Excited state non-adiabatic dynamics of N-methylpyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study

Energy Technology Data Exchange (ETDEWEB)

Wu, Guorong [National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023 (China); Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Neville, Simon P. [Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5 (Canada); Schalk, Oliver [National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Department of Physics, AlbaNova University Center, Stockholm University, Roslagstullsbacken 21, 106 91 Stockholm (Sweden); Sekikawa, Taro [Department of Applied Physics, Hokkaido University, Kita-13 Nishi-8, Kita-ku, Sapporo 060-8628 (Japan); Ashfold, Michael N. R. [School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom); Worth, Graham A. [School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Stolow, Albert, E-mail: astolow@uottawa.ca [National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5 (Canada); Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5 (Canada)

2016-01-07

The dynamics of N-methylpyrrole following excitation at wavelengths in the range 241.5-217.0 nm were studied using a combination of time-resolved photoelectron spectroscopy (TRPES), ab initio quantum dynamics calculations using the multi-layer multi-configurational time-dependent Hartree method, as well as high-level photoionization cross section calculations. Excitation at 241.5 and 236.2 nm results in population of the A{sub 2}(πσ{sup ∗}) state, in agreement with previous studies. Excitation at 217.0 nm prepares the previously neglected B{sub 1}(π3p{sub y}) Rydberg state, followed by prompt internal conversion to the A{sub 2}(πσ{sup ∗}) state. In contrast with the photoinduced dynamics of pyrrole, the lifetime of the wavepacket in the A{sub 2}(πσ{sup ∗}) state was found to vary with excitation wavelength, decreasing by one order of magnitude upon tuning from 241.5 nm to 236.2 nm and by more than three orders of magnitude when excited at 217.0 nm. The order of magnitude difference in lifetimes measured at the longer excitation wavelengths is attributed to vibrational excitation in the A{sub 2}(πσ{sup ∗}) state, facilitating wavepacket motion around the potential barrier in the N–CH{sub 3} dissociation coordinate.

Excited state non-adiabatic dynamics of N-methylpyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study

International Nuclear Information System (INIS)

Wu, Guorong; Neville, Simon P.; Schalk, Oliver; Sekikawa, Taro; Ashfold, Michael N. R.; Worth, Graham A.; Stolow, Albert

2016-01-01

The dynamics of N-methylpyrrole following excitation at wavelengths in the range 241.5-217.0 nm were studied using a combination of time-resolved photoelectron spectroscopy (TRPES), ab initio quantum dynamics calculations using the multi-layer multi-configurational time-dependent Hartree method, as well as high-level photoionization cross section calculations. Excitation at 241.5 and 236.2 nm results in population of the A 2 (πσ ∗ ) state, in agreement with previous studies. Excitation at 217.0 nm prepares the previously neglected B 1 (π3p y ) Rydberg state, followed by prompt internal conversion to the A 2 (πσ ∗ ) state. In contrast with the photoinduced dynamics of pyrrole, the lifetime of the wavepacket in the A 2 (πσ ∗ ) state was found to vary with excitation wavelength, decreasing by one order of magnitude upon tuning from 241.5 nm to 236.2 nm and by more than three orders of magnitude when excited at 217.0 nm. The order of magnitude difference in lifetimes measured at the longer excitation wavelengths is attributed to vibrational excitation in the A 2 (πσ ∗ ) state, facilitating wavepacket motion around the potential barrier in the N–CH 3 dissociation coordinate

A new methodology for measuring time correlations and excite states of atoms and nuclei

International Nuclear Information System (INIS)

Cavalcante, M.A.

1989-01-01

A system for measuring time correlation of physical phenomena events in the range of 10 -7 to 10 5 sec is proposed, and his results presented. This system, is based on a sequential time scale which is controlled by a precision quartz oscillator; the zero time of observation is set by means of a JK Flip-Flop, which is operated by a negative transition of pulse in coincidence with the pulse from a detector which marks the time zero of the event (precedent pulse). This electronic system (named digital chronoanalizer) was used in the measurement of excited states of nuclei as well as for the determination of time fluctuations in physical phenomena, such as the time lag in a halogen Geiger counter and is the measurement of the 60 KeV excited state of N P 237 . (author)

Excited states 2

CERN Document Server

Lim, Edward C

2013-01-01

Excited States, Volume 2 is a collection of papers that deals with molecules in the excited states. The book describes the geometries of molecules in the excited electronic states. One paper describes the geometries of a diatomic molecule and of polyatomic molecules; it also discusses the determination of the many excited state geometries of molecules with two, three, or four atoms by techniques similar to diatomic spectroscopy. Another paper introduces an ordered theory related to excitons in pure and mixed molecular crystals. This paper also presents some experimental data such as those invo

Time evolution of one-dimensional gapless models from a domain wall initial state: stochastic Loewner evolution continued?

International Nuclear Information System (INIS)

Calabrese, Pasquale; Hagendorf, Christian; Doussal, Pierre Le

2008-01-01

We study the time evolution of quantum one-dimensional gapless systems evolving from initial states with a domain wall. We generalize the path integral imaginary time approach that together with boundary conformal field theory allows us to derive the time and space dependence of general correlation functions. The latter are explicitly obtained for the Ising universality class, and the typical behavior of one- and two-point functions is derived for the general case. Possible connections with the stochastic Loewner evolution are discussed and explicit results for one-point time dependent averages are obtained for generic κ for boundary conditions corresponding to stochastic Loewner evolution. We use this set of results to predict the time evolution of the entanglement entropy and obtain the universal constant shift due to the presence of a domain wall in the initial state

Nonlinear stability of spin-flip excitations

International Nuclear Information System (INIS)

Arunasalam, V.

1975-01-01

A rather complete discussion of the nonlinear electrodynamic behavior of a negative-temperature spin system is presented. The method presented here is based on a coupled set of master equations, one describing the time evolution of the photon (i.e., the spin-flip excitation) distribution function and the other describing the time evolution of the particle distribution function. It is found that the initially unstable (i.e., growing) spin-flip excitations grow to such a large amplitude that their nonlinear reaction on the particle distribution function becomes important. It is then shown that the initially totally inverted two-level spin system evolves rapidly (through this nonlinear photon-particle coupling) towards a quasilinear steady state where the populations of the spin-up and the spin-down states are equal to each other. Explicit expressions for the time taken to reach this quasilinear steady state and the energy in the spin-flip excitations at this state are also presented

Application of the Real-Time Time-Dependent Density Functional Theory to Excited-State Dynamics of Molecules and 2D Materials

Science.gov (United States)

Miyamoto, Yoshiyuki; Rubio, Angel

2018-04-01

We review our recent developments in the ab initio simulation of excited-state dynamics within the framework of time-dependent density functional theory (TDDFT). Our targets range from molecules to 2D materials, although the methods are general and can be applied to any other finite and periodic systems. We discuss examples of excited-state dynamics obtained by real-time TDDFT coupled with molecular dynamics (MD) and the Ehrenfest approximation, including photoisomerization in molecules, photoenhancement of the weak interatomic attraction of noble gas atoms, photoenhancement of the weak interlayer interaction of 2D materials, pulse-laser-induced local bond breaking of adsorbed atoms on 2D sheets, modulation of UV light intensity by graphene nanoribbons at terahertz frequencies, and collision of high-speed ions with the 2D material to simulate the images taken by He ion microscopy. We illustrate how the real-time TDDFT approach is useful for predicting and understanding non-equilibrium dynamics in condensed matter. We also discuss recent developments that address the excited-state dynamics of systems out of equilibrium and future challenges in this fascinating field of research.

Time evolution of gibbs states for an anharmonic lattice

Energy Technology Data Exchange (ETDEWEB)

Marchioro, C; Pellegrinotti, A; Suhov, Y [Camerino Univ. (Italy). Istituto di Matematica; Pulvirenti, M [L' Aquila Univ. (Italy). Istituto di Matematica; Rome Univ. (Italy). Istituto di Matematica)

1979-01-01

In this paper we study the time evolution of a regular class of states of an infinite classical system of anharmonic oscillators. The conditional probabilities are investigated and an explicit form for these is given.

Excited state kinetics of anthracene-bridge-aniline intramolecular exciplexes

DEFF Research Database (Denmark)

Thyrhaug, Erling; Hammershøj, Peter; Kjær, Kasper Skov

2014-01-01

excited anthracene state (LE) and an excited state complex (exciplex, EP) in non-polar solvents. The kinetics of the excited state processes were established in decalin from the time-resolved emission, and was shown to be strongly influenced by an electron-transfer state (ET). For quantitative studies...

Excited states v.6

CERN Document Server

Lim, Edward C

1982-01-01

Excited States, Volume 6 is a collection of papers that discusses the excited states of molecules. The first paper discusses the linear polyene electronic structure and potential surfaces, considering both the theoretical and experimental approaches in such electronic states. This paper also reviews the theory of electronic structure and cites some experimental techniques on polyene excitations, polyene spectroscopic phenomenology, and those involving higher states of polyenes and their triplet states. Examples of these experimental studies of excited states involve the high-resolution one-pho

Time evolution of gibbs states for an anharmonic lattice

International Nuclear Information System (INIS)

Marchioro, C.; Pellegrinotti, A.; Suhov, Y.; Pulvirenti, M.; Rome Univ.

1979-01-01

In this paper we study the time evolution of a regular class of states of an infinite classical system of anharmonic oscillators. The conditional probabilities are investigated and an explicit form for these is given. (orig.) [de

Excited states

CERN Document Server

Lim, Edward C

1974-01-01

Excited States, Volume I reviews radiationless transitions, phosphorescence microwave double resonance through optical spectra in molecular solids, dipole moments in excited states, luminescence of polar molecules, and the problem of interstate interaction in aromatic carbonyl compounds. The book discusses the molecular electronic radiationless transitions; the double resonance techniques and the relaxation mechanisms involving the lowest triplet state of aromatic compounds; as well as the optical spectra and relaxation in molecular solids. The text also describes dipole moments and polarizab

Excited states of ReO4-: A comprehensive time-dependent relativistic density functional theory study

Science.gov (United States)

Xu, Wenhua; Ma, Jianyi; Peng, Daoling; Zou, Wenli; Liu, Wenjian; Staemmler, Volker

2009-02-01

The perrhenate anion, ReO4-, is taken as a showcase of heavy transition metal complexes, to examine the performance of time-dependent relativistic density functional linear response theory for electronic excitations, which is based on a newly proposed exact two-component Hamiltonian resulting from the symmetrized elimination of the small component. In total 30 scalar and 63 spinor excited states are investigated and the results are grossly in good agreement with those by the singles and doubles coupled-cluster linear response theory. It is found that only a few scalar states of 3T1 and 3T2 symmetries are split significantly by the spin-orbit coupling, whereas only those excited states involving the Rydberg-type virtual orbital are affected by the solvent effects. The nature of the optical absorption spectra is also highlighted.

Excited states of ReO4-: A comprehensive time-dependent relativistic density functional theory study

International Nuclear Information System (INIS)

Xu Wenhua; Ma Jianyi; Peng Daoling; Zou Wenli; Liu Wenjian; Staemmler, Volker

2009-01-01

The perrhenate anion, ReO 4 - , is taken as a showcase of heavy transition metal complexes, to examine the performance of time-dependent relativistic density functional linear response theory for electronic excitations, which is based on a newly proposed exact two-component Hamiltonian resulting from the symmetrized elimination of the small component. In total 30 scalar and 63 spinor excited states are investigated and the results are grossly in good agreement with those by the singles and doubles coupled-cluster linear response theory. It is found that only a few scalar states of 3 T 1 and 3 T 2 symmetries are split significantly by the spin-orbit coupling, whereas only those excited states involving the Rydberg-type virtual orbital are affected by the solvent effects. The nature of the optical absorption spectra is also highlighted

Time evolution of quenched state and correlation to glassy effects

International Nuclear Information System (INIS)

Kilic, K.; Kilic, A.; Altinkok, A.; Yetis, H.; Cetin, O.; Durust, Y.

2005-01-01

In this work, dynamic changes generated by the driving current were studied in superconducting bulk polycrystalline YBCO sample via transport relaxation measurements (V-t curves). The evolution of nonlinear V-t curves was interpreted in terms of the formation of resistive and nonresistive flow channels and the spatial reorganization of the transport current in a multiply connected network of weak-link structure. The dynamic re-organization of driving current could cause an enhancement or suppression in the superconducting order parameter due to the magnitude of the driving current and coupling strength of weak-link structure along with the chemical and anisotropic states of the sample as the time proceeds. A nonzero voltage decaying with time, correlated to the quenched state, was recorded when the magnitude of initial driving current is reduced to a finite value. It was found that, after sufficiently long waiting time, the evolution of the quenched state could result in a superconducting state, depending on the magnitude of the driving current and temperature. We showed that the decays in voltage over time are consistent with an exponential time dependence which is related to the glassy state. Further, the effect of doping of organic material Bis dimethyl-glyoximato Copper (II) to YBCO could be monitored apparently via the comparison of the V-t curves corresponding to doped and undoped YBCO samples

Giant resonances on excited states

International Nuclear Information System (INIS)

Besold, W.; Reinhard, P.G.; Toepffer, C.

1984-01-01

We derive modified RPA equations for small vibrations about excited states. The temperature dependence of collective excitations is examined. The formalism is applied to the ground state and the first excited state of 90 Zr in order to confirm a hypothesis which states that not only the ground state but every excited state of a nucleus has a giant resonance built upon it. (orig.)

Faraday waves under time-reversed excitation.

Science.gov (United States)

Pietschmann, Dirk; Stannarius, Ralf; Wagner, Christian; John, Thomas

2013-03-01

Do parametrically driven systems distinguish periodic excitations that are time mirrors of each other? Faraday waves in a Newtonian fluid are studied under excitation with superimposed harmonic wave forms. We demonstrate that the threshold parameters for the stability of the ground state are insensitive to a time inversion of the driving function. This is a peculiarity of some dynamic systems. The Faraday system shares this property with standard electroconvection in nematic liquid crystals [J. Heuer et al., Phys. Rev. E 78, 036218 (2008)]. In general, time inversion of the excitation affects the asymptotic stability of a parametrically driven system, even when it is described by linear ordinary differential equations. Obviously, the observed symmetry has to be attributed to the particular structure of the underlying differential equation system. The pattern selection of the Faraday waves above threshold, on the other hand, discriminates between time-mirrored excitation functions.

Time evolution of the Wigner function in the entangled-state representation

International Nuclear Information System (INIS)

Fan Hongyi

2002-01-01

For quantum-mechanical entangled states we introduce the entangled Wigner operator in the entangled-state representation. We derive the time evolution equation of the entangled Wigner operator . The trace product rule for entangled Wigner functions is also obtained

Low-lying excited states by constrained DFT

Science.gov (United States)

Ramos, Pablo; Pavanello, Michele

2018-04-01

Exploiting the machinery of Constrained Density Functional Theory (CDFT), we propose a variational method for calculating low-lying excited states of molecular systems. We dub this method eXcited CDFT (XCDFT). Excited states are obtained by self-consistently constraining a user-defined population of electrons, Nc, in the virtual space of a reference set of occupied orbitals. By imposing this population to be Nc = 1.0, we computed the first excited state of 15 molecules from a test set. Our results show that XCDFT achieves an accuracy in the predicted excitation energy only slightly worse than linear-response time-dependent DFT (TDDFT), but without incurring into problems of variational collapse typical of the more commonly adopted ΔSCF method. In addition, we selected a few challenging processes to test the limits of applicability of XCDFT. We find that in contrast to TDDFT, XCDFT is capable of reproducing energy surfaces featuring conical intersections (azobenzene and H3) with correct topology and correct overall energetics also away from the intersection. Venturing to condensed-phase systems, XCDFT reproduces the TDDFT solvatochromic shift of benzaldehyde when it is embedded by a cluster of water molecules. Thus, we find XCDFT to be a competitive method among single-reference methods for computations of excited states in terms of time to solution, rate of convergence, and accuracy of the result.

