important role in the optical properties of conjugated polymers. The optical absorption spectrum of trans-polyacetylene, for example, can be understood as completely dominated by the formation of exciton bound states. We review a recently developed first-principles method for computing the excitonic effects and optical spectrum, with no adjustable parameters. This theory is used to study the absorption spectrum of two conjugated polymers: trans-polyacetylene and poly-phenylene-vinylene(PPV).

  17. Efficient and colour-stable hybrid white organic light-emitting diodes utilizing electron-hole balanced spacers

    Energy Technology Data Exchange (ETDEWEB)

    Leem, Dong-Seok; Kim, Ji Whan; Kim, Jang-Joo [Department of Materials Science and Engineering, and OLED Center, Seoul National University, Seoul 151-744 (Korea, Republic of); Jung, Sung Ouk; Kim, Seul-Ong; Kwon, Soon-Ki [School of Materials Science and Engineering, and Engineering Research Institute (ERI), Gyeongsang National University, Jinju 660-701 (Korea, Republic of); Kim, Se Hoon; Kim, Kee Young [Dongwoo Fine-Chem Co., Ltd, Pyeongtaek 451-822 (Korea, Republic of); Kim, Yun-Hi, E-mail: jjkim@snu.ac.k, E-mail: skwon@gnu.ac.k [Department of Chemistry and RINS, Gyeongsang National University, Jinju 660-701 (Korea, Republic of)

    2010-10-13

    High-efficiency two-colour white organic light-emitting diodes (WOLEDs) comprising a newly synthesized iridium complex orange phosphor ((impy){sub 2}Ir(acac)) and a blue fluorophor (BD012) have been realized by placing several kinds of thin spacers between two emitters. Hybrid WOLEDs with a spacer composed of a hole-transporting N,N-dicarbazolyl-3,5-benzene (mCP) and an electron-transporting 4,7-diphenyl-1,10-phenanthroline (Bphen) exhibit a high external quantum efficiency (EQE) of up to 8.4% and a negligible colour change (the colour coordinate of (0.39, 0.41) at 1000 cd m{sup -2}) with increasing brightness, whereas the device using a hole-transporting mCP spacer shows a relatively low EQE of 6.2% and a large shift of emitting colour with increasing brightness. Device performance is further characterized based on the charge transport behaviour of the spacers inserted between the two emitters.

  18. Efficient and colour-stable hybrid white organic light-emitting diodes utilizing electron-hole balanced spacers

    International Nuclear Information System (INIS)

    Leem, Dong-Seok; Kim, Ji Whan; Kim, Jang-Joo; Jung, Sung Ouk; Kim, Seul-Ong; Kwon, Soon-Ki; Kim, Se Hoon; Kim, Kee Young; Kim, Yun-Hi

    2010-01-01

    High-efficiency two-colour white organic light-emitting diodes (WOLEDs) comprising a newly synthesized iridium complex orange phosphor ((impy) 2 Ir(acac)) and a blue fluorophor (BD012) have been realized by placing several kinds of thin spacers between two emitters. Hybrid WOLEDs with a spacer composed of a hole-transporting N,N-dicarbazolyl-3,5-benzene (mCP) and an electron-transporting 4,7-diphenyl-1,10-phenanthroline (Bphen) exhibit a high external quantum efficiency (EQE) of up to 8.4% and a negligible colour change (the colour coordinate of (0.39, 0.41) at 1000 cd m -2 ) with increasing brightness, whereas the device using a hole-transporting mCP spacer shows a relatively low EQE of 6.2% and a large shift of emitting colour with increasing brightness. Device performance is further characterized based on the charge transport behaviour of the spacers inserted between the two emitters.

  19. Ionization and recombination in attosecond electric field pulses

    International Nuclear Information System (INIS)

    Dimitrovski, Darko; Solov'ev, Eugene A.; Briggs, John S.

    2005-01-01

    Based on the results of a previous communication [Dimitrovski et al., Phys. Rev. Lett. 93, 083003 (2004)], we study ionization and excitation of a hydrogenic atom from the ground and first excited states in short electric field pulses of several cycles. A process of ionization and recombination which occurs periodically in time is identified, for both small and extremely large peak electric field strengths. In the limit of large electric peak fields closed-form analytic expressions for the population of the initial state after single- and few-cycle pulses are derived. These formulas, strictly valid for asymptotically large momentum transfer from the field, give excellent agreement with fully numerical calculations for all momentum transfers

  20. Generation of high harmonics and attosecond pulses with ultrashort ...

    Indian Academy of Sciences (India)

    2014-07-11

    Jul 11, 2014 ... Two aspects of ultrashort pulse filaments are specifically discussed: (i) numerical simulation results on pulse self-compression by filamentation in a gas cell filled with noble gas. Measurements of high harmonics generated by the pulse extracted from the filament allows for the detection of intensity spikes ...

  1. Atomic Cluster Ionization and Attosecond Generation at Long Wavelengths

    Science.gov (United States)

    2015-10-31

    fellowships for further studies in science, mathematics, engineering or technology fields: Student Metrics This section only applies to graduating...order to investigate this we use a modified Lewenstein quantum model in which the cluster is represented by a 1D Coulomb potential for the parent ion

  2. Single-cycle Optical Pulses and Isolated Attosecond Pulse Generation

    Science.gov (United States)

    2012-02-29

    picosecond green light from a frequency-doubled hybrid cryogenic Yb:YAG laser system,” 36 UFO /HFSW 2009 (Arcachon, France, Aug. 31-Sept. 4, 2009...High Fields Short Wavelength,” ( UFO VII – HFSW XIII), Arcachon, France, August 31 – September 4, 2009 (invited). 25) Kyung-Han Hong, Juliet Gopinath

  3. Generation of high harmonics and attosecond pulses with ultrashort ...

    Indian Academy of Sciences (India)

    input Gaussian pulse into a non-diffractive and non-dispersive conical wavepacket [4,5], source of secondary radiation [6], and remote actions to mention a few. ... gas before propagation of the ionizing pulse: NAr(t → −∞) = N0. e and me ...

  4. Attosecond-recollision-controlled selective fragmentation of polyatomic molecules.

    Science.gov (United States)

    Xie, Xinhua; Doblhoff-Dier, Katharina; Roither, Stefan; Schöffler, Markus S; Kartashov, Daniil; Xu, Huailiang; Rathje, Tim; Paulus, Gerhard G; Baltuška, Andrius; Gräfe, Stefanie; Kitzler, Markus

    2012-12-14

    Control over various fragmentation reactions of a series of polyatomic molecules (acetylene, ethylene, 1,3-butadiene) by the optical waveform of intense few-cycle laser pulses is demonstrated experimentally. We show both experimentally and theoretically that the responsible mechanism is inelastic ionization from inner-valence molecular orbitals by recolliding electron wave packets, whose recollision energy in few-cycle ionizing laser pulses strongly depends on the optical waveform. Our work demonstrates an efficient and selective way of predetermining fragmentation and isomerization reactions in polyatomic molecules on subfemtosecond time scales.

  5. Relativistic stellar dynamics

    International Nuclear Information System (INIS)

    Contopoulos, G.

    1983-01-01

    In this paper, three main areas of relativistic stellar dynamics are reviewed: (a) The dynamics of clusters, or nuclei of galaxies, of very high density; (b) The dynamics of systems containing a massive black hole; and (c) The dynamics of particles (and photons) in an expanding Universe. The emphasis is on the use of orbit perturbations. (Auth.)

  6. Principles of magnetoplasma dynamics

    International Nuclear Information System (INIS)

    Woods, L.C.

    1987-01-01

    A self-contained account is given of magnetoplasma dynamics covering fluid dynamics, thermodynamics, kinetic theory of gases, particle dynamics and electromagnetism. The six chapter headings are, basic concepts, magnetohydrodynamics, dynamics of charged particles, transport in a magnetoplasma, magnetoplasma shock waves, and transport in tokamaks. There are 231 references. (U.K.)

  7. Fundamentals of structural dynamics

    CERN Document Server

    Craig, Roy R

    2006-01-01

    From theory and fundamentals to the latest advances in computational and experimental modal analysis, this is the definitive, updated reference on structural dynamics.This edition updates Professor Craig's classic introduction to structural dynamics, which has been an invaluable resource for practicing engineers and a textbook for undergraduate and graduate courses in vibrations and/or structural dynamics. Along with comprehensive coverage of structural dynamics fundamentals, finite-element-based computational methods, and dynamic testing methods, this Second Edition includes new and e

  8. Charge carrier dynamics of methylammonium lead iodide: from PbI₂-rich to low-dimensional broadly emitting perovskites.

    Science.gov (United States)

    Klein, Johannes R; Flender, Oliver; Scholz, Mirko; Oum, Kawon; Lenzer, Thomas

    2016-04-28

    We provide an investigation of the charge carrier dynamics of the (MAI)(x)(PbI2)(1-x) system in the range x = 0.32-0.90 following the recently published "pseudobinary phase-composition processing diagram" of Song et al. (Chem. Mater., 2015, 27, 4612). The dynamics were studied using ultrafast pump-supercontinuum probe spectroscopy over the pump fluence range 2-50 μJ cm(-2), allowing for a wide variation of the initial carrier density. At high MAI excess (x = 0.90), low-dimensional perovskites (LDPs) are formed, and their luminescence spectra are significantly blue-shifted by ca. 50 nm and broadened compared to the 3D perovskite. The shift is due to quantum confinement effects, and the inhomogeneous broadening arises from different low-dimensional structures (predominantly 2D, but presumably also 1D and 0D). Accurate transient carrier temperatures are extracted from the transient absorption spectra. The regimes of carrier-carrier, carrier-optical phonon and acoustic phonon scattering are clearly distinguished. Perovskites with mole fractions x ≤ 0.71 exhibit extremely fast carrier cooling (ca. 300 fs) at low fluence of 2 μJ cm(-2), however cooling slows down significantly at high fluence of 50 μJ cm(-2) due to the "hot phonon effect" (ca. 2.8 ps). A kinetic analysis of the electron-hole recombination dynamics provides second-order recombination rate constants k2 which decrease from 5.3 to 1.5 × 10(-9) cm(3) s(-1) in the range x = 0.32-0.71. In contrast, recombination in the LDPs (x = 0.90) is more than one order of magnitude faster, 6.4 × 10(-8) cm(3) s(-1), which is related to the confined perovskite structure. Recombination in these LDPs should be however still slow enough for their potential application as efficient broadband emitters or solar light-harvesting materials.