Dynamic modification of the fragmentation of COq+ excited states generated with high-order harmonics

International Nuclear Information System (INIS)

Cao, W.; De, S.; Singh, K. P.; Chen, S.; Laurent, G.; Ray, D.; Ben-Itzhak, I.; Cocke, C. L.; Schoeffler, M. S.; Belkacem, A.; Osipov, T.; Rescigno, T.; Alnaser, A. S.; Bocharova, I. A.; Zherebtsov, S.; Kling, M. F.; Litvinyuk, I. V.

2010-01-01

The dynamic process of fragmentation of CO q+ excited states is investigated using a pump-probe approach. EUV radiation (32-48 eV) generated by high-order harmonics was used to ionize and excite CO molecules and a time-delayed infrared (IR) pulse (800 nm) was used to influence the evolution of the dissociating multichannel wave packet. Two groups of states, separable experimentally by their kinetic-energy release (KER), are populated by the EUV and lead to C + -O + fragmentation: direct double ionization of the neutral molecule and fragmentation of the cation leading to C + -O*, followed by autoionization of O*. The IR pulse was found to modify the KER of the latter group in a delay-dependent way which is explained with a model calculation.

Ultrafast excited state relaxation in long-chain polyenes

International Nuclear Information System (INIS)

Antognazza, Maria Rosa; Lueer, Larry; Polli, Dario; Christensen, Ronald L.; Schrock, Richard R.; Lanzani, Guglielmo; Cerullo, Giulio

2010-01-01

Graphical abstract: Excited state dynamics of a long-chain polyene studied by femtosecond pump-probe spectroscopy. - Abstract: We present a comprehensive study, by femtosecond pump-probe spectroscopy, of excited state dynamics in a polyene that approaches the infinite chain limit. By excitation with sub-10-fs pulses resonant with the 0-0 S 0 → S 2 transition, we observe rapid loss of stimulated emission from the bright excited state S 2 , followed by population of the hot S 1 state within 150 fs. Vibrational cooling of S 1 takes place within 500 fs and is followed by decay back to S 0 with 1 ps time constant. By excitation with excess vibrational energy we also observe the ultrafast formation of a long-living absorption, that is assigned to the triplet state generated by singlet fission.

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.

Benchmarks for electronically excited states: Time-dependent density functional theory and density functional theory based multireference configuration interaction

DEFF Research Database (Denmark)

Silva-Junior, Mario R.; Schreiber, Marko; Sauer, Stephan P. A.

2008-01-01

Time-dependent density functional theory (TD-DFT) and DFT-based multireference configuration interaction (DFT/MRCI) calculations are reported for a recently proposed benchmark set of 28 medium-sized organic molecules. Vertical excitation energies, oscillator strengths, and excited-state dipole...

How many atoms get excited when they decay?

DEFF Research Database (Denmark)

Blocher, Philip Daniel; Mølmer, Klaus

2017-01-01

We analyse the time evolution of a two-level system prepared in a superposition of its ground state and radiatively unstable excited state. We show that by choosing appropriate means of detection of the radiated field, we can steer the evolution of the emitter and herald its preparation in the fu...

Time-dependent theory of Raman scattering for systems with several excited electronic states: Application to a H+3 model system

International Nuclear Information System (INIS)

Heather, R.; Metiu, H.

1989-01-01

The time-dependent formulation of Raman scattering theory is used to study how nonadiabatic interactions affect the Raman spectrum of a model H + 3 system, which has two excited electronic states. We start with a formula derived by Heller which gives the Raman scattering cross section as the Fourier transform (over time) of a time-dependent overlap integral. The latter is calculated with a method proposed by Fleck, Morris, and Feit, and extended to curve crossing by Alvarellos and Metiu. In performing these calculations we are especially interested in displaying effects typical of systems having more than one upper state. If the incident laser populates two electronic states there are several ways (i.e., excite to state one and emit from state two, excite to state one, and emit from state one, etc.) by which the Raman process can reach a given final state, and this leads to quantum interference. This interference is manifested in the Raman cross section as approximate selection rules controlling which final states can be reached through the Raman process. These selection rules depend on the relative orientation of the transition dipoles that radiatively couple the ground electronic state with the excited electronic states. The magnitude of the nonadiabatic contribution to the Raman emission, e.g., the contribution from absorbing to state one and emitting from state two, can be determined from the polarization dependence of the Raman emission if the transition dipoles have neither parallel nor antiparallel relative orientation

Excited-state density functional theory

International Nuclear Information System (INIS)

Harbola, Manoj K; Hemanadhan, M; Shamim, Md; Samal, P

2012-01-01

Starting with a brief introduction to excited-state density functional theory, we present our method of constructing modified local density approximated (MLDA) energy functionals for the excited states. We show that these functionals give accurate results for kinetic energy and exchange energy compared to the ground state LDA functionals. Further, with the inclusion of GGA correction, highly accurate total energies for excited states are obtained. We conclude with a brief discussion on the further direction of research that include the construction of correlation energy functional and exchange potential for excited states.

Time evolution and decay of an excited atom in a weak electric field

International Nuclear Information System (INIS)

Wang, J.B.

1996-01-01

A Mathematica notebook for describing the time evolution and decay of the hydrogen n=2 states in the presence of a weak external electric field is presented. The work involves (1) solving a set of differential equations coupled by the Hamiltonian of the external electric field and (2) deriving a set of formulas for a complete description of the polarization state of the emitted photons. It is demonstrated how problems with such complexity can be treated with ease and in an error-free manner by using symbolic software such as Mathematica. copyright 1996 American Institute of Physics

Role of excited state solvent fluctuations on time-dependent fluorescence Stokes shift

Energy Technology Data Exchange (ETDEWEB)

Li, Tanping, E-mail: tanping@lsu.edu, E-mail: revatik@lsu.edu; Kumar, Revati, E-mail: tanping@lsu.edu, E-mail: revatik@lsu.edu [Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)

2015-11-07

We explore the connection between the solvation dynamics of a chromophore upon photon excitation and equilibrium fluctuations of the solvent. Using molecular dynamics simulations, fluorescence Stokes shift for the tryptophan in Staphylococcus nuclease was examined using both nonequilibrium calculations and linear response theory. When the perturbed and unperturbed surfaces exhibit different solvent equilibrium fluctuations, the linear response approach on the former surface shows agreement with the nonequilibrium process. This agreement is excellent when the perturbed surface exhibits Gaussian statistics and qualitative in the case of an isomerization induced non-Gaussian statistics. However, the linear response theory on the unperturbed surface breaks down even in the presence of Gaussian fluctuations. Experiments also provide evidence of the connection between the excited state solvent fluctuations and the total fluorescence shift. These observations indicate that the equilibrium statistics on the excited state surface characterize the relaxation dynamics of the fluorescence Stokes shift. Our studies specifically analyze the Gaussian fluctuations of the solvent in the complex protein environment and further confirm the role of solvent fluctuations on the excited state surface. The results are consistent with previous investigations, found in the literature, of solutes dissolved in liquids.

Classicalization times of parametrically amplified 'Schroedinger cat' states coupled to phase-sensitive reservoirs

International Nuclear Information System (INIS)

Dodonov, V.V.; Valverde, C.; Souza, L.S.; Baseia, B.

2011-01-01

The exact Wigner function of a parametrically excited quantum oscillator in a phase-sensitive amplifying/attenuating reservoir is found for initial even/odd coherent states. Studying the evolution of negativity of the Wigner function we show the difference between the 'initial positivization time' (IPT), which is inversely proportional to the square of the initial size of the superposition, and the 'final positivization time' (FPT), which does not depend on this size. Both these times can be made arbitrarily long in maximally squeezed high-temperature reservoirs. Besides, we find the conditions when some (small) squeezing can exist even after the Wigner function becomes totally positive. -- Highlights: → We study parametric excitation of a quantum oscillator in phase-sensitive baths. → Exact time-dependent Wigner function for initial even/odd coherent states is found. → The evolution of negativity of Wigner function is compared with the squeezing dynamics. → The difference between initial and final 'classicalization times' is emphasized. → Both these times can be arbitrarily long for rigged reservoirs at infinite temperature.

A coarse grained description of time evolution: Irreversible state reduction and time-energy relation

International Nuclear Information System (INIS)

Bonifacio, R.; Milan Univ.

1983-05-01

We show that a proper coarse-grained description of time evolution leads to a finite difference equation with step tau for the density operator. This implies state reduction to the diagonal form in the energy representation and a quasi ergodic behaviour of quantum mechanical ensemble averages. An intrinsic time-energy relation tauΔE>=(h/2π)/2 is proposed, and its equivalence to a time quantization is discussed. (author)

Electron impact excitation of xenon from the metastable state to the excited states

Energy Technology Data Exchange (ETDEWEB)

Jiang Jun; Dong Chenzhong; Xie Luyou; Zhou Xiaoxin [College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Wang Jianguo [Institute of Applied Physics and Computational Mathematic, Beijing 100088 (China)], E-mail: dongcz@nwnu.edu.cn

2008-12-28

The electron impact excitation cross sections from the lowest metastable state 5p{sup 5}6sJ = 2 to the six lowest excited states of the 5p{sup 5}6p configuration of xenon are calculated systematically by using the fully relativistic distorted wave method. In order to discuss the effects of target state descriptions on the electron impact excitation cross sections, two correlation models are used to describe the target states based on the multiconfiguration Dirac-Fock (MCDF) method. It is found that the correlation effects play a very important role in low energy impact. For high energy impact, however, the cross sections are not sensitive to the description of the target states, but many more partial waves must be included.

Sequential double excitations from linear-response time-dependent density functional theory

Energy Technology Data Exchange (ETDEWEB)

Mosquera, Martín A.; Ratner, Mark A.; Schatz, George C., E-mail: g-schatz@northwestern.edu [Department of Chemistry, Northwestern University, 2145 Sheridan Rd., Evanston, Illinois 60208 (United States); Chen, Lin X. [Department of Chemistry, Northwestern University, 2145 Sheridan Rd., Evanston, Illinois 60208 (United States); Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Ave., Lemont, Illinois 60439 (United States)

2016-05-28

Traditional UV/vis and X-ray spectroscopies focus mainly on the study of excitations starting exclusively from electronic ground states. However there are many experiments where transitions from excited states, both absorption and emission, are probed. In this work we develop a formalism based on linear-response time-dependent density functional theory to investigate spectroscopic properties of excited states. We apply our model to study the excited-state absorption of a diplatinum(II) complex under X-rays, and transient vis/UV absorption of pyrene and azobenzene.

A multiconfigurational time-dependent Hartree-Fock method for excited electronic states. I. General formalism and application to open-shell states.

Science.gov (United States)

Miranda, R P; Fisher, A J; Stella, L; Horsfield, A P

2011-06-28

The solution of the time-dependent Schrödinger equation for systems of interacting electrons is generally a prohibitive task, for which approximate methods are necessary. Popular approaches, such as the time-dependent Hartree-Fock (TDHF) approximation and time-dependent density functional theory (TDDFT), are essentially single-configurational schemes. TDHF is by construction incapable of fully accounting for the excited character of the electronic states involved in many physical processes of interest; TDDFT, although exact in principle, is limited by the currently available exchange-correlation functionals. On the other hand, multiconfigurational methods, such as the multiconfigurational time-dependent Hartree-Fock (MCTDHF) approach, provide an accurate description of the excited states and can be systematically improved. However, the computational cost becomes prohibitive as the number of degrees of freedom increases, and thus, at present, the MCTDHF method is only practical for few-electron systems. In this work, we propose an alternative approach which effectively establishes a compromise between efficiency and accuracy, by retaining the smallest possible number of configurations that catches the essential features of the electronic wavefunction. Based on a time-dependent variational principle, we derive the MCTDHF working equation for a multiconfigurational expansion with fixed coefficients and specialise to the case of general open-shell states, which are relevant for many physical processes of interest.

Rydberg energies using excited state density functional theory

International Nuclear Information System (INIS)

Cheng, C.-L.; Wu Qin; Van Voorhis, Troy

2008-01-01

We utilize excited state density functional theory (eDFT) to study Rydberg states in atoms. We show both analytically and numerically that semilocal functionals can give quite reasonable Rydberg energies from eDFT, even in cases where time dependent density functional theory (TDDFT) fails catastrophically. We trace these findings to the fact that in eDFT the Kohn-Sham potential for each state is computed using the appropriate excited state density. Unlike the ground state potential, which typically falls off exponentially, the sequence of excited state potentials has a component that falls off polynomially with distance, leading to a Rydberg-type series. We also address the rigorous basis of eDFT for these systems. Perdew and Levy have shown using the constrained search formalism that every stationary density corresponds, in principle, to an exact stationary state of the full many-body Hamiltonian. In the present context, this means that the excited state DFT solutions are rigorous as long as they deliver the minimum noninteracting kinetic energy for the given density. We use optimized effective potential techniques to show that, in some cases, the eDFT Rydberg solutions appear to deliver the minimum kinetic energy because the associated density is not pure state v-representable. We thus find that eDFT plays a complementary role to constrained DFT: The former works only if the excited state density is not the ground state of some potential while the latter applies only when the density is a ground state density.

Derivation of the RPA (Random Phase Approximation) Equation of ATDDFT (Adiabatic Time Dependent Density Functional Ground State Response Theory) from an Excited State Variational Approach Based on the Ground State Functional.

Science.gov (United States)

Ziegler, Tom; Krykunov, Mykhaylo; Autschbach, Jochen

2014-09-09

The random phase approximation (RPA) equation of adiabatic time dependent density functional ground state response theory (ATDDFT) has been used extensively in studies of excited states. It extracts information about excited states from frequency dependent ground state response properties and avoids, thus, in an elegant way, direct Kohn-Sham calculations on excited states in accordance with the status of DFT as a ground state theory. Thus, excitation energies can be found as resonance poles of frequency dependent ground state polarizability from the eigenvalues of the RPA equation. ATDDFT is approximate in that it makes use of a frequency independent energy kernel derived from the ground state functional. It is shown in this study that one can derive the RPA equation of ATDDFT from a purely variational approach in which stationary states above the ground state are located using our constricted variational DFT (CV-DFT) method and the ground state functional. Thus, locating stationary states above the ground state due to one-electron excitations with a ground state functional is completely equivalent to solving the RPA equation of TDDFT employing the same functional. The present study is an extension of a previous work in which we demonstrated the equivalence between ATDDFT and CV-DFT within the Tamm-Dancoff approximation.

Excited-state molecular photoionization dynamics

International Nuclear Information System (INIS)

Pratt, S.T.

1995-01-01

This review presents a survey of work using resonance-enhanced multiphoton ionization and double-resonance techniques to study excited-state photoionization dynamics in molecules. These techniques routinely provide detail and precision that are difficult to achieve in single-photon ionization from the ground state. The review not only emphasizes new aspects of photoionization revealed in the excited-state experiments but also shows how the excited-state techniques can provide textbook illustrations of some fundamental mechanisms in molecular photoionization dynamics. Most of the examples are confined to diatomic molecules. (author)

Excited states in biological systems

International Nuclear Information System (INIS)

Cilento, G.; Zinner, K.; Bechara, E.J.H.; Duran, N.; Baptista, R.C. de; Shimizu, Y.; Augusto, O.; Faljoni-Alario, A.; Vidigal, C.C.C.; Oliveira, O.M.M.F.; Haun, M.

1979-01-01

Some aspects of bioluminescence related to bioenergetics are discussed: 1. chemical generation of excited species, by means of two general processes: electron transference and cyclic - and linear peroxide cleavage; 2. biological systems capable of generating excited states and 3. biological functions of these states, specially the non-emissive ones (tripletes). The production and the role of non-emissive excited states in biological systems are analysed, the main purpose of the study being the search for non-emissive states. Experiences carried out in biological systems are described; results and conclusions are given. (M.A.) [pt

Application of an excited state LDA exchange energy functional for the calculation of transition energy of atoms within time-independent density functional theory

Energy Technology Data Exchange (ETDEWEB)

Shamim, Md; Harbola, Manoj K, E-mail: sami@iitk.ac.i, E-mail: mkh@iitk.ac.i [Department of Physics, Indian Institute of Technology, Kanpur 208 016 (India)

2010-11-14

Transition energies of a new class of excited states (two-gap systems) of various atoms are calculated in time-independent density functional formalism by using a recently proposed local density approximation exchange energy functional for excited states. It is shown that the excitation energies calculated with this functional compare well with those calculated with exact exchange theories.

Application of an excited state LDA exchange energy functional for the calculation of transition energy of atoms within time-independent density functional theory

International Nuclear Information System (INIS)

Shamim, Md; Harbola, Manoj K

2010-01-01

Transition energies of a new class of excited states (two-gap systems) of various atoms are calculated in time-independent density functional formalism by using a recently proposed local density approximation exchange energy functional for excited states. It is shown that the excitation energies calculated with this functional compare well with those calculated with exact exchange theories.

Self-excited vibration control for axially fast excited beam by a time delay state feedback

International Nuclear Information System (INIS)

Hamdi, Mustapha; Belhaq, Mohamed

2009-01-01

This work examines the control of self-excited vibration of a simply-supported beam subjected to an axially high-frequency excitation. The investigation of the resonant cases are not considered in this paper. The control is implemented via a corrective position feedback with time delay. The objective of this control is to eliminate the undesirable self-excited vibrations with an appropriate choice of parameters. The issue of stability is also addressed in this paper. Using the technique of direct partition of motion, the dynamic of discretized equations is separated into slow and fast components. The multiple scales method is then performed on the slow dynamic to obtain a slow flow for the amplitude and phase. Analysis of this slow flow provides analytical approximations locating regions in parameters space where undesirable self-excited vibration can be eliminated. A numerical study of these regions is performed on the original discretized system and compared to the analytical prediction showing a good agreement.

Electronically excited negative ion resonant states in chloroethylenes

Energy Technology Data Exchange (ETDEWEB)

Khvostenko, O.G., E-mail: khv@mail.ru; Lukin, V.G.; Tuimedov, G.M.; Khatymova, L.Z.; Kinzyabulatov, R.R.; Tseplin, E.E.

2015-02-15

Highlights: • Several novel dissociative negative ion channels were revealed in chloroethylenes. • The electronically excited resonant states were recorded in all chloroethylenes under study. • The states were assigned to the inter-shell types, but not to the core-excited Feshbach one. - Abstract: The negative ion mass spectra of the resonant electron capture by molecules of 1,1-dichloroethylene, 1,2-dichloroethylene-cis, 1,2-dichloroethylene-trans, trichloroethylene and tetrachloroethylene have been recorded in the 0–12 eV range of the captured electron energy using static magnetic sector mass spectrometer modified for operation in the resonant electron capture regime. As a result, several novel low-intensive dissociation channels were revealed in the compounds under study. Additionally, the negative ion resonant states were recorded at approximately 3–12 eV, mostly for the first time. These resonant states were assigned to the electronically excited resonances of the inter-shell type by comparing their energies with those of the parent neutral molecules triplet and singlet electronically excited states known from the energy-loss spectra obtained by previous studies.

Time evolution of multiple quantum coherences in NMR

International Nuclear Information System (INIS)

Sanchez, Claudia M.; Pastawski, Horacio M.; Levstein, Patricia R.

2007-01-01

In multiple quantum NMR, individual spins become correlated with one another over time through their dipolar couplings. In this way, the usual Zeeman selection rule can be overcome and forbidden transitions can be excited. Experimentally, these multiple quantum coherences (MQC) are formed by the application of appropriate sequences of radio frequency pulses that force the spins to act collectively. 1 H spin coherences of even order up to 16 were excited in a polycrystalline sample of ferrocene (C 5 H 5 ) 2 Fe and up to 32 in adamantane (C 10 H 16 ) and their evolutions studied in different conditions: (a) under the natural dipolar Hamiltonian, H ZZ (free evolution) and with H ZZ canceled out by (b) time reversion or (c) with the MREV8 sequence. The results show that when canceling H ZZ the coherences decay with characteristic times (τ c ∼200 μs), which are more than one order of magnitude longer than those under free evolution (τ c ∼10 μs). In addition, it is observed that with both MREV8 and time reversion sequences, the higher the order of the coherence (larger number of correlated spins) the faster the speed of degradation, as it happens during the evolution with H ZZ . In both systems, it is observed that the sequence of time reversion of the dipolar Hamiltonian preserves coherences for longer times than MREV8

Linear-scaling quantum mechanical methods for excited states.

Science.gov (United States)

Yam, ChiYung; Zhang, Qing; Wang, Fan; Chen, GuanHua

2012-05-21

The poor scaling of many existing quantum mechanical methods with respect to the system size hinders their applications to large systems. In this tutorial review, we focus on latest research on linear-scaling or O(N) quantum mechanical methods for excited states. Based on the locality of quantum mechanical systems, O(N) quantum mechanical methods for excited states are comprised of two categories, the time-domain and frequency-domain methods. The former solves the dynamics of the electronic systems in real time while the latter involves direct evaluation of electronic response in the frequency-domain. The localized density matrix (LDM) method is the first and most mature linear-scaling quantum mechanical method for excited states. It has been implemented in time- and frequency-domains. The O(N) time-domain methods also include the approach that solves the time-dependent Kohn-Sham (TDKS) equation using the non-orthogonal localized molecular orbitals (NOLMOs). Besides the frequency-domain LDM method, other O(N) frequency-domain methods have been proposed and implemented at the first-principles level. Except one-dimensional or quasi-one-dimensional systems, the O(N) frequency-domain methods are often not applicable to resonant responses because of the convergence problem. For linear response, the most efficient O(N) first-principles method is found to be the LDM method with Chebyshev expansion for time integration. For off-resonant response (including nonlinear properties) at a specific frequency, the frequency-domain methods with iterative solvers are quite efficient and thus practical. For nonlinear response, both on-resonance and off-resonance, the time-domain methods can be used, however, as the time-domain first-principles methods are quite expensive, time-domain O(N) semi-empirical methods are often the practical choice. Compared to the O(N) frequency-domain methods, the O(N) time-domain methods for excited states are much more mature and numerically stable, and

Ultrafast excited-state dynamics of 2,5-dimethylpyrrole.

Science.gov (United States)

Yang, Dongyuan; Min, Yanjun; Chen, Zhichao; He, Zhigang; Yuan, Kaijun; Dai, Dongxu; Yang, Xueming; Wu, Guorong

2018-04-17

The ultrafast excited-state dynamics of 2,5-dimethylpyrrole following excitation at wavelengths in the range of 265.7-216.7 nm is studied using the time-resolved photoelectron imaging method. It is found that excitation at longer wavelengths (265.7-250.2 nm) results in the population of the S1(1πσ*) state, which decays out of the photoionization window in about 90 fs. At shorter pump wavelengths (242.1-216.7 nm), the assignments are less clear-cut. We tentatively assign the initially photoexcited state(s) to the 1π3p Rydberg state(s) which has lifetimes of 159 ± 20, 125 ± 15, 102 ± 10 and 88 ± 10 fs for the pump wavelengths of 242.1, 238.1, 232.6 and 216.7 nm, respectively. Internal conversion to the S1(1πσ*) state represents at most a minor decay channel. The methyl substitution effects on the decay dynamics of the excited states of pyrrole are also discussed. Methyl substitution on the pyrrole ring seems to enhance the direct internal conversion from the 1π3p Rydberg state to the ground state, while methyl substitution on the N atom has less influence and the internal conversion to the S1(πσ*) state represents a main channel.

Effects of optical pumping in the photo-excitation of organic triplet states

International Nuclear Information System (INIS)

Lin, Tien-Sung; Yang, Tran-Chin; Sloop, David J.

2013-01-01

Highlights: • High electron spin polarization (ESP) was observed in pentacene triplets at room temperature. • The high ESP is transfer to the surrounding nuclear spin by optical pumping in zero-field (ZF). • The ZF transition frequencies and their line width depend on the laser pumping rate. • The spin–lattice relaxation times of the nuclear system are evaluated. - Abstract: Upon the application of laser and microwave pulses, non-zero magnetic moment of a photo-excited triplet state of organic molecules is generated in zero-field (ZF). The time evolution of the transient magnetic moments can be measured by free induction decay (FID) in ZF. The observed ZF spectra become broadened and ZF transition shifted to lower frequencies when the repetition rate of laser excitation is increased, which are attributed to the optical pumping of nuclear polarization (ONP) effect and the associated nuclear spin lattice relaxation processes. The observed ONP effect is discussed in terms of the local field effect and spin diffusion processes in optical pumping

Effects of optical pumping in the photo-excitation of organic triplet states

Energy Technology Data Exchange (ETDEWEB)

Lin, Tien-Sung, E-mail: lin@wustl.edu; Yang, Tran-Chin; Sloop, David J.

2013-08-30

Highlights: • High electron spin polarization (ESP) was observed in pentacene triplets at room temperature. • The high ESP is transfer to the surrounding nuclear spin by optical pumping in zero-field (ZF). • The ZF transition frequencies and their line width depend on the laser pumping rate. • The spin–lattice relaxation times of the nuclear system are evaluated. - Abstract: Upon the application of laser and microwave pulses, non-zero magnetic moment of a photo-excited triplet state of organic molecules is generated in zero-field (ZF). The time evolution of the transient magnetic moments can be measured by free induction decay (FID) in ZF. The observed ZF spectra become broadened and ZF transition shifted to lower frequencies when the repetition rate of laser excitation is increased, which are attributed to the optical pumping of nuclear polarization (ONP) effect and the associated nuclear spin lattice relaxation processes. The observed ONP effect is discussed in terms of the local field effect and spin diffusion processes in optical pumping.

Excitation of autoionizing states of helium by 100 keV proton impact: II. Excitation cross sections and mechanisms of excitation

Energy Technology Data Exchange (ETDEWEB)

Godunov, A.L. [Department of Physics, Tulane University, New Orleans, LA 70118-5698 (United States); Ivanov, P.B.; Schipakov, V.A. [Troitsk Institute of Innovation and Fusion Research Troitsk, Moscow region, 142092 (Russian Federation); Moretto-Capelle, P.; Bordenave-Montesquieu, D.; Bordenave-Montesquieu, A. [Laboratoire Collisions, Agregats, Reactivite, IRSAMC, UMR 5589, CNRS-Universite Paul Sabatier, 31062 Toulouse Cedex (France)

2000-03-14

Mechanisms of two-electron excitation of the (2s{sup 2}){sup 1} S, (2p{sup 2} ){sup 1} D and (2s2p){sup 1} P autoionizing states of helium are studied both experimentally and theoretically. It is shown that an explicit introduction of a kinematic factor, with a process-specific phase leads to a productive parametrization of experimental cross sections of ionization, allowing one to extract cross sections of excitation of autoionizing states. Using a new fitting procedure together with the proposed parametrization made it possible to obtain the excitation cross sections and magnetic sublevel population from electron spectra as well as, for the first time, to resolve the contribution of resonance and interference components to resonance profiles. Interference with direct ionization is shown to contribute significantly into resonance formation even for backward ejection angles. We demonstrate theoretically that the excitation cross sections thus extracted from experimental electron spectra hold information about the interaction of autoionizing states with an adjacent continuum. (author)

Unitarity and the time evolution of quantum mechanical states

International Nuclear Information System (INIS)

Kabir, P.K.; Pilaftsis, A.

1996-01-01

The basic requirement that, in quantum theory, the time evolution of any state is determined by the action of a unitary operator, is shown to be the underlying cause for certain open-quote open-quote exact close-quote close-quote results that have recently been reported about the time dependence of transition rates in quantum theory. Departures from exponential decay, including the open-quote open-quote quantum Zeno effect,close-quote close-quote as well as a theorem by Khalfin about the ratio of reciprocal transition rates, are shown to follow directly from such considerations. At sufficiently short times, unitarity requires that reciprocity must hold, independent of whether T invariance is valid. If T invariance does not hold, unitarity restricts the form of possible time dependence of reciprocity ratios. copyright 1996 The American Physical Society

Tight-binding approximations to time-dependent density functional theory — A fast approach for the calculation of electronically excited states

Energy Technology Data Exchange (ETDEWEB)

Rüger, Robert, E-mail: rueger@scm.com [Scientific Computing & Modelling NV, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands); Department of Theoretical Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands); Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Linnéstr. 2, 04103 Leipzig (Germany); Lenthe, Erik van [Scientific Computing & Modelling NV, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands); Heine, Thomas [Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Linnéstr. 2, 04103 Leipzig (Germany); Visscher, Lucas [Department of Theoretical Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam (Netherlands)

2016-05-14

We propose a new method of calculating electronically excited states that combines a density functional theory based ground state calculation with a linear response treatment that employs approximations used in the time-dependent density functional based tight binding (TD-DFTB) approach. The new method termed time-dependent density functional theory TD-DFT+TB does not rely on the DFTB parametrization and is therefore applicable to systems involving all combinations of elements. We show that the new method yields UV/Vis absorption spectra that are in excellent agreement with computationally much more expensive TD-DFT calculations. Errors in vertical excitation energies are reduced by a factor of two compared to TD-DFTB.

Spectroscopic Diagnosis of Excited-State Aromaticity: Capturing Electronic Structures and Conformations upon Aromaticity Reversal.

Science.gov (United States)

Oh, Juwon; Sung, Young Mo; Hong, Yongseok; Kim, Dongho

2018-03-06

Aromaticity, the special energetic stability derived from cyclic [4 n + 2]π-conjugated electronic structures, has been the topic of intense interest in chemistry because it plays a critical role in rationalizing molecular stability, reactivity, and physical/chemical properties. Recently, the pioneering work by Colin Baird on aromaticity reversal, postulating that aromatic (antiaromatic) character in the ground state reverses to antiaromatic (aromatic) character in the lowest excited triplet state, has attracted much scientific attention. The completely reversed aromaticity in the excited state provides direct insight into understanding the photophysical/chemical properties of photoactive materials. In turn, the application of aromatic molecules to photoactive materials has led to numerous studies revealing this aromaticity reversal. However, most studies of excited-state aromaticity have been based on the theoretical point of view. The experimental evaluation of aromaticity in the excited state is still challenging and strenuous because the assessment of (anti)aromaticity with conventional magnetic, energetic, and geometric indices is difficult in the excited state, which practically restricts the extension and application of the concept of excited-state aromaticity. Time-resolved optical spectroscopies can provide a new and alternative avenue to evaluate excited-state aromaticity experimentally while observing changes in the molecular features in the excited states. Time-resolved optical spectroscopies take advantage of ultrafast laser pulses to achieve high time resolution, making them suitable for monitoring ultrafast changes in the excited states of molecular systems. This can provide valuable information for understanding the aromaticity reversal. This Account presents recent breakthroughs in the experimental assessment of excited-state aromaticity and the verification of aromaticity reversal with time-resolved optical spectroscopic measurements. To

Photoionization dynamics of excited molecular states

International Nuclear Information System (INIS)

Dehmer, J.L.; O'Halloran, M.A.; Tomkins, F.S.; Dehmer, P.M.; Pratt, S.T.

1987-01-01

Resonance Enhanced Multiphoton Ionization (REMPI) utilizes tunable dye lasers to ionize an atom or molecule by first preparing an excited state by multiphoton absorption and then ionizing that state before it can decay. This process is highly selective with respect to both the initial and resonant intermediate states of the target, and it can be extremely sensitive. In addition, the products of the REMPI process can be detected as needed by analyzing the resulting electrons, ions, fluorescence, or by additional REMPI. This points to a number of opportunities for exploring excited state physics and chemistry at the quantum-state-specific level. Here we will first give a brief overview of the large variety of experimental approaches to excited state phenomena made possible by REMPI. Then we will examine in more detail, recent studies of the three photon resonant, four photon (3 + 1) ionization of H 2 via the C 'PI/sup u/ state. Strong non-Franck-Condon behavior in the photoelectron spectra of this nominally simple Rydberg state has led to the examination of a variety of dynamical mechanisms. Of these, the role of doubly excited autoionizing states now seems decisive. Progress on photoelectron studies of autoionizing states in H 2 , excited in a (2 + 1) REMPI process via the E, F 1 Σ/sub g/ + will also be briefly discussed. 26 refs., 7 figs

Self-Consistent Optimization of Excited States within Density-Functional Tight-Binding.