  9. Generation and characterization of atto second pulses

    International Nuclear Information System (INIS)

    Mairesse, Y.

    2005-07-01

    Atto-second pulse trains in the extreme ultraviolet range can be produced by high-order harmonic generation, by focusing an intense femtosecond pulse in a rare gas jet. In this thesis, we present a temporal characterization of this radiation on the femtosecond and atto-second timescales. By transposing a spectral interferometry technique commonly used in the infrared range (SPIDER), we make a complete single-shot characterization of the temporal profile of individual harmonics, on the femtosecond timescale. In a second part, we study experimentally the atto-second structure of the harmonic radiation, and demonstrate a temporal drift in the emission: the lowest harmonics are emitted before the highest ones. This chirp, which is directly related to the electron dynamics in the generation process, imposes a lower limit to the duration that can be achieved by increasing the spectral range. We show how generating conditions can be optimized in order to enhance the synchronization in the emission, and how atto-second pulses can be re-compressed. Last, we propose a new technique for the complete characterization of arbitrary atto-second pulses: FROGCRAB. This method would allow simultaneous measurements of the femtosecond and atto-second structures of the radiation, and thus a complete knowledge of the atto-second light source in the perspective of applications. (author)

  10. Dynamic light scattering. Observation of polymer dynamics

    International Nuclear Information System (INIS)

    Hiroi, Takashi

    2015-01-01

    Dynamic light scattering is a technique to measure properties of polymer solutions such as size distribution. Principle of dynamic light scattering is briefly explained. Sometime dynamic light scattering is regarded as the observation of Doppler shift of scattered light. First, the difficulty for the direct observation of this Doppler shift is mentioned. Then the measurement by using a time correlation function is introduced. Measuring techniques for dynamic light scattering are also introduced. In addition to homodyne and heterodyne detection techniques, the technique called partial heterodyne method is also introduced. This technique is useful for the analysis of nonergodic medium such as polymer gels. Then the application of this technique to condensed suspension is briefly reviewed. As one of the examples, a dynamic light scattering microscope is introduced. By using this apparatus, we can measure the concentration dependence of the size distribution of polymer solutions. (author)

  11. Dynamic statistical information theory

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In recent years we extended Shannon static statistical information theory to dynamic processes and established a Shannon dynamic statistical information theory, whose core is the evolution law of dynamic entropy and dynamic information. We also proposed a corresponding Boltzmman dynamic statistical information theory. Based on the fact that the state variable evolution equation of respective dynamic systems, i.e. Fokker-Planck equation and Liouville diffusion equation can be regarded as their information symbol evolution equation, we derived the nonlinear evolution equations of Shannon dynamic entropy density and dynamic information density and the nonlinear evolution equations of Boltzmann dynamic entropy density and dynamic information density, that describe respectively the evolution law of dynamic entropy and dynamic information. The evolution equations of these two kinds of dynamic entropies and dynamic informations show in unison that the time rate of change of dynamic entropy densities is caused by their drift, diffusion and production in state variable space inside the systems and coordinate space in the transmission processes; and that the time rate of change of dynamic information densities originates from their drift, diffusion and dissipation in state variable space inside the systems and coordinate space in the transmission processes. Entropy and information have been combined with the state and its law of motion of the systems. Furthermore we presented the formulas of two kinds of entropy production rates and information dissipation rates, the expressions of two kinds of drift information flows and diffusion information flows. We proved that two kinds of information dissipation rates (or the decrease rates of the total information) were equal to their corresponding entropy production rates (or the increase rates of the total entropy) in the same dynamic system. We obtained the formulas of two kinds of dynamic mutual informations and dynamic channel

  12. Structure, Reactivity and Dynamics

    Indian Academy of Sciences (India)

    Understanding structure, reactivity and dynamics is the core issue in chemical ... functional theory (DFT) calculations, molecular dynamics (MD) simulations, light- ... between water and protein oxygen atoms, the superionic conductors which ...

  13. Modeling dynamic swarms

    KAUST Repository

    Ghanem, Bernard; Ahuja, Narendra

    2013-01-01

    This paper proposes the problem of modeling video sequences of dynamic swarms (DSs). We define a DS as a large layout of stochastically repetitive spatial configurations of dynamic objects (swarm elements) whose motions exhibit local spatiotemporal

  14. Spaces of Dynamical Systems

    CERN Document Server

    Pilyugin, Sergei Yu

    2012-01-01

    Dynamical systems are abundant in theoretical physics and engineering. Their understanding, with sufficient mathematical rigor, is vital to solving many problems. This work conveys the modern theory of dynamical systems in a didactically developed fashion.In addition to topological dynamics, structural stability and chaotic dynamics, also generic properties and pseudotrajectories are covered, as well as nonlinearity. The author is an experienced book writer and his work is based on years of teaching.

  15. State-to-state dynamics at the gas-liquid metal interface: rotationally and electronically inelastic scattering of NO[2Π(1/2)(0.5)] from molten gallium.

    Science.gov (United States)

    Ziemkiewicz, Michael P; Roscioli, Joseph R; Nesbitt, David J

    2011-06-21

    Jet cooled NO molecules are scattered at 45° with respect to the surface normal from a liquid gallium surface at E(inc) from 1.0(3) to 20(6) kcal/mol to probe rotationally and electronically inelastic scattering from a gas-molten metal interface (numbers in parenthesis represent 1σ uncertainty in the corresponding final digits). Scattered populations are detected at 45° by confocal laser induced fluorescence (LIF) on the γ(0-0) and γ(1-1) A(2)Σ ← X(2)Π(Ω) bands, yielding rotational, spin-orbit, and λ-doublet population distributions. Scattering of low speed NO molecules results in Boltzmann distributions with effective temperatures considerably lower than that of the surface, in respectable agreement with the Bowman-Gossage rotational cooling model [J. M. Bowman and J. L. Gossage, Chem. Phys. Lett. 96, 481 (1983)] for desorption from a restricted surface rotor state. Increasing collision energy results in a stronger increase in scattered NO rotational energy than spin-orbit excitation, with an opposite trend noted for changes in surface temperature. The difference between electronic and rotational dynamics is discussed in terms of the possible influence of electron hole pair excitations in the conducting metal. While such electronically non-adiabatic processes can also influence vibrational dynamics, the γ(1-1) band indicates rotational energy transfer is compared from a hard cube model perspective with previous studies of NO scattering from single crystal solid surfaces. Despite a lighter atomic mass (70 amu), the liquid Ga surface is found to promote translational to rotational excitation more efficiently than Ag(111) (108 amu) and nearly as effectively as Au(111) (197 amu). The enhanced propensity for Ga(l) to transform incident translational energy into rotation is discussed in terms of temperature-dependent capillary wave excitation of the gas-liquid metal interface. © 2011 American Institute of Physics

  16. Dynamics of Media Attention

    NARCIS (Netherlands)

    Traag, V.A.; Reinanda, R.; Hicks, J.; van Klinken, G.; Aziz-Alaoui, M.A.; Bertelle, C.; Liu, X.; Olivier, D.

    2014-01-01

    Studies of human attention dynamics analyses how attention is focused on specific topics, issues or people. In online social media, there are clear signs of exogenous shocks, bursty dynamics, and an exponential or powerlaw lifetime distribution. We here analyse the attention dynamics of traditional

  17. Intramolecular and nonlinear dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Davis, M.J. [Argonne National Laboratory, IL (United States)

    1993-12-01

    Research in this program focuses on three interconnected areas. The first involves the study of intramolecular dynamics, particularly of highly excited systems. The second area involves the use of nonlinear dynamics as a tool for the study of molecular dynamics and complex kinetics. The third area is the study of the classical/quantum correspondence for highly excited systems, particularly systems exhibiting classical chaos.

  18. PREFACE: Dynamics of wetting Dynamics of wetting

    Science.gov (United States)

    Grest, Gary S.; Oshanin, Gleb; Webb, Edmund B., III

    2009-11-01

    Capillary phenomena associated with fluids wetting other condensed matter phases have drawn great scientific interest for hundreds of years; consider the recent bicentennial celebration of Thomas Young's paper on equilibrium contact angles, describing the geometric shape assumed near a three phase contact line in terms of the relevant surface energies of the constituent phases [1]. Indeed, nearly a century has passed since the seminal papers of Lucas and Washburn, describing dynamics of capillary imbibition [2, 3]. While it is generally appreciated that dynamics of fluid wetting processes are determined by the degree to which a system is out of capillary equilibrium, myriad complications exist that challenge the fundamental understanding of dynamic capillary phenomena. The topic has gathered much interest from recent Nobel laureate Pierre-Gilles de Gennes, who provided a seminal review of relevant dissipation mechanisms for fluid droplets spreading on solid surfaces [4] Although much about the dynamics of wetting has been revealed, much remains to be learned and intrinsic technological and fundamental interest in the topic drives continuing high levels of research activity. This is enabled partly by improved experimental capabilities for resolving wetting processes at increasingly finer temporal, spatial, and chemical resolution. Additionally, dynamic wetting research advances via higher fidelity computational modeling capabilities, which drive more highly refined theory development. The significance of this topic both fundamentally and technologically has resulted in a number of reviews of research activity in wetting dynamics. One recent example addresses the evaluation of existing wetting dynamics theories from an experimentalist's perspective [5]. A Current Opinion issue was recently dedicated to high temperature capillarity, including dynamics of high temperature spreading [6]. New educational tools have recently emerged for providing instruction in wetting

  19. Dynamic link: user's manual

    International Nuclear Information System (INIS)

    Harada, Hiroo; Asai, Kiyoshi; Kihara, Kazuhisa.