Science.gov (United States)

Kowalczyk, Tim; Le, Khoa; Irle, Stephan

2016-01-12

We present an implementation of energies and gradients for the ΔDFTB method, an analogue of Δ-self-consistent-field density functional theory (ΔSCF) within density-functional tight-binding, for the lowest singlet excited state of closed-shell molecules. Benchmarks of ΔDFTB excitation energies, optimized geometries, Stokes shifts, and vibrational frequencies reveal that ΔDFTB provides a qualitatively correct description of changes in molecular geometries and vibrational frequencies due to excited-state relaxation. The accuracy of ΔDFTB Stokes shifts is comparable to that of ΔSCF-DFT, and ΔDFTB performs similarly to ΔSCF with the PBE functional for vertical excitation energies of larger chromophores where the need for efficient excited-state methods is most urgent. We provide some justification for the use of an excited-state reference density in the DFTB expansion of the electronic energy and demonstrate that ΔDFTB preserves many of the properties of its parent ΔSCF approach. This implementation fills an important gap in the extended framework of DFTB, where access to excited states has been limited to the time-dependent linear-response approach, and affords access to rapid exploration of a valuable class of excited-state potential energy surfaces.

The mechanisms of Excited states in enzymes

DEFF Research Database (Denmark)

Petersen, Frederic Nicolas Rønne; Bohr, Henrik

2010-01-01

Enzyme catalysis is studied on the basis of excited state processes, which are of electronic, vibrational and thermal nature. The ways of achieving the excited state, such as photo-absorption and ligand binding, are discussed and exemplified by various cases of enzymes.......Enzyme catalysis is studied on the basis of excited state processes, which are of electronic, vibrational and thermal nature. The ways of achieving the excited state, such as photo-absorption and ligand binding, are discussed and exemplified by various cases of enzymes....

Controlling excited-state contamination in nucleon matrix elements

Energy Technology Data Exchange (ETDEWEB)

Yoon, Boram; Gupta, Rajan; Bhattacharya, Tanmoy; Engelhardt, Michael; Green, Jeremy; Joó, Bálint; Lin, Huey-Wen; Negele, John; Orginos, Kostas; Pochinsky, Andrew; Richards, David; Syritsyn, Sergey; Winter, Frank

2016-06-01

We present a detailed analysis of methods to reduce statistical errors and excited-state contamination in the calculation of matrix elements of quark bilinear operators in nucleon states. All the calculations were done on a 2+1 flavor ensemble with lattices of size $32^3 \\times 64$ generated using the rational hybrid Monte Carlo algorithm at $a=0.081$~fm and with $M_\\pi=312$~MeV. The statistical precision of the data is improved using the all-mode-averaging method. We compare two methods for reducing excited-state contamination: a variational analysis and a two-state fit to data at multiple values of the source-sink separation $t_{\\rm sep}$. We show that both methods can be tuned to significantly reduce excited-state contamination and discuss their relative advantages and cost-effectiveness. A detailed analysis of the size of source smearing used in the calculation of quark propagators and the range of values of $t_{\\rm sep}$ needed to demonstrate convergence of the isovector charges of the nucleon to the $t_{\\rm sep} \\to \\infty $ estimates is presented.

Excited state Intramolecular Proton Transfer in Anthralin

DEFF Research Database (Denmark)

Møller, Søren; Andersen, Kristine B.; Spanget-Larsen, Jens

1998-01-01

Quantum chemical calculations performed on anthralin (1,8-dihydroxy-9(10H)-anthracenone) predict the possibility of an excited-state intramolecular proton transfer process. Fluorescence excitation and emission spectra of the compound dissolved in n-hexane at ambient temperature results in an unus......Quantum chemical calculations performed on anthralin (1,8-dihydroxy-9(10H)-anthracenone) predict the possibility of an excited-state intramolecular proton transfer process. Fluorescence excitation and emission spectra of the compound dissolved in n-hexane at ambient temperature results......, associated with an excited-state intramolecular proton transfer process....

Speed of quantum evolution of entangled two qubits states: Local vs. global evolution

International Nuclear Information System (INIS)

Curilef, S; Zander, C; Plastino, A R

2008-01-01

There is a lower bound for the 'speed' of quantum evolution as measured by the time needed to reach an orthogonal state. We show that, for two-qubits systems, states saturating the quantum speed limit tend to exhibit a small amount of local evolution, as measured by the fidelity between the initial and final single qubit states after the time τ required by the composite system to reach an orthogonal state. Consequently, a trade-off between the speed of global evolution and the amount of local evolution seems to be at work.

Excited-state imaging of cold atoms

NARCIS (Netherlands)

Sheludko, D.V.; Bell, S.C.; Vredenbregt, E.J.D.; Scholten, R.E.; Deshmukh, P.C.; Chakraborty, P.; Williams, J.F.

2007-01-01

We have investigated state-selective diffraction contrast imaging (DCI) of cold 85Rb atoms in the first excited (52P3/2) state. Excited-state DCI requires knowledge of the complex refractive index of the atom cloud, which was calculated numerically using a semi-classical model. The Autler-Townes

Coulomb excitation of neutron-rich $^{134-136}$Sn isotopes

CERN Multimedia

We propose to study excited states in the isotopes $^{134,136}$Sn by $\\gamma$-ray spectroscopy following "safe" Coulomb excitation. The experiment aims to investigate the evolution of quadrupole collectivity beyond the magic shell closure at N = 82 by the determination of B(E2) values and electric quadrupole moments $\\mathcal{Q}_2$. Recent shell-model calculations using realistic interactions predict possible enhanced collectivity in neutron-rich regions. Evidence for this could be obtained by this experiment. Furthermore, the currently unknown excitation energies of the 2$^+_{1}$ and 4$^+_{1}$ states in $^{136}$Sn will be measured for the first time.

Electronic Excitations in Solution: The Interplay between State Specific Approaches and a Time-Dependent Density Functional Theory Description.

Science.gov (United States)

Guido, Ciro A; Jacquemin, Denis; Adamo, Carlo; Mennucci, Benedetta

2015-12-08

We critically analyze the performances of continuum solvation models when coupled to time-dependent density functional theory (TD-DFT) to predict solvent effects on both absorption and emission energies of chromophores in solution. Different polarization schemes of the polarizable continuum model (PCM), such as linear response (LR) and three different state specific (SS) approaches, are considered and compared. We show the necessity of introducing a SS model in cases where large electron density rearrangements are involved in the excitations, such as charge-transfer transitions in both twisted and quadrupolar compounds, and underline the very delicate interplay between the selected polarization method and the chosen exchange-correlation functional. This interplay originates in the different descriptions of the transition and ground/excited state multipolar moments by the different functionals. As a result, the choice of both the DFT functional and the solvent polarization scheme has to be consistent with the nature of the studied electronic excitation.

Optical studies of multiply excited states

International Nuclear Information System (INIS)

Mannervik, S.

1989-01-01

Optical studies of multiply-excited states are reviewed with emphasis on emission spectroscopy. From optical measurements, properties such as excitation energies, lifetimes and autoionization widths can be determined with high accuracy, which constitutes a challenge for modern computational methods. This article mainly covers work on two-, three- and four-electron systems, but also sodium-like quartet systems. Furthermore, some comments are given on bound multiply-excited states in negative ions. Fine structure effects on transition wavelengths and lifetimes (autoionization) are discussed. In particular, the most recent experimental and theoretical studies of multiply-excited states are covered. Some remaining problems, which require further attention, are discussed in more detail. (orig.) With 228 refs

Entanglement entropy of excited states

International Nuclear Information System (INIS)

Alba, Vincenzo; Fagotti, Maurizio; Calabrese, Pasquale

2009-01-01

We study the entanglement entropy of a block of contiguous spins in excited states of spin chains. We consider the XY model in a transverse field and the XXZ Heisenberg spin chain. For the latter, we developed a numerical application of the algebraic Bethe ansatz. We find two main classes of states with logarithmic and extensive behavior in the dimension of the block, characterized by the properties of excitations of the state. This behavior can be related to the locality properties of the Hamiltonian having a given state as the ground state. We also provide several details of the finite size scaling

Picosecond spectral relaxation of curcumin excited state in toluene–alcohol mixtures

Energy Technology Data Exchange (ETDEWEB)

Saini, R.K.; Das, K., E-mail: kaustuv@rrcat.gov.in

2013-12-15

Excited state photophysics of Curcumin in a binary solvent mixture of toluene and five different alcohols (Methanol, Ethanol, 1-Propanol, 1-Butanol and 1-Octanol) are compared with an instrument time resolution of ∼40 ps. As the alcohol mole-fraction is varied from zero to unity, the observed trends in the fluorescence quantum yield and lifetime of the pigment in toluene–alcohol mixtures changes significantly in going from Methanol to 1-Octanol. This is attributed to the different degree of modulation of the non-radiative rates associated with the excited state intermolecular H bonding between the pigment and the alcohol. Fluorescence decays taken at the red edge of the emission spectrum started to show measurable rise times (200–30 ps) the magnitude of which decreased gradually with increasing alcohol mole-fraction. As a consequence the solvation times in the binary mixture were observed to slow down considerably at certain solvent compositions compared to that in neat alcohol. However, in toluene-1-Octanol mixture, the rise times and corresponding solvation times did not show a dependence on the 1-Octanol mole-fraction. The observed results suggest that viscosity, polarity and hydrogen bonding property of the alcohol solvent plays an important role in the excited state processes of the pigment in toluene–alcohol mixture. -- Highlights: • Excited state photophysics of Curcumin in a binary solvent mixture of toluene and five different alcohols were studied. • The observed trends in the fluorescence properties are attributed to intermolecular H bonding between the pigment and the alcohol. • Except 1-Octanol, the average solvation times of the pigment were observed to depend upon alcohol mole-fraction. • Viscosity, polarity and hydrogen bonding play an important role in the excited state processes of the pigment.

Picosecond spectral relaxation of curcumin excited state in toluene–alcohol mixtures

International Nuclear Information System (INIS)

Saini, R.K.; Das, K.

2013-01-01

Excited state photophysics of Curcumin in a binary solvent mixture of toluene and five different alcohols (Methanol, Ethanol, 1-Propanol, 1-Butanol and 1-Octanol) are compared with an instrument time resolution of ∼40 ps. As the alcohol mole-fraction is varied from zero to unity, the observed trends in the fluorescence quantum yield and lifetime of the pigment in toluene–alcohol mixtures changes significantly in going from Methanol to 1-Octanol. This is attributed to the different degree of modulation of the non-radiative rates associated with the excited state intermolecular H bonding between the pigment and the alcohol. Fluorescence decays taken at the red edge of the emission spectrum started to show measurable rise times (200–30 ps) the magnitude of which decreased gradually with increasing alcohol mole-fraction. As a consequence the solvation times in the binary mixture were observed to slow down considerably at certain solvent compositions compared to that in neat alcohol. However, in toluene-1-Octanol mixture, the rise times and corresponding solvation times did not show a dependence on the 1-Octanol mole-fraction. The observed results suggest that viscosity, polarity and hydrogen bonding property of the alcohol solvent plays an important role in the excited state processes of the pigment in toluene–alcohol mixture. -- Highlights: • Excited state photophysics of Curcumin in a binary solvent mixture of toluene and five different alcohols were studied. • The observed trends in the fluorescence properties are attributed to intermolecular H bonding between the pigment and the alcohol. • Except 1-Octanol, the average solvation times of the pigment were observed to depend upon alcohol mole-fraction. • Viscosity, polarity and hydrogen bonding play an important role in the excited state processes of the pigment

Characterization of weakly excited final states by shakedown spectroscopy of laser-excited potassium

International Nuclear Information System (INIS)

Schulz, J.; Heinaesmaeki, S.; Aksela, S.; Aksela, H.; Sankari, R.; Rander, T.; Lindblad, A.; Bergersen, H.; Oehrwall, G.; Svensson, S.; Kukk, E.

2006-01-01

3p shakedown spectra of laser excited potassium atoms as well as direct 3p photoemission of ground state potassium have been studied. These two excitation schemes lead to the same final states and thereby provide a good basis for a detailed study of the 3p 5 (4s3d) 1 configurations of singly ionized potassium and the photoemission processes leading to these configurations. The comparison of direct photoemission from the ground state and conjugate shakedown spectra from 4p 1/2 laser excited potassium made it possible to experimentally determine the character of final states that are only weakly excited in the direct photoemission but have a much higher relative intensity in the shakedown spectrum. Based on considerations of angular momentum and parity conservation the excitation scheme of the final states can be understood

Formation of Bonded Exciplex in the Excited States of Dicyanoanthracene-Pyridine System : Time Dependent Density Functional Theory Study

NARCIS (Netherlands)

Setiawan, D.; Sethio, D.; Martoprawiro, M.A.; Filatov, M.; Gaol, FL; Nguyen, QV

2012-01-01

Strong quenching of fluorescence was recently observed in pyridine solutions of 9,10-dicyanoanthracene chromophore. It was hypothesized that quenching may be attributed to the formation of bound charge transfer complexes in the excited states of the molecules. In this work, using time-dependent

Critical Assessment of Time-Dependent Density Functional Theory for Excited States of Open-Shell Systems: II. Doublet-Quartet Transitions.

Science.gov (United States)

Li, Zhendong; Liu, Wenjian

2016-06-14

Compared with closed-shell systems, open-shell systems place three additional challenges to time-dependent density functional theory (TD-DFT) for electronically excited states: (a) the spin-contamination problem is a serious issue; (b) the exchange-correlation (XC) kernel may be numerically instable; and (c) the single-determinant description of open-shell ground states readily becomes energetically instable. Confined to flip-up single excitations, the spin-contamination problem can largely be avoided by using the spin-flip TD-DFT (SF-TD-DFT) formalism, provided that a noncollinear XC kernel is employed. As for the numerical instabilities associated with such a kernel, only an ad hoc scheme has been proposed so far, viz., the ALDA0 kernel, which amounts to setting the divergent components (arising from density gradients and kinetic energy density) simply to zero. The ground-state instability problem can effectively be avoided by introducing the Tamm-Dancoff approximation (TDA) to TD-DFT. Therefore, on a general basis, the SF-TDA/ALDA0 Ansatz is so far the only promising means within the TD-DFT framework for flip-up single excitations of open-shell systems. To assess systematically the performance of SF-TDA/ALDA0, in total 61 low-lying quartet excited states of the benchmark set of 11 small radicals [J. Chem. Theory Comput. 2016, 12, 238] are investigated with various XC functionals. Taking the MRCISD+Q (multireference configuration interaction with singles and doubles plus the Davidson correction) results as benchmark, it is found that the mean absolute errors of SF-TDA/ALDA0 with the SAOP (statistical averaging of model orbital potentials), global hybrid, and range-separated hybrid functionals are in the range of 0.2-0.4 eV. This is in line not only with the typical accuracy of TD-DFT for singlet and triplet excited states of closed-shell systems but also with the gross accuracy of spin-adapted TD-DFT for spin-conserving excited states of open-shell systems.

Spatial evolution of quantum mechanical states

Science.gov (United States)

Christensen, N. D.; Unger, J. E.; Pinto, S.; Su, Q.; Grobe, R.

2018-02-01

The time-dependent Schrödinger equation is solved traditionally as an initial-time value problem, where its solution is obtained by the action of the unitary time-evolution propagator on the quantum state that is known at all spatial locations but only at t = 0. We generalize this approach by examining the spatial evolution from a state that is, by contrast, known at all times t, but only at one specific location. The corresponding spatial-evolution propagator turns out to be pseudo-unitary. In contrast to the real energies that govern the usual (unitary) time evolution, the spatial evolution can therefore require complex phases associated with dynamically relevant solutions that grow exponentially. By introducing a generalized scalar product, for which the spatial generator is Hermitian, one can show that the temporal integral over the probability current density is spatially conserved, in full analogy to the usual norm of the state, which is temporally conserved. As an application of the spatial propagation formalism, we introduce a spatial backtracking technique that permits us to reconstruct any quantum information about an atom from the ionization data measured at a detector outside the interaction region.

Sub-50 fs excited state dynamics of 6-chloroguanine upon deep ultraviolet excitation.

Science.gov (United States)

Mondal, Sayan; Puranik, Mrinalini

2016-05-18

The photophysical properties of natural nucleobases and their respective nucleotides are ascribed to the sub-picosecond lifetime of their first singlet states in the UV-B region (260-350 nm). Electronic transitions of the ππ* type, which are stronger than those in the UV-B region, lie at the red edge of the UV-C range (100-260 nm) in all isolated nucleobases. The lowest energetic excited states in the UV-B region of nucleobases have been investigated using a plethora of experimental and theoretical methods in gas and solution phases. The sub-picosecond lifetime of these molecules is not a general attribute of all nucleobases but specific to the five primary nucleobases and a few xanthine and methylated derivatives. To determine the overall UV photostability, we aim to understand the effect of more energetic photons lying in the UV-C region on nucleobases. To determine the UV-C initiated photophysics of a nucleobase system, we chose a halogen substituted purine, 6-chloroguanine (6-ClG), that we had investigated previously using resonance Raman spectroscopy. We have performed quantitative measurements of the resonance Raman cross-section across the Bb absorption band (210-230 nm) and constructed the Raman excitation profiles. We modeled the excitation profiles using Lee and Heller's time-dependent theory of resonance Raman intensities to extract the initial excited state dynamics of 6-ClG within 30-50 fs after photoexcitation. We found that imidazole and pyrimidine rings of 6-ClG undergo expansion and contraction, respectively, following photoexcitation to the Bb state. The amount of distortions of the excited state structure from that of the ground state structure is reflected by the total internal reorganization energy that is determined at 112 cm(-1). The contribution of the inertial component of the solvent response towards the total reorganization energy was obtained at 1220 cm(-1). In addition, our simulation also yields an instantaneous response of the first

Particle hole excitations coupled to complex states in heavy-ion collisions

International Nuclear Information System (INIS)

Jolos, R.V.; Schmidt, R.

1982-01-01

The excitation of uncorrelated 1p-1h states in one nucleus due to the action of the time-dependent mean field of the other nucleus was studied earlier. No statistical assumptions or average procedures were made. Such a mechanism can be responsible for an appreciable excitation of the two nuclei during the short approach phase of the reaction (E* approximately> 100 MeV). The reversibility of the equations of motion leads to a deexcitation of the initially stored excitation energy into that of the relative motion for later times. This feedback behaviour of the internal excitation energy which results in particular to the deexcitation of high energetic 1p-1h pairs is probably not realistic due to the coupling of this states to more complex states with high density. It is studied the influence of this coupling due to the residual interaction between the nucleons on the dynamics of two colliding heavy ions

Excited states configurations of the quantum Toda lattice

International Nuclear Information System (INIS)

Matsuyama, A.

2001-01-01

Excited states configurations of the quantum Toda lattice are studied by the direct diagonalization of the Hamiltonian. The most probable configurations of one-hole and one-particle excitations are shown to be similar to the profiles of classical phonon and soliton excitations, respectively. One-hole excitation states, which are always ground states of definite E m -symmetry of the dihedral group D N , change those structures abruptly with the potential range varied. One-particle excitations, which are buried in complicated excitation spectra, have well-defined configurations similar to the conoidal profile of the classical periodic Toda lattice. The relationship that the hole (particle) excitations in quantum mechanics correspond to the phonon (soliton) excitations in classical mechanics, which has been suggested based on the similarity of dispersion relations, is confirmed in a geometrically understandable way. Based on the study of one-soliton and two-soliton states, the structure of multi-soliton states in quantum mechanics can be conjectured

Application of spectroscopy and super-resolution microscopy: Excited state

Energy Technology Data Exchange (ETDEWEB)

Bhattacharjee, Ujjal [Iowa State Univ., Ames, IA (United States)

2016-02-19

Photophysics of inorganic materials and organic molecules in complex systems have been extensively studied with absorption and emission spectroscopy.1-4 Steady-state and time-resolved fluorescence studies are commonly carried out to characterize excited-state properties of fluorophores. Although steady-state fluorescence measurements are widely used for analytical applications, time-resolved fluorescence measurements provide more detailed information about excited-state properties and the environment in the vicinity of the fluorophore. Many photophysical processes, such as photoinduced electron transfer (PET), rotational reorientation, solvent relaxation, and energy transfer, occur on a nanosecond (10^-9 s) timescale, thus affecting the lifetime of the fluorophores. Moreover, time-resolved microscopy methods, such as lifetimeimaging, combine the benefits of the microscopic measurement and information-rich, timeresolved data. Thus, time-resolved fluorescence spectroscopy combined with microscopy can be used to quantify these processes and to obtain a deeper understanding of the chemical surroundings of the fluorophore in a small area under investigation. This thesis discusses various photophysical and super-resolution microscopic studies of organic and inorganic materials, which have been outlined below.

Purity of Gaussian states: Measurement schemes and time evolution in noisy channels

International Nuclear Information System (INIS)

Paris, Matteo G.A.; Illuminati, Fabrizio; Serafini, Alessio; De Siena, Silvio

2003-01-01

We present a systematic study of the purity for Gaussian states of single-mode continuous variable systems. We prove the connection of purity to observable quantities for these states, and show that the joint measurement of two conjugate quadratures is necessary and sufficient to determine the purity at any time. The statistical reliability and the range of applicability of the proposed measurement scheme are tested by means of Monte Carlo simulated experiments. We then consider the dynamics of purity in noisy channels. We derive an evolution equation for the purity of general Gaussian states both in thermal and in squeezed thermal baths. We show that purity is maximized at any given time for an initial coherent state evolving in a thermal bath, or for an initial squeezed state evolving in a squeezed thermal bath whose asymptotic squeezing is orthogonal to that of the input state

Coherence Evolution and Transfer Supplemented by Sender's Initial-State Restoring

Science.gov (United States)

Fel'dman, E. B.; Zenchuk, A. I.

2017-12-01

The evolution of quantum coherences comes with a set of conservation laws provided that the Hamiltonian governing this evolution conserves the spin-excitation number. At that, coherences do not intertwist during the evolution. Using the transmission line and the receiver in the initial ground state we can transfer the coherences to the receiver without interaction between them, although the matrix elements contributing to each particular coherence intertwist in the receiver's state. Therefore we propose a tool based on the unitary transformation at the receiver side to untwist these elements and thus restore (at least partially) the structure of the sender's initial density matrix. A communication line with two-qubit sender and receiver is considered as an example of implementation of this technique.

Excitation of nuclear states by synchrotron radiation

International Nuclear Information System (INIS)

Olariu, Albert

2003-01-01

We study the excitation of nuclear states by gamma ray beams of energy up to 200 keV produced as synchrotron radiation. We consider the possibility to populate an excited state |i> in two steps, from the ground state |g> to an intermediary state |n> which decays by gamma emission or internal conversion to a lower state |i>. The aim of this study is to establish that the probability P 2 of the two-step transition |g> → |n> → |i> should be greater than the probability P 1 of the direct transition |g> → |i>. The probabilities P 1 and P 2 correspond to a radiation pulse of duration equal to the half-time of the state |i>. We have written a computer program in C++ which computes the probability P 2 , the ratio P 2 /P 1 and the rate C 2 of the two-step transitions for any nuclei and different configurations of states. The program uses a database which contains information on the energy levels, half-lives, spins and parities of nuclear states and on the relative intensities of the nuclear transitions. If the half-lives or the relative intensities are not known the program uses the Weisskopf estimates for the transition half-lives. An interpolation program of internal conversion coefficients has also been used. We listed the values obtained for P 2 , P 2 /P 1 and C 2 in a number of cases in which P 2 is significant from the 2900 considered cases. The states |i> and |n> have the energies E i and E n , the corresponding half-lives being t i and t n . The spectral density of the synchrotron radiation has been considered to be 10 12 photons cm -2 s -1 eV -1 . We listed only the cases for which the relative intensities of the transitions from levels |n> and |i> to lower states are known. The calculations carried out in this study allowed us to identify nuclei for which P 2 has relatively great values. In the listed cases P 2 /P 1 >>1, so that the two-step excitation by synchrotron radiation is more efficient than the direct excitation |g> → |i>. For a sample having 10

Efficient determination of the Markovian time-evolution towards a steady-state of a complex open quantum system

Science.gov (United States)

Jonsson, Thorsteinn H.; Manolescu, Andrei; Goan, Hsi-Sheng; Abdullah, Nzar Rauf; Sitek, Anna; Tang, Chi-Shung; Gudmundsson, Vidar

2017-11-01

Master equations are commonly used to describe time evolution of open systems. We introduce a general computationally efficient method for calculating a Markovian solution of the Nakajima-Zwanzig generalized master equation. We do so for a time-dependent transport of interacting electrons through a complex nano scale system in a photon cavity. The central system, described by 120 many-body states in a Fock space, is weakly coupled to the external leads. The efficiency of the approach allows us to place the bias window defined by the external leads high into the many-body spectrum of the cavity photon-dressed states of the central system revealing a cascade of intermediate transitions as the system relaxes to a steady state. The very diverse relaxation times present in the open system, reflecting radiative or non-radiative transitions, require information about the time evolution through many orders of magnitude. In our approach, the generalized master equation is mapped from a many-body Fock space of states to a Liouville space of transitions. We show that this results in a linear equation which is solved exactly through an eigenvalue analysis, which supplies information on the steady state and the time evolution of the system.

Excited-state relaxation of some aminoquinolines

Directory of Open Access Journals (Sweden)

2006-01-01

Full Text Available The absorption and fluorescence spectra, fluorescence quantum yields and lifetimes, and fluorescence rate constants ( k f of 2-amino-3-( 2 ′ -benzoxazolylquinoline (I, 2-amino-3-( 2 ′ -benzothiazolylquinoline (II, 2-amino-3-( 2 ′ -methoxybenzothiazolyl-quinoline (III, 2-amino-3-( 2 ′ -benzothiazolylbenzoquinoline (IV at different temperatures have been measured. The shortwavelength shift of fluorescence spectra of compounds studied (23–49 nm in ethanol as the temperature decreases (the solvent viscosity increases points out that the excited-state relaxation process takes place. The rate of this process depends essentially on the solvent viscosity, but not the solvent polarity. The essential increasing of fluorescence rate constant k f (up to about 7 times as the solvent viscosity increases proves the existence of excited-state structural relaxation consisting in the mutual internal rotation of molecular fragments of aminoquinolines studied, followed by the solvent orientational relaxation.

Electric quadrupole excitation of the first excited state of 11B

International Nuclear Information System (INIS)

Fewell, M.P.; Spear, R.H.; Zabel, T.H.; Baxter, A.M.

1980-02-01

The Coulomb excitation of backscattered 11 B projectiles has been used to measure the reduced E2 transition probability B(E2; 3/2 - →1/2 - ) between the 3/2 - ground state and the 1/2 - first excited state of 11 B. It is found that B(E2; 3/2 - →1/2 - ) = 2.1 +- 0.4 e 2 fm 4 , which agrees with shell-model predictions but is a factor of 10 larger than the prediction of the core-excitation model

Excited-state structure and electronic dephasing time of Nile blue from absolute resonance Raman intensities

Science.gov (United States)

Lawless, Mary K.; Mathies, Richard A.

1992-06-01

Absolute resonance Raman cross sections are measured for Nile blue 690 perchlorate dissolved in ethylene glycol with excitation at 514, 531, and 568 nm. These values and the absorption spectrum are modeled using a time-dependent wave packet formalism. The excited-state equilibrium geometry changes are quantitated for 40 resonance Raman active modes, seven of which (590, 1141, 1351, 1429, 1492, 1544, and 1640 cm-1 ) carry 70% of the total resonance Raman intensity. This demonstrates that in addition to the prominent 590 and 1640 cm-1 modes, a large number of vibrational degrees of freedom are Franck-Condon coupled to the electronic transition. After exposure of the explicit vibrational progressions, the residual absorption linewidth is separated into its homogeneous [350 cm-1 half-width at half-maximum (HWHM)] and inhomogeneous (313 cm-1 HWHM) components through an analysis of the absolute Raman cross sections. The value of the electronic dephasing time derived from this study (25 fs) compares well to previously published results. These data should be valuable in multimode modeling of femtosecond experiments on Nile blue.

A benchmark study of electronic excitation energies, transition moments, and excited-state energy gradients on the nicotine molecule

Energy Technology Data Exchange (ETDEWEB)

Egidi, Franco, E-mail: franco.egidi@sns.it; Segado, Mireia; Barone, Vincenzo, E-mail: vincenzo.barone@sns.it [Scuola Normale Superiore, Piazza dei Cavalieri, 7 I-56126 Pisa (Italy); Koch, Henrik [Department of Chemistry, Norwegian University of Science and Technology, 7491 Trondheim (Norway); Cappelli, Chiara [Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via G. Moruzzi, 3 I-56124 Pisa (Italy)

2014-12-14

In this work, we report a comparative study of computed excitation energies, oscillator strengths, and excited-state energy gradients of (S)-nicotine, chosen as a test case, using multireference methods, coupled cluster singles and doubles, and methods based on time-dependent density functional theory. This system was chosen because its apparent simplicity hides a complex electronic structure, as several different types of valence excitations are possible, including n-π{sup *}, π-π{sup *}, and charge-transfer states, and in order to simulate its spectrum it is necessary to describe all of them consistently well by the chosen method.

Photoionization of furan from the ground and excited electronic states.

Science.gov (United States)

Ponzi, Aurora; Sapunar, Marin; Angeli, Celestino; Cimiraglia, Renzo; Došlić, Nađa; Decleva, Piero

2016-02-28

Here we present a comparative computational study of the photoionization of furan from the ground and the two lowest-lying excited electronic states. The study aims to assess the quality of the computational methods currently employed for treating bound and continuum states in photoionization. For the ionization from the ground electronic state, we show that the Dyson orbital approach combined with an accurate solution of the continuum one particle wave functions in a multicenter B-spline basis, at the density functional theory (DFT) level, provides cross sections and asymmetry parameters in excellent agreement with experimental data. On the contrary, when the Dyson orbitals approach is combined with the Coulomb and orthogonalized Coulomb treatments of the continuum, the results are qualitatively different. In excited electronic states, three electronic structure methods, TDDFT, ADC(2), and CASSCF, have been used for the computation of the Dyson orbitals, while the continuum was treated at the B-spline/DFT level. We show that photoionization observables are sensitive probes of the nature of the excited states as well as of the quality of excited state wave functions. This paves the way for applications in more complex situations such as time resolved photoionization spectroscopy.

Triplet excited electronic state switching induced by hydrogen bonding: A transient absorption spectroscopy and time-dependent DFT study

Energy Technology Data Exchange (ETDEWEB)

Ravi Kumar, Venkatraman; Ariese, Freek; Umapathy, Siva, E-mail: umapathy@ipc.iisc.ernet.in [Inorganic and Physical Chemistry Department, Indian Institute of Science, Bangalore 560012 (India)

2016-03-21

The solvent plays a decisive role in the photochemistry and photophysics of aromatic ketones. Xanthone (XT) is one such aromatic ketone and its triplet-triplet (T-T) absorption spectra show intriguing solvatochromic behavior. Also, the reactivity of XT towards H-atom abstraction shows an unprecedented decrease in protic solvents relative to aprotic solvents. Therefore, a comprehensive solvatochromic analysis of the triplet-triplet absorption spectra of XT was carried out in conjunction with time dependent density functional theory using the ad hoc explicit solvent model approach. A detailed solvatochromic analysis of the T-T absorption bands of XT suggests that the hydrogen bonding interactions are different in the corresponding triplet excited states. Furthermore, the contributions of non-specific and hydrogen bonding interactions towards differential solvation of the triplet states in protic solvents were found to be of equal magnitude. The frontier molecular orbital and electron density difference analysis of the T{sub 1} and T{sub 2} states of XT indicates that the charge redistribution in these states leads to intermolecular hydrogen bond strengthening and weakening, respectively, relative to the S{sub 0} state. This is further supported by the vertical excitation energy calculations of the XT-methanol supra-molecular complex. The intermolecular hydrogen bonding potential energy curves obtained for this complex in the S{sub 0}, T{sub 1}, and T{sub 2} states support the model. In summary, we propose that the different hydrogen bonding mechanisms exhibited by the two lowest triplet excited states of XT result in a decreasing role of the nπ{sup ∗} triplet state, and are thus responsible for its reduced reactivity towards H-atom abstraction in protic solvents.