    1981-09-01

    The purpose of dynamic link facility is to link a load module dynamically only when it is used in execution time. The facility is very useful for development, execution and maintenance of a large scale computer program which is too big to be saved as one load module in main memory, or it is poor economy to save it due to many unused subroutines depending on an input. It is also useful for standardization and common utilization of programs. Standard usage of dynamic link facility of FACOM M-200 computer system, a software tool which analyzes the effect of dynamic link facility and application of dynamic link to nuclear codes are described. (author)

  20. Collaborative research: Dynamics of electrostatic solitary waves and their effects on current layers

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Li-Jen

    2014-04-18

    The project has accomplished the following achievements including the goals outlined in the original proposal. Generation and measurements of Debye-scale electron holes in laboratory: We have generated by beam injections electron solitary waves in the LAPD experiments. The measurements were made possible by the fabrication of the state-of-the-art microprobes at UCLA to measure Debye-scale electric fields [Chiang et al., 2011]. We obtained a result that challenged the state of knowledge about electron hole generation. We found that the electron holes were not due to two-stream instability, but generated by a current-driven instability that also generated whistler-mode waves [Lefebvre et al., 2011, 2010b]. Most of the grant supported a young research scientist Bertrand Lefebvre who led the dissemination of the laboratory experimental results. In addition to two publications, our work relevant to the laboratory experiments on electron holes has resulted in 7 invited talks [Chen, 2007, 2009; Pickett et al., 2009a; Lefebvre et al., 2010a; Pickett et al., 2010; Chen et al., 2011c, b] (including those given by the co-I Jolene Pickett) and 2 contributed talks [Lefebvre et al., 2009b, a]. Discovery of elecctron phase-space-hole structure in the reconnection electron layer: Our theoretical analyses and simulations under this project led to the discovery of an inversion electric field layer whose phase-space signature is an electron hole within the electron diffusion layer in 2D anti-parallel reconnection [Chen et al., 2011a]. We carried out particle tracing studies to understand the electron orbits that result in the phase-space hole structure. Most importantly, we showed that the current density in the electron layer is limited in collisionless reconnection with negligible guide field by the cyclotron turning of meandering electrons. Comparison of electrostatic solitary waves in current layers observed by Cluster and in LAPD: We compared the ESWs observed in a supersubstorm

  1. Complexity and Dynamical Depth

    Directory of Open Access Journals (Sweden)

    Terrence Deacon

    2014-07-01

    Full Text Available We argue that a critical difference distinguishing machines from organisms and computers from brains is not complexity in a structural sense, but a difference in dynamical organization that is not well accounted for by current complexity measures. We propose a measure of the complexity of a system that is largely orthogonal to computational, information theoretic, or thermodynamic conceptions of structural complexity. What we call a system’s dynamical depth is a separate dimension of system complexity that measures the degree to which it exhibits discrete levels of nonlinear dynamical organization in which successive levels are distinguished by local entropy reduction and constraint generation. A system with greater dynamical depth than another consists of a greater number of such nested dynamical levels. Thus, a mechanical or linear thermodynamic system has less dynamical depth than an inorganic self-organized system, which has less dynamical depth than a living system. Including an assessment of dynamical depth can provide a more precise and systematic account of the fundamental difference between inorganic systems (low dynamical depth and living systems (high dynamical depth, irrespective of the number of their parts and the causal relations between them.

  2. Dynamic and quasi-dynamic multileaf collimation

    International Nuclear Information System (INIS)

    Bortfeld, T.

    1995-01-01

    Several recent investigations deal with the problem of how to produce arbitrary two-dimensional x-ray fluence distributions by means of a multileaf collimator (MLC), an approach, which could be called multileaf modulation. The goal of this approach is to facilitate the delivery of compensated or intensity-modulated fields. The present work gives an overview of these developments. The hardware requirements on MLCs for this special application are specified. Most commercially available MLCs fulfill these requirement sufficiently, however, the MLC control software is generally not capable of controlling an MLC dynamically. There is also the question of how to verify the dynamic movement of the leaves. Some minimum requirements on a control software suitable for application in clinical practice are therefore specified. An alternative, the stepwise or 'quasi-dynamic' movement of the MLC-leaves, is also discussed with respect to practicality. In this case the control is easier, but the demands on the stability of the accelerator for small dose deliveries are higher. Nevertheless, it can be expected that, for reasons of ease of control and verification, the quasi-dynamic technique will become the method of choice in the near future, while the slightly more effective fully dynamic technique will become available later in the future. In any case, multileaf modulation is an interesting and important alternative to the tomotherapy-concept

  3. Synchronization dynamics of two different dynamical systems

    International Nuclear Information System (INIS)

    Luo, Albert C.J.; Min Fuhong

    2011-01-01

    Highlights: → Synchronization dynamics of two distinct dynamical systems. → Synchronization, de-synchronization and instantaneous synchronization. → A controlled pendulum synchronizing with the Duffing oscillator. → Synchronization invariant set. → Synchronization parameter map. - Abstract: In this paper, synchronization dynamics of two different dynamical systems is investigated through the theory of discontinuous dynamical systems. The necessary and sufficient conditions for the synchronization, de-synchronization and instantaneous synchronization (penetration or grazing) are presented. Using such a synchronization theory, the synchronization of a controlled pendulum with the Duffing oscillator is systematically discussed as a sampled problem, and the corresponding analytical conditions for the synchronization are presented. The synchronization parameter study is carried out for a better understanding of synchronization characteristics of the controlled pendulum and the Duffing oscillator. Finally, the partial and full synchronizations of the controlled pendulum with periodic and chaotic motions are presented to illustrate the analytical conditions. The synchronization of the Duffing oscillator and pendulum are investigated in order to show the usefulness and efficiency of the methodology in this paper. The synchronization invariant domain is obtained. The technique presented in this paper should have a wide spectrum of applications in engineering. For example, this technique can be applied to the maneuvering target tracking, and the others.

  4. Dynamic Boiler Performance

    DEFF Research Database (Denmark)

    Sørensen, Kim

    Traditionally, boilers have been designed mainly focussing on the static operation of the plant. The dynamic capability has been given lower priority and the analysis has typically been limited to assuring that the plant was not over-stressed due to large temperature gradients. New possibilities...... developed. Analyzing boilers for dynamic operation gives rise to a number of opposing aims: shrinking and swelling, steam quality, stress levels, control system/philosophy, pressurization etc. Common for these opposing aims is that an optimum can be found for selected operation conditions. The framework has...... for buying and selling energy has increased the focus on the dynamic operation capability, efciency, emissions etc. For optimizing the design of boilers for dynamic operation a quantication of the dynamic capability is needed. A framework for optimizing design of boilers for dynamic operation has been...

  5. Nonlinear dynamics and astrophysics

    International Nuclear Information System (INIS)

    Vallejo, J. C.; Sanjuan, M. A. F.

    2000-01-01

    Concepts and techniques from Nonlinear Dynamics, also known as Chaos Theory, have been applied successfully to several astrophysical fields such as orbital motion, time series analysis or galactic dynamics, providing answers to old questions but also opening a few new ones. Some of these topics are described in this review article, showing the basis of Nonlinear Dynamics, and how it is applied in Astrophysics. (Author)

  6. Record Statistics and Dynamics

    DEFF Research Database (Denmark)

    Sibani, Paolo; Jensen, Henrik J.

    2009-01-01

    with independent random increments. The term record dynamics covers the rather new idea that records may, in special situations, have measurable dynamical consequences. The approach applies to the aging dynamics of glasses and other systems with multiple metastable states. The basic idea is that record sizes...... fluctuations of e. g. the energy are able to push the system past some sort of ‘edge of stability’, inducing irreversible configurational changes, whose statistics then closely follows the statistics of record fluctuations....

  7. Dynamics of unstable systems

    International Nuclear Information System (INIS)

    Posch, H.A.; Narnhofer, H.; Thirring, W.

    1990-01-01

    We study the dynamics of classical particles interacting with attractive Gaussian potentials. This system is thermodynamically not stable and exhibits negative specific heat. The results of the computer simulation of the dynamics are discussed in comparison with various theories. In particular, we find that the condensed phase is a stationary solution of the Vlasov equation, but the Vlasov dynamics cannot describe the collapse. 14 refs., 1 tab., 11 figs. (Authors)

  8. Dynamical principles in neuroscience

    International Nuclear Information System (INIS)

    Rabinovich, Mikhail I.; Varona, Pablo; Selverston, Allen I.; Abarbanel, Henry D. I.

    2006-01-01

    Dynamical modeling of neural systems and brain functions has a history of success over the last half century. This includes, for example, the explanation and prediction of some features of neural rhythmic behaviors. Many interesting dynamical models of learning and memory based on physiological experiments have been suggested over the last two decades. Dynamical models even of consciousness now exist. Usually these models and results are based on traditional approaches and paradigms of nonlinear dynamics including dynamical chaos. Neural systems are, however, an unusual subject for nonlinear dynamics for several reasons: (i) Even the simplest neural network, with only a few neurons and synaptic connections, has an enormous number of variables and control parameters. These make neural systems adaptive and flexible, and are critical to their biological function. (ii) In contrast to traditional physical systems described by well-known basic principles, first principles governing the dynamics of neural systems are unknown. (iii) Many different neural systems exhibit similar dynamics despite having different architectures and different levels of complexity. (iv) The network architecture and connection strengths are usually not known in detail and therefore the dynamical analysis must, in some sense, be probabilistic. (v) Since nervous systems are able to organize behavior based on sensory inputs, the dynamical modeling of these systems has to explain the transformation of temporal information into combinatorial or combinatorial-temporal codes, and vice versa, for memory and recognition. In this review these problems are discussed in the context of addressing the stimulating questions: What can neuroscience learn from nonlinear dynamics, and what can nonlinear dynamics learn from neuroscience?