Stability of quantum-dot excited-state laser emission under simultaneous ground-state perturbation

Energy Technology Data Exchange (ETDEWEB)

Kaptan, Y., E-mail: yuecel.kaptan@physik.tu-berlin.de; Herzog, B.; Schöps, O.; Kolarczik, M.; Woggon, U.; Owschimikow, N. [Institut für Optik und Atomare Physik, Technische Universität Berlin, Berlin (Germany); Röhm, A.; Lingnau, B.; Lüdge, K. [Institut für Theoretische Physik, Technische Universität Berlin, Berlin (Germany); Schmeckebier, H.; Arsenijević, D.; Bimberg, D. [Institut für Festkörperphysik, Technische Universität Berlin, Berlin (Germany); Mikhelashvili, V.; Eisenstein, G. [Technion Institute of Technology, Faculty of Electrical Engineering, Haifa (Israel)

2014-11-10

The impact of ground state amplification on the laser emission of In(Ga)As quantum dot excited state lasers is studied in time-resolved experiments. We find that a depopulation of the quantum dot ground state is followed by a drop in excited state lasing intensity. The magnitude of the drop is strongly dependent on the wavelength of the depletion pulse and the applied injection current. Numerical simulations based on laser rate equations reproduce the experimental results and explain the wavelength dependence by the different dynamics in lasing and non-lasing sub-ensembles within the inhomogeneously broadened quantum dots. At high injection levels, the observed response even upon perturbation of the lasing sub-ensemble is small and followed by a fast recovery, thus supporting the capacity of fast modulation in dual-state devices.

A note on calm excited states of inflation

International Nuclear Information System (INIS)

Ashoorioon, Amjad; Shiu, Gary

2011-01-01

We identify a two-parameter family of excited states within slow-roll inflation for which either the corrections to the two-point function or the characteristic signatures of excited states in the three-point function — i.e. the enhancement for the flattened momenta configurations– are absent. These excited states may nonetheless violate the adiabaticity condition maximally. We dub these initial states of inflation calm excited states. We show that these two sets do not intersect, i.e., those that leave the power-spectrum invariant can be distinguished from their bispectra, and vice versa. The same set of calm excited states that leave the two-point function invariant for slow-roll inflation, do the same task for DBI inflation. However, at the level of three-point function, the calm excited states whose flattened configuration signature is absent for slow-roll inflation, will lead to an enhancement for DBI inflation generally, although the signature is smaller than what suggested by earlier analysis. This example also illustrates that imposing the Wronskian condition is important for obtaining a correct estimate of the non-Gaussian signatures

Competition between excited core states and 1homega single-particle excitations at comparable energies in {sup 207}Pb from photon scattering

Energy Technology Data Exchange (ETDEWEB)

Pietralla, N., E-mail: pietralla@ikp.tu-darmstadt.d [Institut fuer Kernphysik, Technische Universitaet Darmstadt, 64289 Darmstadt (Germany); Nuclear Structure Laboratory, SUNY at Stony Brook, Stony Brook, NY 11794-3800 (United States); Institut fuer Kernphysik, Universitaet zu Koeln, 50937 Koeln (Germany); Li, T.C. [Nuclear Structure Laboratory, SUNY at Stony Brook, Stony Brook, NY 11794-3800 (United States); Fritzsche, M. [Institut fuer Kernphysik, Technische Universitaet Darmstadt, 64289 Darmstadt (Germany); Ahmed, M.W. [Triangle Universities Nuclear Laboratory (TUNL), Duke University, Durham, NC 27708 (United States); Ahn, T.; Costin, A. [Institut fuer Kernphysik, Technische Universitaet Darmstadt, 64289 Darmstadt (Germany); Nuclear Structure Laboratory, SUNY at Stony Brook, Stony Brook, NY 11794-3800 (United States); Institut fuer Kernphysik, Universitaet zu Koeln, 50937 Koeln (Germany); Enders, J. [Institut fuer Kernphysik, Technische Universitaet Darmstadt, 64289 Darmstadt (Germany); Li, J. [Duke Free Electron Laser Laboratory (DFELL), Duke University, Durham, NC 27708 (United States); Mueller, S.; Neumann-Cosel, P. von [Institut fuer Kernphysik, Technische Universitaet Darmstadt, 64289 Darmstadt (Germany); Pinayev, I.V. [Duke Free Electron Laser Laboratory (DFELL), Duke University, Durham, NC 27708 (United States); Ponomarev, V.Yu.; Savran, D. [Institut fuer Kernphysik, Technische Universitaet Darmstadt, 64289 Darmstadt (Germany); Tonchev, A.P.; Tornow, W.; Weller, H.R. [Triangle Universities Nuclear Laboratory (TUNL), Duke University, Durham, NC 27708 (United States); Werner, V. [A.W. Wright Nuclear Structure Laboratory (WNSL), Yale University, New Haven, CT (United States); Wu, Y.K. [Duke Free Electron Laser Laboratory (DFELL), Duke University, Durham, NC 27708 (United States); Zilges, A. [Institut fuer Kernphysik, Universitaet zu Koeln, 50937 Koeln (Germany)

2009-10-26

The Pb(gamma{sup -}>,gamma{sup '}) photon scattering reaction has been studied with the nearly monochromatic, linearly polarized photon beams at the High Intensity gamma-ray Source (HIgammaS) at the DFELL. Azimuthal scattering intensity asymmetries measured with respect to the polarization plane of the beam have been used for the first time to assign both the spin and parity quantum numbers of dipole excited states of {sup 206,207,208}Pb at excitation energies in the vicinity of 5.5 MeV. Evidence for dominant particle-core coupling is deduced from these results along with information on excitation energies and electromagnetic transition matrix elements. Implications of the existence of weakly coupled states built on highly excited core states in competition with 1homega single particle (hole) excitations at comparable energies are discussed.

Process to produce excited states of atomic nuclei

International Nuclear Information System (INIS)

Morita, M.; Morita, R.

The claims of a patented process which relates to the production of excited states of atomic nuclei are outlined. Among these are (1) production of nuclear excited states by bombarding the atoms with x rays or electrons under given conditions, (2) production of radioactive substances by nuclear excitation with x rays or electrons, (3) separation of specific isotopes from a mixture of isotopes of the same element by means of nuclear excitation followed by chemical treatment. The invention allows production of excited states of atomic nuclei in a relatively simple manner without the need of large apparatus and equipment

Time-resolved resonance raman spectrum of all-trans-diphenylbutadiene in the lowest excited singlet state

DEFF Research Database (Denmark)

Wilbrandt, Robert Walter; Jensen, Niels-Henrik; Langkilde, F.W.

1984-01-01

The resonance Raman spectrwn of all-trans-diphenylbutadiene in its lowest excited S1 state excited in resonance with the S1 → Sn absorption band at 650 nm in non-polar solvents is reported. Three vibrational bands at 1572, 1481 and 1165 cm−1 are observed. A possible assignment of the the 1481 cm−...

Excited-State Dynamics of Oxyluciferin in Firefly Luciferase

KAUST Repository

Snellenburg, Joris J.; Laptenok, Sergey P.; DeSa, Richard J.; Naumov, Pance; Solntsev, Kyril M.

2016-01-01

The color variations of light emitted by some natural and mutant luciferases are normally attributed to collective factors referred to as microenvironment effects; however, the exact nature of these interactions between the emitting molecule (oxyluciferin) and the active site remains elusive. Although model studies of noncomplexed oxyluciferin and its variants have greatly advanced the understanding of its photochemistry, extrapolation of the conclusions to the real system requires assumptions about the polarity and proticity of the active site. To decipher the intricate excited-state dynamics, global and target analysis is performed here for the first time on the steady-state and time-resolved spectra of firefly oxyluciferin complexed with luciferase from the Japanese firefly (Luciola cruciata). The experimental steady-state and time resolved luminescence spectra of the oxyluciferin/luciferase complex in solution are compared with the broadband time-resolved firefly bioluminescence recorded in vivo. The results demonstrate that de-excitation of the luminophore results in a complex cascade of photoinduced proton transfer processes and can be interpreted by the pH dependence of the emitted light. It is confirmed that proton transfer is the central event in the spectrochemistry of this system for which any assignment of the pH dependent emission to a single chemical species would be an oversimplification.

Excited-State Dynamics of Oxyluciferin in Firefly Luciferase

KAUST Repository

Snellenburg, Joris J.

2016-11-23

The color variations of light emitted by some natural and mutant luciferases are normally attributed to collective factors referred to as microenvironment effects; however, the exact nature of these interactions between the emitting molecule (oxyluciferin) and the active site remains elusive. Although model studies of noncomplexed oxyluciferin and its variants have greatly advanced the understanding of its photochemistry, extrapolation of the conclusions to the real system requires assumptions about the polarity and proticity of the active site. To decipher the intricate excited-state dynamics, global and target analysis is performed here for the first time on the steady-state and time-resolved spectra of firefly oxyluciferin complexed with luciferase from the Japanese firefly (Luciola cruciata). The experimental steady-state and time resolved luminescence spectra of the oxyluciferin/luciferase complex in solution are compared with the broadband time-resolved firefly bioluminescence recorded in vivo. The results demonstrate that de-excitation of the luminophore results in a complex cascade of photoinduced proton transfer processes and can be interpreted by the pH dependence of the emitted light. It is confirmed that proton transfer is the central event in the spectrochemistry of this system for which any assignment of the pH dependent emission to a single chemical species would be an oversimplification.

Photoionization of excited molecular states using multiphoton excitation techniques

International Nuclear Information System (INIS)

Dehmer, P.M.; Pratt, S.T.; Dehmer, J.L.

1984-01-01

Photoelectron spectra are reported for three photon resonant, four photon ionization of H 2 via the B 1 Σ + /sub u/, v = 7 (J = 2,4) and C 1 Pi/sub u/, v = 0-4 (J = 1) levels and of N 2 via the o 3 1 Pi/sub u/, v = 1,2, b 1 Pi/sub u/, v = 3-5, and c 1 Pi/sub u/, v = 0 levels. The results reflect both the spectroscopy and the dynamics of photoionization of excited molecular states and are discussed in terms of the selection rules for photoionization and the relative probabilities of photoionization from Rydberg and valence states. In some cases, in accordance with the Franck-Condon principle, the results demonstrate that resonant multiphoton ionization through Rydberg states may be a powerful technique for the production of electronic, vibrational, and rotational state selected ions. However, in other cases, systematic departures from Franck-Condon factors are observed, which reflect the more subtle dynamics of excited state photoionization

Excited state nuclear forces from the Tamm-Dancoff approximation to time-dependent density functional theory within the plane wave basis set framework

Science.gov (United States)

Hutter, Jürg

2003-03-01

An efficient formulation of time-dependent linear response density functional theory for the use within the plane wave basis set framework is presented. The method avoids the transformation of the Kohn-Sham matrix into the canonical basis and references virtual orbitals only through a projection operator. Using a Lagrangian formulation nuclear derivatives of excited state energies within the Tamm-Dancoff approximation are derived. The algorithms were implemented into a pseudo potential/plane wave code and applied to the calculation of adiabatic excitation energies, optimized geometries and vibrational frequencies of three low lying states of formaldehyde. An overall good agreement with other time-dependent density functional calculations, multireference configuration interaction calculations and experimental data was found.

The properties of 4'-N,N-dimethylaminoflavonol in the ground and excited states

Science.gov (United States)

Moroz, V. V.; Chalyi, A. G.; Roshal, A. D.

2008-09-01

The mechanism of protonation of 4-N,N-dimethylaminoflavonol and the structure of its protolytic forms in the ground and excited states were studied by electron absorption and fluorescence (steady-state and time-resolved) spectroscopy and with the use of the RM1 quantum-chemical method. A comparison of equilibrium constants and the theoretical enthalpies of formation showed that excitation should be accompanied by the inversion of the basicity of the electron acceptor groups of this compound and, as a consequence, changes in the structure of its monocationic form. An analysis of the spectral parameters of the protolytic 4-N,N-dimethylaminoflavonol forms, however, showed that their structure and the sequence of protonation in the excited state were the same as in the ground state. Changes in the structure of the monocation in the excited state were not observed because of the fast radiationless deactivation of this form and the occurrence of excited state intramolecular proton transfer in aprotic solvents.

Charge transfer excitations from excited state Hartree-Fock subsequent minimization scheme

International Nuclear Information System (INIS)

Theophilou, Iris; Tassi, M.; Thanos, S.

2014-01-01

Photoinduced charge-transfer processes play a key role for novel photovoltaic phenomena and devices. Thus, the development of ab initio methods that allow for an accurate and computationally inexpensive treatment of charge-transfer excitations is a topic that nowadays attracts a lot of scientific attention. In this paper we extend an approach recently introduced for the description of single and double excitations [M. Tassi, I. Theophilou, and S. Thanos, Int. J. Quantum Chem. 113, 690 (2013); M. Tassi, I. Theophilou, and S. Thanos, J. Chem. Phys. 138, 124107 (2013)] to allow for the description of intermolecular charge-transfer excitations. We describe an excitation where an electron is transferred from a donor system to an acceptor one, keeping the excited state orthogonal to the ground state and avoiding variational collapse. These conditions are achieved by decomposing the space spanned by the Hartree-Fock (HF) ground state orbitals into four subspaces: The subspace spanned by the occupied orbitals that are localized in the region of the donor molecule, the corresponding for the acceptor ones and two more subspaces containing the virtual orbitals that are localized in the neighborhood of the donor and the acceptor, respectively. Next, we create a Slater determinant with a hole in the subspace of occupied orbitals of the donor and a particle in the virtual subspace of the acceptor. Subsequently we optimize both the hole and the particle by minimizing the HF energy functional in the corresponding subspaces. Finally, we test our approach by calculating the lowest charge-transfer excitation energies for a set of tetracyanoethylene-hydrocarbon complexes that have been used earlier as a test set for such kind of excitations

Excited State Spectra and Dynamics of Phenyl-Substituted Butadienes

DEFF Research Database (Denmark)

Wallace-Williams, Stacie E.; Schwartz, Benjamin J.; Møller, Søren

1994-01-01

indicate that phenyl torsional motion is not important to the excited-state dynamics and reveal alternative excited-state reaction pathways. The results demonstrate how molecular systems that are structually similar can exhibit different electronic properties and excited-state dynamics....

Multicomponent Time-Dependent Density Functional Theory: Proton and Electron Excitation Energies.

Science.gov (United States)

Yang, Yang; Culpitt, Tanner; Hammes-Schiffer, Sharon

2018-04-05

The quantum mechanical treatment of both electrons and protons in the calculation of excited state properties is critical for describing nonadiabatic processes such as photoinduced proton-coupled electron transfer. Multicomponent density functional theory enables the consistent quantum mechanical treatment of more than one type of particle and has been implemented previously for studying ground state molecular properties within the nuclear-electronic orbital (NEO) framework, where all electrons and specified protons are treated quantum mechanically. To enable the study of excited state molecular properties, herein the linear response multicomponent time-dependent density functional theory (TDDFT) is derived and implemented within the NEO framework. Initial applications to FHF - and HCN illustrate that NEO-TDDFT provides accurate proton and electron excitation energies within a single calculation. As its computational cost is similar to that of conventional electronic TDDFT, the NEO-TDDFT approach is promising for diverse applications, particularly nonadiabatic proton transfer reactions, which may exhibit mixed electron-proton vibronic excitations.

Multimode optical fibers: steady state mode exciter.

Science.gov (United States)

Ikeda, M; Sugimura, A; Ikegami, T

1976-09-01

The steady state mode power distribution of the multimode graded index fiber was measured. A simple and effective steady state mode exciter was fabricated by an etching technique. Its insertion loss was 0.5 dB for an injection laser. Deviation in transmission characteristics of multimode graded index fibers can be avoided by using the steady state mode exciter.

Interplay between singlet and triplet excited states in a conformationally locked donor–acceptor dyad

KAUST Repository

Filatov, Mikhail A.

2015-10-13

The synthesis and photophysical characterization of a palladium(II) porphyrin – anthracene dyad bridged via short and conformationally rigid bicyclo[2.2.2]octadiene spacer were achieved. A spectroscopic investigation of the prepared molecule in solution has been undertaken to study electronic energy transfer in excited singlet and triplet states between the anthracene and porphyrin units. By using steady-state and time-resolved photoluminescence spectroscopy it was shown that excitation of the singlet excited state of the anthracene leads to energy transfer to the lower-lying singlet state of porphyrin. Alternatively, excitation of the porphyrin followed by intersystem crossing to the triplet state leads to very fast energy transfer to the triplet state of anthracene. The rate of this energy transfer has been determined by transient absorption spectroscopy. Comparative studies of the dynamics of triplet excited states of the dyad and reference palladium octaethylporphyrin (PdOEP) have been performed.