  9. Dynamical principles in neuroscience

    Science.gov (United States)

    Rabinovich, Mikhail I.; Varona, Pablo; Selverston, Allen I.; Abarbanel, Henry D. I.

    2006-10-01

    Dynamical modeling of neural systems and brain functions has a history of success over the last half century. This includes, for example, the explanation and prediction of some features of neural rhythmic behaviors. Many interesting dynamical models of learning and memory based on physiological experiments have been suggested over the last two decades. Dynamical models even of consciousness now exist. Usually these models and results are based on traditional approaches and paradigms of nonlinear dynamics including dynamical chaos. Neural systems are, however, an unusual subject for nonlinear dynamics for several reasons: (i) Even the simplest neural network, with only a few neurons and synaptic connections, has an enormous number of variables and control parameters. These make neural systems adaptive and flexible, and are critical to their biological function. (ii) In contrast to traditional physical systems described by well-known basic principles, first principles governing the dynamics of neural systems are unknown. (iii) Many different neural systems exhibit similar dynamics despite having different architectures and different levels of complexity. (iv) The network architecture and connection strengths are usually not known in detail and therefore the dynamical analysis must, in some sense, be probabilistic. (v) Since nervous systems are able to organize behavior based on sensory inputs, the dynamical modeling of these systems has to explain the transformation of temporal information into combinatorial or combinatorial-temporal codes, and vice versa, for memory and recognition. In this review these problems are discussed in the context of addressing the stimulating questions: What can neuroscience learn from nonlinear dynamics, and what can nonlinear dynamics learn from neuroscience?

  10. Computational Fluid Dynamics

    International Nuclear Information System (INIS)

    Myeong, Hyeon Guk

    1999-06-01

    This book deals with computational fluid dynamics with basic and history of numerical fluid dynamics, introduction of finite volume method using one-dimensional heat conduction equation, solution of two-dimensional heat conduction equation, solution of Navier-Stokes equation, fluid with heat transport, turbulent flow and turbulent model, Navier-Stokes solution by generalized coordinate system such as coordinate conversion, conversion of basic equation, program and example of calculation, application of abnormal problem and high speed solution of numerical fluid dynamics.

  11. Double dynamic scaling in human communication dynamics

    Science.gov (United States)

    Wang, Shengfeng; Feng, Xin; Wu, Ye; Xiao, Jinhua

    2017-05-01

    In the last decades, human behavior has been deeply understanding owing to the huge quantities data of human behavior available for study. The main finding in human dynamics shows that temporal processes consist of high-activity bursty intervals alternating with long low-activity periods. A model, assuming the initiator of bursty follow a Poisson process, is widely used in the modeling of human behavior. Here, we provide further evidence for the hypothesis that different bursty intervals are independent. Furthermore, we introduce a special threshold to quantitatively distinguish the time scales of complex dynamics based on the hypothesis. Our results suggest that human communication behavior is a composite process of double dynamics with midrange memory length. The method for calculating memory length would enhance the performance of many sequence-dependent systems, such as server operation and topic identification.

  12. Introduction to dynamic programming

    CERN Document Server

    Cooper, Leon; Rodin, E Y

    1981-01-01

    Introduction to Dynamic Programming provides information pertinent to the fundamental aspects of dynamic programming. This book considers problems that can be quantitatively formulated and deals with mathematical models of situations or phenomena that exists in the real world.Organized into 10 chapters, this book begins with an overview of the fundamental components of any mathematical optimization model. This text then presents the details of the application of dynamic programming to variational problems. Other chapters consider the application of dynamic programming to inventory theory, Mark

  13. Essential dynamics and relativity

    CERN Document Server

    O'Donnell, Peter J

    2014-01-01

    Essential Dynamics & Relativity provides students with an introduction to the core aspects of dynamics and special relativity. The author reiterates important ideas and terms throughout and covers concepts that are often missing from other textbooks at this level. He also places each topic within the wider constructs of the theory, without jumping from topic to topic to illustrate a point.The first section of the book focuses on dynamics, discussing the basic aspects of single particle motion and analyzing the motion of multi-particle systems. The book also explains the dynamical behavior of b

  14. Dynamical Systems Conference

    CERN Document Server

    Gils, S; Hoveijn, I; Takens, F; Nonlinear Dynamical Systems and Chaos

    1996-01-01

    Symmetries in dynamical systems, "KAM theory and other perturbation theories", "Infinite dimensional systems", "Time series analysis" and "Numerical continuation and bifurcation analysis" were the main topics of the December 1995 Dynamical Systems Conference held in Groningen in honour of Johann Bernoulli. They now form the core of this work which seeks to present the state of the art in various branches of the theory of dynamical systems. A number of articles have a survey character whereas others deal with recent results in current research. It contains interesting material for all members of the dynamical systems community, ranging from geometric and analytic aspects from a mathematical point of view to applications in various sciences.

  15. Engineering quantum dynamics

    International Nuclear Information System (INIS)

    Lloyd, Seth; Viola, Lorenza

    2002-01-01

    The ability to perform measurements on a quantum system, combined with the ability to feed back the measurement results via coherent control, allows one to control the system to follow any desired coherent or incoherent quantum dynamics. Such universal dynamical control can be achieved, in principle, through the repeated application of only two coherent control operations and a simple 'Yes-No' measurement. As a consequence, a quantum computer can simulate an arbitrary open-system dynamics using just one qubit more than required to simulate closed-system dynamics

  16. Modern fluid dynamics

    CERN Document Server

    Kleinstreuer, Clement

    2018-01-01

    Modern Fluid Dynamics, Second Edition provides up-to-date coverage of intermediate and advanced fluids topics. The text emphasizes fundamentals and applications, supported by worked examples and case studies. Scale analysis, non-Newtonian fluid flow, surface coating, convection heat transfer, lubrication, fluid-particle dynamics, microfluidics, entropy generation, and fluid-structure interactions are among the topics covered. Part A presents fluids principles, and prepares readers for the applications of fluid dynamics covered in Part B, which includes computer simulations and project writing. A review of the engineering math needed for fluid dynamics is included in an appendix.

  17. Control of dynamical localization

    International Nuclear Information System (INIS)

    Gong Jiangbin; Woerner, Hans Jakob; Brumer, Paul

    2003-01-01

    Control over the quantum dynamics of chaotic kicked rotor systems is demonstrated. Specifically, control over a number of quantum coherent phenomena is achieved by a simple modification of the kicking field. These include the enhancement of the dynamical localization length, the introduction of classical anomalous diffusion assisted control for systems far from the semiclassical regime, and the observation of a variety of strongly nonexponential line shapes for dynamical localization. The results provide excellent examples of controlled quantum dynamics in a system that is classically chaotic and offer opportunities to explore quantum fluctuations and correlations in quantum chaos

  18. Nonlinear dynamics and complexity

    CERN Document Server

    Luo, Albert; Fu, Xilin

    2014-01-01

    This important collection presents recent advances in nonlinear dynamics including analytical solutions, chaos in Hamiltonian systems, time-delay, uncertainty, and bio-network dynamics. Nonlinear Dynamics and Complexity equips readers to appreciate this increasingly main-stream approach to understanding complex phenomena in nonlinear systems as they are examined in a broad array of disciplines. The book facilitates a better understanding of the mechanisms and phenomena in nonlinear dynamics and develops the corresponding mathematical theory to apply nonlinear design to practical engineering.

  19. Structural Dynamics Laboratory (SDL)

    Data.gov (United States)

    Federal Laboratory Consortium — Structural dynamic testing is performed to verify the survivability of a component or assembly when exposed to vibration stress screening, or a controlled simulation...

  20. Silicon as a virtual plasmonic material: Acquisition of its transient optical constants and the ultrafast surface plasmon-polariton excitation

    Energy Technology Data Exchange (ETDEWEB)

    Danilov, P. A.; Ionin, A. A.; Kudryashov, S. I., E-mail: sikudr@sci.lebedev.ru; Makarov, S. V.; Rudenko, A. A. [Lebedev Physical Institute (Russian Federation); Saltuganov, P. N. [Moscow Institute of Physics and Technology (State University) (Russian Federation); Seleznev, L. V.; Yurovskikh, V. I.; Zayarny, D. A. [Lebedev Physical Institute (Russian Federation); Apostolova, T. [Bulgarian Academy of Sciences, Institute for Nuclear Research and Nuclear Energetics (Bulgaria)

    2015-06-15

    Ultrafast intense photoexcitation of a silicon surface is complementarily studied experimentally and theoretically, with its prompt optical dielectric function obtained by means of time-resolved optical reflection microscopy and the underlying electron-hole plasma dynamics modeled numerically, using a quantum kinetic approach. The corresponding transient surface plasmon-polariton (SPP) dispersion curves of the photo-excited material were simulated as a function of the electron-hole plasma density, using the derived optical dielectric function model, and directly mapped at several laser photon energies, measuring spatial periods of the corresponding SPP-mediated surface relief nanogratings. The unusual spectral dynamics of the surface plasmon resonance, initially increasing with the increase in the electron-hole plasma density but damped at high interband absorption losses induced by the high-density electron-hole plasma through instantaneous bandgap renormalization, was envisioned through the multi-color mapping.

  1. Vegetation dynamics and dynamic vegetation science

    NARCIS (Netherlands)

    Van der Maarel, E

    1996-01-01

    his contribution presents a review of the development of the study of vegetation dynamics since 1979, in the framework of a jubilee meeting on progress in the study of vegetation. However, an exhaustive review is both impossible and unnecessary. It is impossible within the few pages available

  2. Dynamic defense workshop :

    Energy Technology Data Exchange (ETDEWEB)

    Crosby, Sean Michael; Doak, Justin E.; Haas, Jason Juedes.; Helinski, Ryan; Lamb, Christopher C.