Interplay between singlet and triplet excited states in a conformationally locked donor–acceptor dyad

KAUST Repository

Filatov, Mikhail A.; Etzold, Fabian; Gehrig, Dominik; Laquai, Fré dé ric; Busko, Dmitri; Landfester, Katharina; Baluschev, Stanislav

2015-01-01

The synthesis and photophysical characterization of a palladium(II) porphyrin – anthracene dyad bridged via short and conformationally rigid bicyclo[2.2.2]octadiene spacer were achieved. A spectroscopic investigation of the prepared molecule in solution has been undertaken to study electronic energy transfer in excited singlet and triplet states between the anthracene and porphyrin units. By using steady-state and time-resolved photoluminescence spectroscopy it was shown that excitation of the singlet excited state of the anthracene leads to energy transfer to the lower-lying singlet state of porphyrin. Alternatively, excitation of the porphyrin followed by intersystem crossing to the triplet state leads to very fast energy transfer to the triplet state of anthracene. The rate of this energy transfer has been determined by transient absorption spectroscopy. Comparative studies of the dynamics of triplet excited states of the dyad and reference palladium octaethylporphyrin (PdOEP) have been performed.

Obtaining Hartree-Fock and density functional theory doubly excited states with Car-Parrinello density matrix search

Science.gov (United States)

Liang, Wenkel; Isborn, Christine M.; Li, Xiaosong

2009-11-01

The calculation of doubly excited states is one of the major problems plaguing the modern day excited state workhorse methodology of linear response time dependent Hartree-Fock (TDHF) and density function theory (TDDFT). We have previously shown that the use of a resonantly tuned field within real-time TDHF and TDDFT is able to simultaneously excite both the α and β electrons to achieve the two-electron excited states of minimal basis H2 and HeH+ [C. M. Isborn and X. Li, J. Chem. Phys. 129, 204107 (2008)]. We now extend this method to many electron systems with the use of our Car-Parrinello density matrix search (CP-DMS) with a first-principles fictitious mass method for wave function optimization [X. Li, C. L. Moss, W. Liang, and Y. Feng, J. Chem. Phys. 130, 234115 (2009)]. Real-time TDHF/TDDFT is used during the application of the laser field perturbation, driving the electron density toward the doubly excited state. The CP-DMS method then converges the density to the nearest stationary state. We present these stationary state doubly excited state energies and properties at the HF and DFT levels for H2, HeH+, lithium hydride, ethylene, and butadiene.

Black hole state evolution, final state and Hawking radiation

International Nuclear Information System (INIS)

Ahn, D

2012-01-01

The effect of a black hole state evolution on the Hawking radiation is studied using the final state boundary condition. It is found that the thermodynamic or statistical mechanical properties of a black hole depend strongly on the unitary evolution operator S, which determines the black hole state evolution. When the operator S is random unitary or pseudo-random unitary, a black hole emits thermal radiation as predicted by Hawking three decades ago. In particular, when the black hole mass of the final state vanishes, Hawking’s original result is retrieved. On the other hand, it is found that the emission of the Hawking radiation could be suppressed when the evolution of a black hole state is determined by the generator of the coherent state. Such a case can occur for some primordial black holes with Planck scale mass formed by primordial density fluctuations through the process of squeezing the zero-point quantum fluctuation of a scalar field. Those primordial black holes can survive until the present time and can contribute to cold dark matter. (paper)

Generation and Evolution of Chaos in Double-Well Duffing Oscillator under Parametrical Excitation

Directory of Open Access Journals (Sweden)

Ying Zhang

2016-01-01

Full Text Available The generation and evolution of chaotic motion in double-well Duffing oscillator under harmonic parametrical excitation are investigated. Firstly, the complex dynamical behaviors are studied by applying multibifurcation diagram and Poincaré sections. Secondly, by means of Melnikov’s approach, the threshold value of parameter μ for generation of chaotic behavior in Smale horseshoe sense is calculated. By the numerical simulation, it is obvious that as μ exceeds this threshold value, the behavior of Duffing oscillator is still steady-state periodic but the transient motion is chaotic; until the top Lyapunov exponent turns to positive, the motion of system turns to permanent chaos. Therefore, in order to gain an insight into the evolution of chaotic behavior after μ passing the threshold value, the transient motion, basin of attraction, and basin boundary are also investigated.

Photoionization of excited molecular states using multiphoton excitation techniques

International Nuclear Information System (INIS)

Dehmer, P.M.; Pratt, S.T.; Dehmer, J.L.

1984-01-01

Photoelectron spectra are reported for three photon resonant, four photon ionization of H 2 via the B 1 Σ/sub u/ + , v = 7 (J = 2,4) and C 1 π/sub u'/, v = 0-4 (J = 1) levels and of N 2 via the o 3 1 π/sub u'/, v = 1,2, b 1 π/sub u'/, v = 3-5, and c 1 π/sub u'/, v = 0 levels. The results reflect both the spectroscopy and the dynamics of photoionization of excited molecular states and are discussed in terms of the selection rules for photoionization and the relative probabilities of photoionization from Rydberg and valence states. In some cases, in accordance with the Franck-Condon principle, the results demonstrate that resonant multiphoton ionization through Rydberg states may be a powerful technique for the production of electronic, vibrational, and rotational state selected ions. However, in other cases, systematic departures from Franck-Condon factors are observed, which reflect the more subtle dynamics of excited state photoionization. 23 references, 6 figures, 2 tables

Intramolecular evolution from a locally excited state to an excimer-like state in a multichromophoric dendrimer evidenced by a femtosecond fluorescence upconversion study

NARCIS (Netherlands)

Karni, Y.; Jordens, S.; Belder, G. De; Schweitzer, G.; Hofkens, J.; Gensch, T.; Maus, M.; Schryver, F.C. De; Herrmann, A.; Müllen, K.

1999-01-01

A time-resolved fluorescence upconversion study on a polyphenylene dendrimer with eight peryleneimide chromophores on the surface and on a monochromophoric model compound is reported. The time-dependent fluorescence spectra of the dendrimer show that the initial excitation is into a locally excited

Localized excitations and the geometry of the 1nπ* excited states of pyrazine

International Nuclear Information System (INIS)

Kleier, D.A.; Martin, R.L.; Wadt, W.R.; Moomaw, W.R.

1982-01-01

Previous theoretical work has shown that the lowest excited singlet state of pyrazine, the π* 1 B 3 u state, is best described in terms of interacting excitations localized on each nitrogen. The present work refines the localized excitation model and considers its implications for the geometry of the 1 B 3 u state. Hartree-Fock calculations show that the best single configuration description of the nπ* state has broken ( 1 B 1 ) symmetry with the excitation strongly localized at one end of the molcule. If the symmetry-restricted hf result is used for reference, this localization describes an important correlation effect. The excited-state geometry was probed using configuration interaction wave functions based on the symmetry-restricted orbitals, as well as properly symmetrized ''valance-bond'' wave functions based on the broken symmetry solutions. Both descriptions lead to a very flat potential for a b/sub 1u/ vibrational mode. This mode reduces the molecular geometry from D/sub 2h/ to C/sub 2v/. We present spectroscopic evidence of our own and of other workers which is consistent with such a flat potential

Radiative and Excited State Charmonium Physics

Energy Technology Data Exchange (ETDEWEB)

Jozef Dudek

2007-07-30

Renewed interest in the spectroscopy of charmonium has arisen from recent unexpected observations at $e^+e^-$ colliders. Here we report on a series of works from the previous two years examining the radiative physics of charmonium states as well as the mass spectrum of states of higher spin and internal excitation. Using new techniques applied to Domain-Wall and Clover quark actions on quenched isotropic and anisotropic lattices, radiative transitions and two-photon decays are considered for the first time. Comparisons are made with experimental results and with model approaches. Forthcoming application to the light-quark sector of relevance to experiments like Jefferson Lab's GlueX is discussed.

Characterization of excited-state reactions with instant spectra of fluorescence kinetics

International Nuclear Information System (INIS)

Tomin, Vladimir I.; Ushakou, Dzmitryi V.

2015-01-01

Comprehensible knowledge of the excited-state proton transfer processes in organic compounds is overwhelmingly important not only for physics, but also chemistry and Life Sciences, since they play a key role in main processes of photosynthesis and functioning of biological organisms. Moreover compounds with Excited-State Intramolecular Proton Transfer (ESIPT) are in the focus of the interest of scientists throughout the world, because dual fluorescence spectra of such objects corresponding to two forms of molecular structure (normal and photoproduct) are very sensitive to characteristics of molecular microenvironment. This property allows to use such substances as fluorescent probes for diverse applications in chemistry and Life Sciences. But at the same time studying of proton transfer processes is not simple, because this process is characterized by extremely fast times (on picoseconds time scale and less order) and very often contribution of reverse reactions is essentially complicates an interpretation of observed properties of dual fluorescence. Hence, understanding of a role of reversible reactions is crucial for a comprehensive description of all processes accompanying excited state reactions. We discuss new approach for treatment ESIPT reaction on the basis of experimentally measured instant spectra of dual fluorescence and temporal behavior of ratiometric signal of normal to tautomer form intensities. Simple analytical expressions show in transparent way how to distinguish a degree of reverse reaction contribution to ratiometric signal. A validation of the approach under consideration is fulfilled with two different flavonols – 3-hydroxyflavone and 4′-(Dimethylamino)-3-hydroxyflavone – representing two extreme cases in affecting reversible reaction on dual emission. A comparing of new approach and traditional method when we analyze kinetics of separate the N* and T* fluorescence bands decays, has been carried out. - Highlights: • The excited-state

Characterization of excited-state reactions with instant spectra of fluorescence kinetics

Energy Technology Data Exchange (ETDEWEB)

Tomin, Vladimir I., E-mail: tomin@apsl.edu.pl; Ushakou, Dzmitryi V.

2015-10-15

Comprehensible knowledge of the excited-state proton transfer processes in organic compounds is overwhelmingly important not only for physics, but also chemistry and Life Sciences, since they play a key role in main processes of photosynthesis and functioning of biological organisms. Moreover compounds with Excited-State Intramolecular Proton Transfer (ESIPT) are in the focus of the interest of scientists throughout the world, because dual fluorescence spectra of such objects corresponding to two forms of molecular structure (normal and photoproduct) are very sensitive to characteristics of molecular microenvironment. This property allows to use such substances as fluorescent probes for diverse applications in chemistry and Life Sciences. But at the same time studying of proton transfer processes is not simple, because this process is characterized by extremely fast times (on picoseconds time scale and less order) and very often contribution of reverse reactions is essentially complicates an interpretation of observed properties of dual fluorescence. Hence, understanding of a role of reversible reactions is crucial for a comprehensive description of all processes accompanying excited state reactions. We discuss new approach for treatment ESIPT reaction on the basis of experimentally measured instant spectra of dual fluorescence and temporal behavior of ratiometric signal of normal to tautomer form intensities. Simple analytical expressions show in transparent way how to distinguish a degree of reverse reaction contribution to ratiometric signal. A validation of the approach under consideration is fulfilled with two different flavonols – 3-hydroxyflavone and 4′-(Dimethylamino)-3-hydroxyflavone – representing two extreme cases in affecting reversible reaction on dual emission. A comparing of new approach and traditional method when we analyze kinetics of separate the N* and T* fluorescence bands decays, has been carried out. - Highlights: • The excited-state

Observation of excited state charge transfer with fs/ps-CARS

International Nuclear Information System (INIS)

Blom, Alex Jason

2009-01-01

Excited state charge transfer processes are studied using the fs/ps-CARS probe technique. This probe allows for multiplexed detection of Raman active vibrational modes. Systems studied include Michler's Ketone, Coumarin 120, 4-dimethylamino-4(prime)-nitrostilbene, and several others. The vibrational spectrum of the para di-substituted benzophenone Michler's Ketone in the first excited singlet state is studied for the first time. It is found that there are several vibrational modes indicative of structural changes of the excited molecule. A combined experimental and theoretical approach is used to study the simplest 7-amino-4-methylcoumarin, Coumarin 120. Vibrations observed in FTIR and spontaneous Raman spectra are assigned using density functional calculations and a continuum solvation model is used to predict how observed modes are affected upon inclusion of a solvent. The low frequency modes of the excited state charge transfer species 4-dimethylamino-4(prime)-nitrostilbene are studied in acetonitrile. Results are compared to previous work on this molecule in the fingerprint region. Finally, several partially completed projects and their implications are discussed. These include the two photon absorption of Coumarin 120, nanoconfinement in cyclodextrin cavities and sensitization of titania nanoparticles

Observation of excited state charge transfer with fs/ps-CARS

Energy Technology Data Exchange (ETDEWEB)

Blom, Alex Jason [Iowa State Univ., Ames, IA (United States)

2009-01-01

Excited state charge transfer processes are studied using the fs/ps-CARS probe technique. This probe allows for multiplexed detection of Raman active vibrational modes. Systems studied include Michler's Ketone, Coumarin 120, 4-dimethylamino-4'-nitrostilbene, and several others. The vibrational spectrum of the para di-substituted benzophenone Michler's Ketone in the first excited singlet state is studied for the first time. It is found that there are several vibrational modes indicative of structural changes of the excited molecule. A combined experimental and theoretical approach is used to study the simplest 7-amino-4-methylcoumarin, Coumarin 120. Vibrations observed in FTIR and spontaneous Raman spectra are assigned using density functional calculations and a continuum solvation model is used to predict how observed modes are affected upon inclusion of a solvent. The low frequency modes of the excited state charge transfer species 4-dimethylamino-4{prime}-nitrostilbene are studied in acetonitrile. Results are compared to previous work on this molecule in the fingerprint region. Finally, several partially completed projects and their implications are discussed. These include the two photon absorption of Coumarin 120, nanoconfinement in cyclodextrin cavities and sensitization of titania nanoparticles.

Electronic excited states and relaxation dynamics in polymer heterojunction systems

Science.gov (United States)

Ramon, John Glenn Santos

, we examine the effect of the nanoscale interfacial morphology and solvation on the electronic excited states of TFB/F8BT. Here, we employ time-dependent density functional theory (TD-DFT) to investigate the relevant excited states of two stacking configurations. We show that the calculated states agree with the excited states responsible for the experimentally observed emission peaks and that these states are blue shifted relative to those of the isolated chain. Furthermore, slight lateral shifts in the stacking orientation not only shift the excited state energies; more importantly, they alter the nature of these states altogether. Lastly, we see that solvation greatly stabilizes the charge-transfer states.

The triplet excited state of Bodipy: formation, modulation and application.