    2013-02-01

    On September 5th and 6th, 2012, the Dynamic Defense Workshop: From Research to Practice brought together researchers from academia, industry, and Sandia with the goals of increasing collaboration between Sandia National Laboratories and external organizations, de ning and un- derstanding dynamic, or moving target, defense concepts and directions, and gaining a greater understanding of the state of the art for dynamic defense. Through the workshop, we broadened and re ned our de nition and understanding, identi ed new approaches to inherent challenges, and de ned principles of dynamic defense. Half of the workshop was devoted to presentations of current state-of-the-art work. Presentation topics included areas such as the failure of current defenses, threats, techniques, goals of dynamic defense, theory, foundations of dynamic defense, future directions and open research questions related to dynamic defense. The remainder of the workshop was discussion, which was broken down into sessions on de ning challenges, applications to host or mobile environments, applications to enterprise network environments, exploring research and operational taxonomies, and determining how to apply scienti c rigor to and investigating the eld of dynamic defense.

  3. Structural Dynamics, Vol. 9

    DEFF Research Database (Denmark)

    Nielsen, Søren R.K.

    This book has been prepared for the course on Computational Dynamics given at the 8th semester at the structural program in civil engineering at Aalborg University.......This book has been prepared for the course on Computational Dynamics given at the 8th semester at the structural program in civil engineering at Aalborg University....

  4. Nonlinear dynamics in Nuclotron

    International Nuclear Information System (INIS)

    Dinev, D.

    1997-01-01

    The paper represents an extensive study of the nonlinear beam dynamics in the Nuclotron. Chromatic effects, including the dependence of the betatron tunes on the amplitude, and chromatic perturbations have been investigated taking into account the measured field imperfections. Beam distortion, smear, dynamic aperture and nonlinear acceptance have been calculated for different particle energies and betatron tunes

  5. Dynamic Shannon Coding

    OpenAIRE

    Gagie, Travis

    2005-01-01

    We present a new algorithm for dynamic prefix-free coding, based on Shannon coding. We give a simple analysis and prove a better upper bound on the length of the encoding produced than the corresponding bound for dynamic Huffman coding. We show how our algorithm can be modified for efficient length-restricted coding, alphabetic coding and coding with unequal letter costs.

  6. Dynamic paradigm of turbulence

    International Nuclear Information System (INIS)

    Mukhamedov, Alfred M.

    2006-01-01

    In this paper a dynamic paradigm of turbulence is proposed. The basic idea consists in the novel definition of chaotic structure given with the help of Pfaff system of PDE associated with the turbulent dynamics. A methodological analysis of the new and the former paradigm is produced

  7. Dynamic Capabilities and Performance

    DEFF Research Database (Denmark)

    Wilden, Ralf; Gudergan, Siegfried P.; Nielsen, Bo Bernhard

    2013-01-01

    are contingent on the competitive intensity faced by firms. Our findings demonstrate the performance effects of internal alignment between organizational structure and dynamic capabilities, as well as the external fit of dynamic capabilities with competitive intensity. We outline the advantages of PLS...

  8. Dynamic Gaming Platform (DGP)

    Science.gov (United States)

    2009-04-01

    GAMING PLATFORM (DGP) Lockheed Martin Corporation...YYYY) APR 09 2. REPORT TYPE Final 3. DATES COVERED (From - To) Jul 07 – Mar 09 4. TITLE AND SUBTITLE DYNAMIC GAMING PLATFORM (DGP) 5a...CMU Carnegie Mellon University DGP Dynamic Gaming Platform GA Genetic Algorithm IARPA Intelligence Advanced Research Projects Activity LM ATL Lockheed Martin Advanced Technology Laboratories PAINT ProActive INTelligence

  9. Dynamic covalent surfactants

    NARCIS (Netherlands)

    Minkenberg, C.B.

    2012-01-01

    In this thesis the development of surfactant aggregates with fast exchange dynamics between the aggregated and non-aggregated state is described. Dynamic surfactant exchange plays an important role in natural systems, for instance in cell signaling, cell division, and uptake and release of cargo.

  10. Dynamics on the Circle

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 8; Issue 11. Dynamics on the Circle - Interval Dynamics and Rotation Number. Siddhartha Gadgil. General Article Volume 8 Issue 11 November 2003 pp 25-36. Fulltext. Click here to view fulltext PDF. Permanent link:

  11. Dynamic Speaking Assessments

    Science.gov (United States)

    Hill, Kent; Sabet, Mehran

    2009-01-01

    This article describes an attempt to adopt dynamic assessment (DA) methods in classroom speaking assessments. The study reported in this article focused on four particular applications of dynamic speaking assessment (DSA). The first, "mediated assistance" (MA), involves interaction between an assistor and a learner to reveal problems in…

  12. Dynamical supersymmetry breaking

    International Nuclear Information System (INIS)

    Affleck, I.

    1985-03-01

    Supersymmetry, and in particular, dynamical supersymmetry breaking, offers the hope of a natural solution of the gauge hierarchy problem in grand unification. I briefly review recent work on dynamical supersymmetry breaking in four-dimensional Higgs theories and its application to grand unified model building

  13. Dynamic Latent Classification Model

    DEFF Research Database (Denmark)

    Zhong, Shengtong; Martínez, Ana M.; Nielsen, Thomas Dyhre

    as possible. Motivated by this problem setting, we propose a generative model for dynamic classification in continuous domains. At each time point the model can be seen as combining a naive Bayes model with a mixture of factor analyzers (FA). The latent variables of the FA are used to capture the dynamics...

  14. Dynamic combinatorial chemistry

    NARCIS (Netherlands)

    Otto, Sijbren; Furlan, Ricardo L.E.; Sanders, Jeremy K.M.

    2002-01-01

    A combinatorial library that responds to its target by increasing the concentration of strong binders at the expense of weak binders sounds ideal. Dynamic combinatorial chemistry has the potential to achieve exactly this. In this review, we will highlight the unique features that distinguish dynamic

  15. Bursty human dynamics

    CERN Document Server

    Karsai, Márton; Kaski, Kimmo

    2018-01-01

    This book provides a comprehensive overview on emergent bursty patterns in the dynamics of human behaviour. It presents common and alternative understanding of the investigated phenomena, and points out open questions worthy of further investigations. The book is structured as follows. In the introduction the authors discuss the motivation of the field, describe bursty phenomena in case of human behaviour, and relate it to other disciplines. The second chapter addresses the measures commonly used to characterise heterogeneous signals, bursty human dynamics, temporal paths, and correlated behaviour. These definitions are first introduced to set the basis for the discussion of the third chapter about the observations of bursty human patterns in the dynamics of individuals, dyadic interactions, and collective behaviour. The subsequent fourth chapter discusses the models of bursty human dynamics. Various mechanisms have been proposed about the source of the heterogeneities in human dynamics, which leads to the in...

  16. Nonlinear dynamics of structures

    CERN Document Server

    Oller, Sergio

    2014-01-01

    This book lays the foundation of knowledge that will allow a better understanding of nonlinear phenomena that occur in structural dynamics.   This work is intended for graduate engineering students who want to expand their knowledge on the dynamic behavior of structures, specifically in the nonlinear field, by presenting the basis of dynamic balance in non‐linear behavior structures due to the material and kinematics mechanical effects.   Particularly, this publication shows the solution of the equation of dynamic equilibrium for structure with nonlinear time‐independent materials (plasticity, damage and frequencies evolution), as well as those time dependent non‐linear behavior materials (viscoelasticity and viscoplasticity). The convergence conditions for the non‐linear dynamic structure solution  are studied, and the theoretical concepts and its programming algorithms are presented.  

  17. Vehicle Dynamics and Control

    CERN Document Server

    Rajamani, Rajesh

    2012-01-01

    Vehicle Dynamics and Control provides a comprehensive coverage of vehicle control systems and the dynamic models used in the development of these control systems. The control system applications covered in the book include cruise control, adaptive cruise control, ABS, automated lane keeping, automated highway systems, yaw stability control, engine control, passive, active and semi-active suspensions, tire-road friction coefficient estimation, rollover prevention, and hybrid electric vehicle. In developing the dynamic model for each application, an effort is made to both keep the model simple enough for control system design but at the same time rich enough to capture the essential features of the dynamics. A special effort has been made to explain the several different tire models commonly used in literature and to interpret them physically. In the second edition of the book, chapters on roll dynamics, rollover prevention and hybrid electric vehicles have been added, and the chapter on electronic stability co...

  18. Ab initio molecular dynamics calculations on scattering of hyperthermal H atoms from Cu(111) and Au(111)

    Energy Technology Data Exchange (ETDEWEB)

    Kroes, Geert-Jan, E-mail: g.j.kroes@chem.leidenuniv.nl; Pavanello, Michele [Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden (Netherlands); Blanco-Rey, María [Departamento de Física de Materiales, Facultad de Químicas UPV/EHU, Apartado 1072, 20080 Donostia-San Sebastián (Spain); Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián (Spain); Alducin, Maite [Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastián (Spain); Centro de Física de Materiales, Centro Mixto CSIC-UPV/EHU, Paseo Manuel de Lardizabal 5, 20018 Donostia-San Sebastián (Spain); Auerbach, Daniel J. [Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden (Netherlands); Max Planck Institute for Biophysical Chemistry, Göttingen (Germany); Institute for Physical Chemistry, Georg-August University of Göttingen, Göttingen (Germany)

    2014-08-07

    Energy loss from the translational motion of an atom or molecule impinging on a metal surface to the surface may determine whether the incident particle can trap on the surface, and whether it has enough energy left to react with another molecule present at the surface. Although this is relevant to heterogeneous catalysis, the relative extent to which energy loss of hot atoms takes place to phonons or electron-hole pair (ehp) excitation, and its dependence on the system's parameters, remain largely unknown. We address these questions for two systems that present an extreme case of the mass ratio of the incident atom to the surface atom, i.e., H + Cu(111) and H + Au(111), by presenting adiabatic ab initio molecular dynamics (AIMD) predictions of the energy loss and angular distributions for an incidence energy of 5 eV. The results are compared to the results of AIMDEFp calculations modeling energy loss to ehp excitation using an electronic friction (“EF”) model applied to the AIMD trajectories, so that the energy loss to the electrons is calculated “post” (“p”) the computation of the AIMD trajectory. The AIMD calculations predict average energy losses of 0.38 eV for Cu(111) and 0.13-0.14 eV for Au(111) for H-atoms that scatter from these surfaces without penetrating the surface. These energies closely correspond with energy losses predicted with Baule models, which is suggestive of structure scattering. The predicted adiabatic integral energy loss spectra (integrated over all final scattering angles) all display a lowest energy peak at an energy corresponding to approximately 80% of the average adiabatic energy loss for non-penetrative scattering. In the adiabatic limit, this suggests a way of determining the approximate average energy loss of non-penetratively scattered H-atoms from the integral energy loss spectrum of all scattered H-atoms. The AIMDEFp calculations predict that in each case the lowest energy loss peak should show additional energy

  19. Ab initio molecular dynamics calculations on scattering of hyperthermal H atoms from Cu(111) and Au(111).

    Science.gov (United States)

    Kroes, Geert-Jan; Pavanello, Michele; Blanco-Rey, María; Alducin, Maite; Auerbach, Daniel J

    2014-08-07

    Energy loss from the translational motion of an atom or molecule impinging on a metal surface to the surface may determine whether the incident particle can trap on the surface, and whether it has enough energy left to react with another molecule present at the surface. Although this is relevant to heterogeneous catalysis, the relative extent to which energy loss of hot atoms takes place to phonons or electron-hole pair (ehp) excitation, and its dependence on the system's parameters, remain largely unknown. We address these questions for two systems that present an extreme case of the mass ratio of the incident atom to the surface atom, i.e., H + Cu(111) and H + Au(111), by presenting adiabatic ab initio molecular dynamics (AIMD) predictions of the energy loss and angular distributions for an incidence energy of 5 eV. The results are compared to the results of AIMDEFp calculations modeling energy loss to ehp excitation using an electronic friction ("EF") model applied to the AIMD trajectories, so that the energy loss to the electrons is calculated "post" ("p") the computation of the AIMD trajectory. The AIMD calculations predict average energy losses of 0.38 eV for Cu(111) and 0.13-0.14 eV for Au(111) for H-atoms that scatter from these surfaces without penetrating the surface. These energies closely correspond with energy losses predicted with Baule models, which is suggestive of structure scattering. The predicted adiabatic integral energy loss spectra (integrated over all final scattering angles) all display a lowest energy peak at an energy corresponding to approximately 80% of the average adiabatic energy loss for non-penetrative scattering. In the adiabatic limit, this suggests a way of determining the approximate average energy loss of non-penetratively scattered H-atoms from the integral energy loss spectrum of all scattered H-atoms. The AIMDEFp calculations predict that in each case the lowest energy loss peak should show additional energy loss in the

  20. Ionization, photoelectron dynamics and elastic scattering in relativistic, ultra-strong field

    Science.gov (United States)

    Luo, Sui

    Ultrastrong laser-matter interaction has direct bearing to next generation technologies including plasma acceleration, laser fusion and attosecond X-ray generation. The commonly known physics in strong field becomes different as one progress to ultrastrong field. The works presented in this dissertation theoretically study the influence of relativistic effect and magnetic component of the laser field on the ionization, photoelectron dynamics and elastic scattering processes. The influence of magnetic component (B laser) of circularly polarized (CP) ultrastrong fields (up to3 x 1022 W/cm2) on atomic bound state dynamics is investigated. The Poincare plots are used to find the changes in trajectory energies are on the order of a few percent for intensities up to1 x 1022 W/cm2. It is found that at intensities where ionization approaches 50% for the bound state, the small changes from Blaser of the circular polarized light can actually result in a several-fold decrease in ionization probability. The force on the bound electron exerted by the Lorentz force from B laser is perpendicular to the rotating plane of the circular polarized light, and this nature makes those trajectories which are aligned away from the minimum in the potential barrier stabilized against tunneling ionization. Our results provide a classical understanding for ionization in ultrastrong fields and indicate that relativistic effects in ultrastrong field ionization may most easily be seen with CP fields. The photoelectron energy spectra from elastic rescattering in ultrastrong laser fields (up to 2x1019 W/cm2) is studied by using a relativistic adaption of a semi-classical three-step recollision model. The Hartree-Fock scattering potentials are used in calculating the elastic rescattering for both hydrogenlike and noble gas species. It is found that there is a reduction in elastic rescattering for intensities beyond 6 x 1016 W/cm2 when the laser Lorentz deflection of the photoelectron exceeds its

  1. Bayesian dynamic mediation analysis.

    Science.gov (United States)

    Huang, Jing; Yuan, Ying

    2017-12-01

    Most existing methods for mediation analysis assume that mediation is a stationary, time-invariant process, which overlooks the inherently dynamic nature of many human psychological processes and behavioral activities. In this article, we consider mediation as a dynamic process that continuously changes over time. We propose Bayesian multilevel time-varying coefficient models to describe and estimate such dynamic mediation effects. By taking the nonparametric penalized spline approach, the proposed method is flexible and able to accommodate any shape of the relationship between time and mediation effects. Simulation studies show that the proposed method works well and faithfully reflects the true nature of the mediation process. By modeling mediation effect nonparametrically as a continuous function of time, our method provides a valuable tool to help researchers obtain a more complete understanding of the dynamic nature of the mediation process underlying psychological and behavioral phenomena. We also briefly discuss an alternative approach of using dynamic autoregressive mediation model to estimate the dynamic mediation effect. The computer code is provided to implement the proposed Bayesian dynamic mediation analysis. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  2. Dynamics of aesthetic appreciation

    Science.gov (United States)

    Carbon, Claus-Christian

    2012-03-01

    Aesthetic appreciation is a complex cognitive processing with inherent aspects of cold as well as hot cognition. Research from the last decades of empirical has shown that evaluations of aesthetic appreciation are highly reliable. Most frequently, facial attractiveness was used as the corner case for investigating aesthetic appreciation. Evaluating facial attractiveness shows indeed high internal consistencies and impressively high inter-rater reliabilities, even across cultures. Although this indicates general and stable mechanisms underlying aesthetic appreciation, it is also obvious that our taste for specific objects changes dynamically. Aesthetic appreciation on artificial object categories, such as fashion, design or art is inherently very dynamic. Gaining insights into the cognitive mechanisms that trigger and enable corresponding changes of aesthetic appreciation is of particular interest for research as this will provide possibilities to modeling aesthetic appreciation for longer durations and from a dynamic perspective. The present paper refers to a recent two-step model ("the dynamical two-step-model of aesthetic appreciation"), dynamically adapting itself, which accounts for typical dynamics of aesthetic appreciation found in different research areas such as art history, philosophy and psychology. The first step assumes singular creative sources creating and establishing innovative material towards which, in a second step, people adapt by integrating it into their visual habits. This inherently leads to dynamic changes of the beholders' aesthetic appreciation.

  3. Perspectives of nonlinear dynamics

    International Nuclear Information System (INIS)

    Jackson, E.A.

    1985-03-01

    Four lectures were given weekly in October and November, 1984, and some of the ideas presented here will be of use in the future. First, a brief survey of the historical development of nonlinear dynamics since about 1890 was given, and then, a few topics were discussed in detail. The objective was to introduce some of many concepts and methods which are presently used for describing nonlinear dynamics. The symbiotic relationship between sciences of all types and mathematics, two main categories of the models describing nature, the method for describing the dynamics of a system, the idea of control parameters and topological dimension, the asymptotic properties of dynamics, abstract dynamics, the concept of embedding, singular perturbation theory, strange attractor, Fermi-Pasta-Ulam phenomena, an example of computer heuristics, the idea of elementary catastrophe theory and so on were explained. The logistic map is the simplest introduction to complex dynamics. The complicated dynamics is referred to as strange attractors. Two-dimensional maps are the highest dimensional maps commonly studied. These were discussed in detail. (Kako, I.)

  4. Operational Dynamic Configuration Analysis

    Science.gov (United States)

    Lai, Chok Fung; Zelinski, Shannon

    2010-01-01

    Sectors may combine or split within areas of specialization in response to changing traffic patterns. This method of managing capacity and controller workload could be made more flexible by dynamically modifying sector boundaries. Much work has been done on methods for dynamically creating new sector boundaries [1-5]. Many assessments of dynamic configuration methods assume the current day baseline configuration remains fixed [6-7]. A challenging question is how to select a dynamic configuration baseline to assess potential benefits of proposed dynamic configuration concepts. Bloem used operational sector reconfigurations as a baseline [8]. The main difficulty is that operational reconfiguration data is noisy. Reconfigurations often occur frequently to accommodate staff training or breaks, or to complete a more complicated reconfiguration through a rapid sequence of simpler reconfigurations. Gupta quantified a few aspects of airspace boundary changes from this data [9]. Most of these metrics are unique to sector combining operations and not applicable to more flexible dynamic configuration concepts. To better understand what sort of reconfigurations are acceptable or beneficial, more configuration change metrics should be developed and their distribution in current practice should be computed. This paper proposes a method to select a simple sequence of configurations among operational configurations to serve as a dynamic configuration baseline for future dynamic configuration concept assessments. New configuration change metrics are applied to the operational data to establish current day thresholds for these metrics. These thresholds are then corroborated, refined, or dismissed based on airspace practitioner feedback. The dynamic configuration baseline selection method uses a k-means clustering algorithm to select the sequence of configurations and trigger times from a given day of operational sector combination data. The clustering algorithm selects a simplified

  5. Dynamic training algorithm for dynamic neural networks

    International Nuclear Information System (INIS)

    Tan, Y.; Van Cauwenberghe, A.; Liu, Z.

    1996-01-01

    The widely used backpropagation algorithm for training neural networks based on the gradient descent has a significant drawback of slow convergence. A Gauss-Newton method based recursive least squares (RLS) type algorithm with dynamic error backpropagation is presented to speed-up the learning procedure of neural networks with local recurrent terms. Finally, simulation examples concerning the applications of the RLS type algorithm to identification of nonlinear processes using a local recurrent neural network are also included in this paper

  6. Living with Dynamic Concepts in Dynamic Environments

    DEFF Research Database (Denmark)

    Rehm, Matthias

    2003-01-01

    a dynamic perspective, concepts depend on different factors like the learning process, the environment, i.e. the situational setting. It is indispensable for an agent to create individual concepts that adhere to restrictions imposed by the environment and the society it is living in. It is shown...... that changes in the environment lead to changes in existing concepts and to establishing new ones with only a small irritation in the use of the old ones....

  7. Fluid dynamics transactions

    CERN Document Server

    Fiszdon, W

    1965-01-01

    Fluid Dynamics Transactions, Volume 2 compiles 46 papers on fluid dynamics, a subdiscipline of fluid mechanics that deals with fluid flow. The topics discussed in this book include developments in interference theory for aeronautical applications; diffusion from sources in a turbulent boundary layer; unsteady motion of a finite wing span in a compressible medium; and wall pressure covariance and comparison with experiment. The certain classes of non-stationary axially symmetric flows in magneto-gas-dynamics; description of the phenomenon of secondary flows in curved channels by means of co

  8. Advances in Dynamic Games

    CERN Document Server

    Breton, Michele

    2011-01-01

    This book focuses on various aspects of dynamic game theory, presenting state-of-the-art research and serving as a testament to the vitality and growth of the field of dynamic games and their applications. The selected contributions, written by experts in their respective disciplines, are outgrowths of presentations originally given at the 13th International Symposium of Dynamic Games and Applications held in WrocACaw. The book covers a variety of topics, ranging from theoretical developments in game theory and algorithmic methods to applications, examples, and analysis in fields as varied as

  9. Basic structural dynamics

    CERN Document Server

    Anderson, James C

    2012-01-01

    A concise introduction to structural dynamics and earthquake engineering Basic Structural Dynamics serves as a fundamental introduction to the topic of structural dynamics. Covering single and multiple-degree-of-freedom systems while providing an introduction to earthquake engineering, the book keeps the coverage succinct and on topic at a level that is appropriate for undergraduate and graduate students. Through dozens of worked examples based on actual structures, it also introduces readers to MATLAB, a powerful software for solving both simple and complex structural d

  10. High enthalpy gas dynamics

    CERN Document Server

    Rathakrishnan, Ethirajan

    2014-01-01

    This is an introductory level textbook which explains the elements of high temperature and high-speed gas dynamics. written in a clear and easy to follow style, the author covers all the latest developments in the field including basic thermodynamic principles, compressible flow regimes and waves propagation in one volume covers theoretical modeling of High Enthalpy Flows, with particular focus on problems in internal and external gas-dynamic flows, of interest in the fields of rockets propulsion and hypersonic aerodynamics High enthalpy gas dynamics is a compulsory course for aerospace engine

  11. Shadowing in dynamical systems

    CERN Document Server

    Pilyugin, Sergei Yu

    1999-01-01

    This book is an introduction to the theory of shadowing of approximate trajectories in dynamical systems by exact ones. This is the first book completely devoted to the theory of shadowing. It shows the importance of shadowing theory for both the qualitative theory of dynamical systems and the theory of numerical methods. Shadowing Methods allow us to estimate differences between exact and approximate solutions on infinite time intervals and to understand the influence of error terms. The book is intended for specialists in dynamical systems, for researchers and graduate students in the theory of numerical methods.

  12. Dynamics from diffraction

    International Nuclear Information System (INIS)

    Goodwin, Andrew L.; Tucker, Matthew G.; Cope, Elizabeth R.; Dove, Martin T.; Keen, David A.

    2006-01-01

    We explore the possibility that detailed dynamical information might be extracted from powder diffraction data. Our focus is a recently reported technique that employs statistical analysis of atomistic configurations to calculate dynamical properties from neutron total scattering data. We show that it is possible to access the phonon dispersion of low-frequency modes using such an approach, without constraining the results in terms of some pre-defined dynamical model. The high-frequency regions of the phonon spectrum are found to be less well preserved in the diffraction data

  13. Fundamentals of gas dynamics

    CERN Document Server

    Babu, V

    2014-01-01

    Fundamentals of Gas Dynamics, Second Edition isa comprehensively updated new edition and now includes a chapter on the gas dynamics of steam. It covers the fundamental concepts and governing equations of different flows, and includes end of chapter exercises based on the practical applications. A number of useful tables on the thermodynamic properties of steam are also included.Fundamentals of Gas Dynamics, Second Edition begins with an introduction to compressible and incompressible flows before covering the fundamentals of one dimensional flows and normal shock wav

  14. Stability of dynamical systems

    CERN Document Server

    Liao, Xiaoxin; Yu, P 0

    2007-01-01

    The main purpose of developing stability theory is to examine dynamic responses of a system to disturbances as the time approaches infinity. It has been and still is the object of intense investigations due to its intrinsic interest and its relevance to all practical systems in engineering, finance, natural science and social science. This monograph provides some state-of-the-art expositions of major advances in fundamental stability theories and methods for dynamic systems of ODE and DDE types and in limit cycle, normal form and Hopf bifurcation control of nonlinear dynamic systems.ʺ Presents

  15. Dynamics at the nanoscale

    International Nuclear Information System (INIS)

    Stoneham, A.M.; Gavartin, J.L.

    2007-01-01

    However fascinating structures may be at the nanoscale, time-dependent behaviour at the nanoscale has far greater importance. Some of the dynamics is random, with fluctuations controlling rate processes and making thermal ratchets possible. Some of the dynamics causes the transfer of energy, of signals, or of charge. Such transfers are especially efficiently controlled in biological systems. Other dynamical processes occur when we wish to control the nanoscale, e.g., to avoid local failures of gate dielectrics, or to manipulate structures by electronic excitation, to use spin manipulation in quantum information processing. Our prime purpose is to make clear the enormous range and variety of time-dependent nanoscale phenomena

  16. Theoretical Fluid Dynamics

    CERN Document Server

    Shivamoggi, Bhimsen K

    1998-01-01

    "Although there are many texts and monographs on fluid dynamics, I do not know of any which is as comprehensive as the present book. It surveys nearly the entire field of classical fluid dynamics in an advanced, compact, and clear manner, and discusses the various conceptual and analytical models of fluid flow." - Foundations of Physics on the first edition. Theoretical Fluid Dynamics functions equally well as a graduate-level text and a professional reference. Steering a middle course between the empiricism of engineering and the abstractions of pure mathematics, the author focuses

  17. Discrete Dynamics Lab

    Science.gov (United States)

    Wuensche, Andrew

    DDLab is interactive graphics software for creating, visualizing, and analyzing many aspects of Cellular Automata, Random Boolean Networks, and Discrete Dynamical Networks in general and studying their behavior, both from the time-series perspective — space-time patterns, and from the state-space perspective — attractor basins. DDLab is relevant to research, applications, and education in the fields of complexity, self-organization, emergent phenomena, chaos, collision-based computing, neural networks, content addressable memory, genetic regulatory networks, dynamical encryption, generative art and music, and the study of the abstract mathematical/physical/dynamical phenomena in their own right.

  18. Dynamic Systems and Control Engineering

    International Nuclear Information System (INIS)

    Kim, Jong Seok

    1994-02-01

    This book deals with introduction of dynamic system and control engineering, frequency domain modeling of dynamic system, temporal modeling of dynamic system, typical dynamic system and automatic control device, performance and stability of control system, root locus analysis, analysis of frequency domain dynamic system, design of frequency domain dynamic system, design and analysis of space, space of control system and digital control system such as control system design of direct digital and digitalization of consecutive control system.

  19. Dynamic Systems and Control Engineering

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong Seok

    1994-02-15

    This book deals with introduction of dynamic system and control engineering, frequency domain modeling of dynamic system, temporal modeling of dynamic system, typical dynamic system and automatic control device, performance and stability of control system, root locus analysis, analysis of frequency domain dynamic system, design of frequency domain dynamic system, design and analysis of space, space of control system and digital control system such as control system design of direct digital and digitalization of consecutive control system.

  20. Multidimensional high harmonic spectroscopy

    International Nuclear Information System (INIS)

    Bruner, Barry D; Soifer, Hadas; Shafir, Dror; Dudovich, Nirit; Serbinenko, Valeria; Smirnova, Olga

    2015-01-01

    High harmonic generation (HHG) has opened up a new frontier in ultrafast science where attosecond time resolution and Angstrom spatial resolution are accessible in a single measurement. However, reconstructing the dynamics under study is limited by the multiple degrees of freedom involved in strong field interactions. In this paper we describe a new class of measurement schemes for resolving attosecond dynamics, integrating perturbative nonlinear optics with strong-field physics. These approaches serve as a basis for multidimensional high harmonic spectroscopy. Specifically, we show that multidimensional high harmonic spectroscopy can measure tunnel ionization dynamics with high precision, and resolves the interference between multiple ionization channels. In addition, we show how multidimensional HHG can function as a type of lock-in amplifier measurement. Similar to multi-dimensional approaches in nonlinear optical spectroscopy that have resolved correlated femtosecond dynamics, multi-dimensional high harmonic spectroscopy reveals the underlying complex dynamics behind attosecond scale phenomena. (paper)

  1. Liquid Sloshing Dynamics

    Science.gov (United States)

    Ibrahim, Raouf A.

    2005-06-01

    The problem of liquid sloshing in moving or stationary containers remains of great concern to aerospace, civil, and nuclear engineers; physicists; designers of road tankers and ship tankers; and mathematicians. Beginning with the fundamentals of liquid sloshing theory, this book takes the reader systematically from basic theory to advanced analytical and experimental results in a self-contained and coherent format. The book is divided into four sections. Part I deals with the theory of linear liquid sloshing dynamics; Part II addresses the nonlinear theory of liquid sloshing dynamics, Faraday waves, and sloshing impacts; Part III presents the problem of linear and nonlinear interaction of liquid sloshing dynamics with elastic containers and supported structures; and Part IV considers the fluid dynamics in spinning containers and microgravity sloshing. This book will be invaluable to researchers and graduate students in mechanical and aeronautical engineering, designers of liquid containers, and applied mathematicians.

  2. Ansatz for dynamical hierarchies

    DEFF Research Database (Denmark)

    Rasmussen, S.; Baas, N.A.; Mayer, B.

    2001-01-01

    Complex, robust functionalities can be generated naturally in at least two ways: by the assembly of structures and by the evolution of structures. This work is concerned with spontaneous formation of structures. We define the notion of dynamical hierarchies in natural systems and show...... the importance of this particular kind of organization for living systems. We then define a framework that enables us to formulate, investigate, and manipulate such dynamical hierarchies. This framework allows us to simultaneously investigate different levels of description together with them interrelationship...... three. Formulating this system as a simple two-dimensional molecular dynamics (MD) lattice gas allows us within one dynamical system to demonstrate the successive emergence of two higher levels (three levels all together) of robust structures with associated properties. Second, we demonstrate how...

  3. Longitudinal beam dynamics

    International Nuclear Information System (INIS)

    Tecker, F

    2014-01-01

    The course gives a summary of longitudinal beam dynamics for both linear and circular accelerators. After discussing different types of acceleration methods and synchronism conditions, it focuses on the particle motion in synchrotrons

  4. Stochastic dynamics and irreversibility

    CERN Document Server

    Tomé, Tânia

    2015-01-01

    This textbook presents an exposition of stochastic dynamics and irreversibility. It comprises the principles of probability theory and the stochastic dynamics in continuous spaces, described by Langevin and Fokker-Planck equations, and in discrete spaces, described by Markov chains and master equations. Special concern is given to the study of irreversibility, both in systems that evolve to equilibrium and in nonequilibrium stationary states. Attention is also given to the study of models displaying phase transitions and critical phenomema both in thermodynamic equilibrium and out of equilibrium. These models include the linear Glauber model, the Glauber-Ising model, lattice models with absorbing states such as the contact process and those used in population dynamic and spreading of epidemic, probabilistic cellular automata, reaction-diffusion processes, random sequential adsorption and dynamic percolation. A stochastic approach to chemical reaction is also presented.The textbook is intended for students of ...

  5. Supervision and group dynamics

    DEFF Research Database (Denmark)

    Hansen, Søren; Jensen, Lars Peter

    2004-01-01

     An important aspect of the problem based and project organized study at Aalborg University is the supervision of the project groups. At the basic education (first year) it is stated in the curriculum that part of the supervisors' job is to deal with group dynamics. This is due to the experience...... that many students are having difficulties with practical issues such as collaboration, communication, and project management. Most supervisors either ignore this demand, because they do not find it important or they find it frustrating, because they do not know, how to supervise group dynamics...... as well as at Aalborg University. The first visible result has been participating supervisors telling us that the course has inspired them to try supervising group dynamics in the future. This paper will explore some aspects of supervising group dynamics as well as, how to develop the Aalborg model...

  6. Equivalent Dynamic Models.

    Science.gov (United States)

    Molenaar, Peter C M

    2017-01-01

    Equivalences of two classes of dynamic models for weakly stationary multivariate time series are discussed: dynamic factor models and autoregressive models. It is shown that exploratory dynamic factor models can be rotated, yielding an infinite set of equivalent solutions for any observed series. It also is shown that dynamic factor models with lagged factor loadings are not equivalent to the currently popular state-space models, and that restriction of attention to the latter type of models may yield invalid results. The known equivalent vector autoregressive model types, standard and structural, are given a new interpretation in which they are conceived of as the extremes of an innovating type of hybrid vector autoregressive models. It is shown that consideration of hybrid models solves many problems, in particular with Granger causality testing.

  7. Invitation to dynamical systems

    CERN Document Server

    Scheinerman, Edward R

    2012-01-01

    This text is designed for those who wish to study mathematics beyond linear algebra but are unready for abstract material. Rather than a theorem-proof-corollary exposition, it stresses geometry, intuition, and dynamical systems. 1996 edition.

  8. Transonic Dynamics Tunnel (TDT)

    Data.gov (United States)

    Federal Laboratory Consortium — The Transonic Dynamics Tunnel (TDT) is a continuous flow wind-tunnel facility capable of speeds up to Mach 1.2 at stagnation pressures up to one atmosphere. The TDT...

  9. Advances in soil dynamics

    DEFF Research Database (Denmark)

    Advances in Soil Dynamics, Volume 3, represents the culmination of the work undertaken by the Advances in Soil Dynamics Monograph Committee, PM-45-01, about 15 years ago to summarize important developments in this field over the last 35 years. When this project was initiated, the main goal...... was to abridge major strides made in the general area of soil dynamics during the sixties, seventies, and eighties. However, by about the mid-nineties soil dynamics research in the US and much of the developed world had come to a virtual standstill. Although significant progress was made prior to the mid......-nineties, we still do not have a sound fundamental knowledge of soil-machine and soil-plant interactions. It is the hope of the editors that these three volumes will provide a ready reference for much needed future research in this area....

  10. based dynamic voltage restorer

    African Journals Online (AJOL)

    HOD

    operation due to presence of increased use of nonlinear loads (computers, microcontrollers ... simulations of a dynamic voltage restorer (DVR) was achieved using MATLAB/Simulink. ..... using Discrete PWM generator, then the IGBT inverter.

  11. Peri-dynamics

    International Nuclear Information System (INIS)

    Littlewood, D.

    2015-01-01

    Peri-dynamics, a nonlocal extension of continuum mechanics, is a natural framework for capturing constitutive response and modelling pervasive material failure and fracture. Unlike classical approaches incorporating partial derivatives, the peri-dynamic governing equations utilise integral expressions that remain valid in the presence of discontinuities such as cracks. The mathematical theory of peri-dynamics unifies the mechanics of continuous media, cracks, and discrete particles. The result is a consistent framework for capturing a wide range of constitutive responses, including inelasticity, in combination with robust material failure laws. Peri-dynamics has been implemented in a number of computational simulation codes, including the open source code Peridigm and the Sierra/SolidMechanics analysis code at Sandia National Laboratories. (author)

  12. Mercury's Dynamic Magnetosphere

    Science.gov (United States)

    Imber, S. M.

    2018-05-01

    The global dynamics of Mercury's magnetosphere will be discussed, focussing on observed asymmetries in the magnetotail and on the precipitation of particles of magnetospheric origin onto the nightside planetary surface.

  13. Market Squid Population Dynamics

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains population dynamics data on paralarvae, juvenile and adult market squid collected off California and the US Pacific Northwest. These data were...

  14. Gun Dynamics Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Gun Dynamics Laboratory is a research multi-task facility, which includes two firing bays, a high bay area and a second floor laboratory space. The high bay area...

  15. Dual Dynamic Programming - DDP

    International Nuclear Information System (INIS)

    Velasquez Bermudez, Jesus M

    1998-01-01

    Objections are presented to the mathematical formulation of the denominated Dual Dynamic programming-PDD that is the theoretical base of several computational model available for the optimal formulation of interconnected hydrothermal systems

  16. Controlling Uncertain Dynamical Systems

    Indian Academy of Sciences (India)

    Author Affiliations. N Ananthkrishnan1 Rashi Bansal2. Head, CAE Analysis & Design Zeus Numerix Pvt Ltd. M-03, SINE, IIT Bombay Powai Mumbai 400076, India. MTech (Aerospace Engineering) with specialization in Dynamics & Control from IIT Bombay.

  17. Instantaneous and dynamical decoherence

    Science.gov (United States)

    Polonyi, Janos

    2018-04-01

    Two manifestations of decoherence, called instantaneous and dynamical, are investigated. The former reflects the suppression of the interference between the components of the current state while the latter reflects that within the initial state. These types of decoherence are computed in the case of the Brownian motion and the harmonic and anharmonic oscillators within the semiclassical approximation. A remarkable phenomenon, namely the opposite orientation of the time arrow of the dynamical variables compared to that of the quantum fluctuations generates a double exponential time dependence of the dynamical decoherence in the presence of a harmonic force. For the weakly anharmonic oscillator the dynamical decoherence is found to depend in a singular way on the amount of the anharmonicity.

  18. Structural dynamic modification

    Indian Academy of Sciences (India)

    and stiffness matrices) andaor modal parameters, in order to acquire some ... For the above reasons, another modification approach is presented here ... The data necessary to solve the direct problem are dynamic behaviour of the original.

  19. Dynamics of interstellar matter

    International Nuclear Information System (INIS)

    Kahn, F.D.

    1975-01-01

    A review of the dynamics of interstellar matter is presented, considering the basic equations of fluid flow, plane waves, shock waves, spiral structure, thermal instabilities and early star cocoons. (B.R.H.)

  20. Fish population dynamics

    National Research Council Canada - National Science Library

    Gulland, J. A

    1977-01-01

    This book describes how the dynamics of fish populations can be analysed in terms of the factors affecting their rates of growth, mortality and reproduction, with particular emphasis on the effects of fishing...