Science.gov (United States)

Zhao, Jianzhang; Xu, Kejing; Yang, Wenbo; Wang, Zhijia; Zhong, Fangfang

2015-12-21

Boron dipyrromethene (Bodipy) is one of the most extensively investigated organic chromophores. Most of the investigations are focused on the singlet excited state of Bodipy, such as fluorescence. In stark contrast, the study of the triplet excited state of Bodipy is limited, but it is an emerging area, since the triplet state of Bodipy is tremendously important for several areas, such as the fundamental photochemistry study, photodynamic therapy (PDT), photocatalysis and triplet-triplet annihilation (TTA) upconversion. The recent developments in the study of the production, modulation and application of the triplet excited state of Bodipy are discussed in this review article. The formation of the triplet state of Bodipy upon photoexcitation, via the well known approach such as the heavy atom effect (including I, Br, Ru, Ir, etc.), and the new methods, such as using a spin converter (e.g. C60), charge recombination, exciton coupling and the doubly substituted excited state, are summarized. All the Bodipy-based triplet photosensitizers show strong absorption of visible or near IR light and the long-lived triplet excited state, which are important for the application of the triplet excited state in PDT or photocatalysis. Moreover, the methods for switching (or modulation) of the triplet excited state of Bodipy were discussed, such as those based on the photo-induced electron transfer (PET), by controlling the competing Förster-resonance-energy-transfer (FRET), or the intermolecular charge transfer (ICT). Controlling the triplet excited state will give functional molecules such as activatable PDT reagents or molecular devices. It is worth noting that switching of the singlet excited state and the triplet state of Bodipy may follow different principles. Application of the triplet excited state of Bodipy in PDT, hydrogen (H2) production, photoredox catalytic organic reactions and TTA upconversion were discussed. The challenges and the opportunities in these areas were

Vibronic coupling in the excited-states of carotenoids

Energy Technology Data Exchange (ETDEWEB)

Miki, Takeshi [Physikalisch-Chemisches Institut; Ruprecht-Karls-Universität Heidelberg; D-69120 Heidelberg; Germany; Buckup, Tiago [Physikalisch-Chemisches Institut; Ruprecht-Karls-Universität Heidelberg; D-69120 Heidelberg; Germany; Krause, Marie S. [Physikalisch-Chemisches Institut; Ruprecht-Karls-Universität Heidelberg; D-69120 Heidelberg; Germany; Southall, June [College of Medical; Veterinary, and Life Science; University of Glasgow; G12 8QQ Glasgow; UK; Cogdell, Richard J. [College of Medical; Veterinary, and Life Science; University of Glasgow; G12 8QQ Glasgow; UK; Motzkus, Marcus [Physikalisch-Chemisches Institut; Ruprecht-Karls-Universität Heidelberg; D-69120 Heidelberg; Germany

2016-01-01

The ultrafast femtochemistry of carotenoids is governed by the interaction between electronic excited states, which has been explained by the relaxation dynamics within a few hundred femtoseconds from the lowest optically allowed excited state S₂to the optically dark state S₁.

Real time evolution at finite temperatures with operator space matrix product states

International Nuclear Information System (INIS)

Pižorn, Iztok; Troyer, Matthias; Eisler, Viktor; Andergassen, Sabine

2014-01-01

We propose a method to simulate the real time evolution of one-dimensional quantum many-body systems at finite temperature by expressing both the density matrices and the observables as matrix product states. This allows the calculation of expectation values and correlation functions as scalar products in operator space. The simulations of density matrices in inverse temperature and the local operators in the Heisenberg picture are independent and result in a grid of expectation values for all intermediate temperatures and times. Simulations can be performed using real arithmetics with only polynomial growth of computational resources in inverse temperature and time for integrable systems. The method is illustrated for the XXZ model and the single impurity Anderson model. (paper)

Real time evolution at finite temperatures with operator space matrix product states

Science.gov (United States)

Pižorn, Iztok; Eisler, Viktor; Andergassen, Sabine; Troyer, Matthias

2014-07-01

We propose a method to simulate the real time evolution of one-dimensional quantum many-body systems at finite temperature by expressing both the density matrices and the observables as matrix product states. This allows the calculation of expectation values and correlation functions as scalar products in operator space. The simulations of density matrices in inverse temperature and the local operators in the Heisenberg picture are independent and result in a grid of expectation values for all intermediate temperatures and times. Simulations can be performed using real arithmetics with only polynomial growth of computational resources in inverse temperature and time for integrable systems. The method is illustrated for the XXZ model and the single impurity Anderson model.

Rearrangements in ground and excited states

CERN Document Server

de Mayo, Paul

1980-01-01

Rearrangements in Ground and Excited States, Volume 3 presents essays on the chemical generation of excited states; the cis-trans isomerization of olefins; and the photochemical rearrangements in trienes. The book also includes essays on the zimmerman rearrangements; the photochemical rearrangements of enones; the photochemical rearrangements of conjugated cyclic dienones; and the rearrangements of the benzene ring. Essays on the photo rearrangements via biradicals of simple carbonyl compounds; the photochemical rearrangements involving three-membered rings or five-membered ring heterocycles;

Excitation of lowest electronic states of thymine by slow electrons

Science.gov (United States)

Chernyshova, I. V.; Kontros, E. J.; Markush, P. P.; Shpenik, O. B.

2013-11-01

Excitation of lowest electronic states of the thymine molecules in the gas phase is studied by elec- tron energy loss spectroscopy. In addition to dipole-allowed transitions to singlet states, transitions to the lowest triplet states were observed. The low-energy features of the spectrum at 3.66 and 4.61 eV are identified with the excitation of the first triplet states 13 A' (π → π*) and 13 A″ ( n → π*). The higher-lying features at 4.96, 5.75, 6.17, and 7.35 eV are assigned mainly to the excitation of the π → π* transitions to the singlet states of the molecule. The excitation dynamics of the lowest states is studied. It is found that the first triplet state 13 A'(π → π*) is most efficiently excited at a residual energy close to zero, while the singlet 21 A'(π → π*) state is excited with almost identical efficiency at different residual energies.

Electron-impact excitation and ionization cross sections for ground state and excited helium atoms

International Nuclear Information System (INIS)

Ralchenko, Yu.; Janev, R.K.; Kato, T.; Fursa, D.V.; Bray, I.; Heer, F.J. de

2008-01-01

Comprehensive and critically assessed cross sections for the electron-impact excitation and ionization of ground state and excited helium atoms are presented. All states (atomic terms) with n≤4 are treated individually, while the states with n≥5 are considered degenerate. For the processes involving transitions to and from n≥5 levels, suitable cross section scaling relations are presented. For a large number of transitions, from both ground and excited states, convergent close coupling calculations were performed to achieve a high accuracy of the data. The evaluated/recommended cross section data are presented by analytic fit functions, which preserve the correct asymptotic behavior of the cross sections. The cross sections are also displayed in graphical form

Excited-state dynamics of mononucleotides and DNA strands in a deep eutectic solvent.

Science.gov (United States)

Zhang, Yuyuan; de La Harpe, Kimberly; Hariharan, Mahesh; Kohler, Bern

2018-04-17

The photophysics of several mono- and oligonucleotides were investigated in a deep eutectic solvent for the first time. The solvent glyceline, prepared as a 1 : 2 mole ratio mixture of choline chloride and glycerol, was used to study excited-state deactivation in a non-aqueous solvent by the use of steady-state and time-resolved spectroscopy. DNA strands in glyceline retain the secondary structures that are present in aqueous solution to some degree, thus enabling a study of the effects of solvent properties on the excited states of stacked bases and stacked base pairs. The excited-state lifetime of the mononucleotide 5'-AMP in glyceline is 630 fs, or twice as long as in aqueous solution. Even slower relaxation is seen for 5'-TMP in glyceline, and a possible triplet state with a lifetime greater than 3 ns is observed. Circular dichroism spectra show that the single strand (dA)18 and the duplex d(AT)9·d(AT)9 adopt similar structures in glyceline and in aqueous solution. Despite having similar conformations in both solvents, femtosecond transient absorption experiments reveal striking changes in the dynamics. Excited-state decay and vibrational cooling generally take place more slowly in glyceline than in water. Additionally, the fraction of long-lived excited states in both oligonucleotide systems is lower in glyceline than in aqueous solution. For a DNA duplex, water is suggested to favor decay pathways involving intrastrand charge separation, while the deep eutectic solvent favors interstrand deactivation channels involving neutral species. Slower solvation dynamics in the viscous deep eutectic solvent may also play a role. These results demonstrate that the dynamics of excitations in stacked bases and stacked base pairs depend not only on conformation, but are also highly sensitive to the solvent.

Time evolution of the coarse-graining-smoothed Wigner operator in an amplitude dissipative channel: from a pure state to a mixed state

International Nuclear Information System (INIS)

He, Rui; Fan, Hong-yi

2014-01-01

Based on the solution to the master equation of the density operator describing the amplitude dissipative channel, we derive the time evolution law of the coarse-graining-smoothed Wigner operator in this channel, which demonstrates how an initial pure state evolves into a mixed state, exhibiting decoherence

Study of a Quantum Dot in an Excited State

Science.gov (United States)

Slamet, Marlina; Sahni, Viraht

We have studied the first excited singlet state of a quantum dot via quantal density functional theory (QDFT). The quantum dot is represented by a 2D Hooke's atom in an external magnetostatic field. The QDFT mapping is from an excited singlet state of this interacting system to one of noninteracting fermions in a singlet ground state. The results of the study will be compared to (a) the corresponding mapping from a ground state of the quantum dot and (b) to the similar mapping from an excited singlet state of the 3D Hooke's atom.

Thermal effects on the stability of excited atoms in cavities

International Nuclear Information System (INIS)

Khanna, F. C.; Malbouisson, A. P. C.; Malbouisson, J. M. C.; Santana, A. E.

2010-01-01

An atom, coupled linearly to an environment, is considered in a harmonic approximation in thermal equilibrium inside a cavity. The environment is modeled by an infinite set of harmonic oscillators. We employ the notion of dressed states to investigate the time evolution of the atom initially in the first excited level. In a very large cavity (free space) for a long elapsed time, the atom decays and the value of its occupation number is the physically expected one at a given temperature. For a small cavity the excited atom never completely decays and the stability rate depends on temperature.

Bottom-up excited state dynamics of two cinnamate-based sunscreen filter molecules.

Science.gov (United States)

Peperstraete, Yoann; Staniforth, Michael; Baker, Lewis A; Rodrigues, Natércia D N; Cole-Filipiak, Neil C; Quan, Wen-Dong; Stavros, Vasilios G

2016-10-12

Methyl-E-4-methoxycinnamate (E-MMC) is a model chromophore of the commonly used commercial sunscreen agent, 2-ethylhexyl-E-4-methoxycinnamate (E-EHMC). In an effort to garner a molecular-level understanding of the photoprotection mechanisms in operation with E-EHMC, we have used time-resolved pump-probe spectroscopy to explore E-MMC's and E-EHMC's excited state dynamics upon UV-B photoexcitation to the S 1 (1 1 ππ*) state in both the gas- and solution-phase. In the gas-phase, our studies suggest that the excited state dynamics are driven by non-radiative decay from the 1 1 ππ* to the S 3 (1 1 nπ*) state, followed by de-excitation from the 1 1 nπ* to the ground electronic state (S 0 ). Using both a non-polar-aprotic solvent, cyclohexane, and a polar-protic solvent, methanol, we investigated E-MMC and E-EHMC's photochemistry in a more realistic, 'closer-to-shelf' environment. A stark change to the excited state dynamics in the gas-phase is observed in the solution-phase suggesting that the dynamics are now driven by efficient E/Z isomerisation from the initially photoexcited 1 1 ππ* state to S 0 .

Time-evolution of entanglement and Greenberger-Horne-Zeilinger states in two-mode Bose-Einstein condensates

International Nuclear Information System (INIS)

Yin Wen; Zhang, G.-F.; Liang, J.-Q.; Yan, Q.-W.

2004-01-01

In this Brief Report we investigate the time evolution of entanglement in two-mode Bose-Einstein condensates (BEC's) with various parameters of the scattering lengths of interatoms collisions, Josephson coupling strength, and initial states. The degree of entanglement increases by strengthening the tunnel coupling and keeping the balance of the collision interaction. In the latter stage we show that the two-mode BEC's can be used for preparing the Greenberger-Home-Zeilinger state

Lifetime measurements of the excited states in {sup 145} Sm

Energy Technology Data Exchange (ETDEWEB)

El-Badry, A M; Abdel Samie, Sh; Ahmad, A A [Depatment of Physics, Faculty of Science, ElMinia University, ElMinia, (Egypt); Kuroyanagi, T; Odahara, A; Gono, Y; Morinobu, S [Tandem Accelerator Laboratory, Department of Physics, Kyushu University, (Japan)

1997-12-31

Lifetime of the excited levels in {sup 145} Sm has been measured through the {sup 139} La ({sup 10} B, 4 n){sup 145} Sm nuclear reaction. The optimal beam energy of 49 MeV was determined from the measurements of the excitation function and Cascade program. With the possibility of studying lifetime of this nucleus a conventional plunger system have been designed and constructed at kyushu University tandem accelerator laboratory. A La target of 0.22 mg/cm{sup 2} thickness which was evaporated onto a Au foil of 2 mg/cm{sup 2} thickness was used. Since the recoil velocity was estimated to be 1.76 mm/ns (beta 0.00585), the measurable time range resulted in the range from 5 Ps to 5 ns. The single spectra measurements were performed at the 20 plunger positions in the range from 10 {mu} to 10 mm. Analyses of the data were carried using hypermet and/or GF2 program to obtain the lifetimes. A new list of lifetimes for 12 excited states up to 3.922 MeV excitations for {sup 145} Sm were determined for the first time. Decay curves of the these transitions are discussed. The new lifetimes of excited states in {sup 145} Sm enabled us to understand the electromagnetic properties. The deduced transition probabilities were established and compared with that of N = 83 isotones and the closed shell nucleus {sup 144} Sm. In addition, a nuclear structure of {sup 145} Sm have been discussed and proposed in framework of the shell model. 4 figs., 1 tab.

Excited-state dynamics of the medicinal pigment curcumin in a hydrogel.

Science.gov (United States)

Harada, Takaaki; Lincoln, Stephen F; Kee, Tak W

2016-10-12

Curcumin is a yellow polyphenol with multiple medicinal effects. These effects, however, are limited due to its poor aqueous stability and solubility. A hydrogel of 3% octadecyl randomly substituted polyacrylate (PAAC18) has been shown to provide high aqueous stability for curcumin under physiological conditions, offering a route for photodynamic therapy. In this study, the excited-state photophysics of curcumin in the PAAC18 hydrogel is investigated using a combination of femtosecond transient absorption and fluorescence upconversion spectroscopy. The transient absorption results reveal a multiexponential decay in the excited-state kinetics with fast (1 ps & 15 ps) and slow (110 ps & ≈5 ns) components. The fast decay component exhibits a deuterium isotope effect with D 2 O in the hydrogel, indicating that the 15 ps decay component is attributable to excited-state intramolecular hydrogen atom transfer of curcumin in the PAAC18 hydrogel. In addition, solvent reorganisation of excited-state curcumin is investigated using multiwavelength femtosecond fluorescence upconversion spectroscopy. The results show that the dominant solvation response (τ = 0.08 ps) is a fast inertial motion owing to the presence of bulk-like water in the vicinity of the hydrophobic octadecyl substituents of the PAAC18 hydrogel. The results also show an additional response with longer time constants of 1 and 6 ps, which is attributable to translational diffusion of confined water molecules in the three-dimensional, cross-linking network of the octadecyl substituents of PAAC18. Overall, we show that excited-state intramolecular hydrogen atom transfer and solvent reorganisation are major photophysical events for curcumin in the PAAC18 hydrogel.

Lifetime measurements of excited states in 196Pt

International Nuclear Information System (INIS)

Bolotin, H.H.; Katayama, Ichiro; Sakai, Hideyuki; Fujita, Yoshitaka; Fujiwara, Mamoru

1979-01-01

The lifetimes of six excited states in 196 Pt up to an excitation energy of 1525 keV were measured by the recoil-distance method (RDM). These levels were populated by Coulomb excitation using both 90 MeV 20 Ne and 220 MeV 58 Ni ion beams. The measured lifetimes of the 2 1 + , 4 1 + , 6 1 + , 2 2 + , 4 2 + and 0 2 + states and the B(E2) values inferred for the depopulating transitions from these levels are presented. With the exception of the 2 1 + state, the meanlives of all other levels are the first such direct experimental determinations to be reported. (author)

Lifetime measurements of excited states in 73As

International Nuclear Information System (INIS)

Singh, K.P.; Kavakand, T.; Hajivaliei, M.

2004-01-01

The excited states of 73 As have been investigated via the 73 Ge(p, nγ) 73 As reaction with proton beam energies from 2.5–4.3 MeV. The lifetimes of the levels at 769.6, 860.5, 1177.8, 1188.7, 1274.9, 1344.1, 1557.1 and 1975.2 keV excitation energies have been measured for the first time using the Doppler shift attenuation method. The angular distributions have been used to assign the spins and the multipole mixing ratios using statistical theory for compound nuclear reactions. The ambiguity in the spin values for the various levels has been removed. The multipole mixing ratios for eight γ-transitions have been newly measured. (author)

Substituent effects on the excited states of phenyl-capped phenylene vinylene tetramers

NARCIS (Netherlands)

Candeias, L.P.; Gelinck, G.H.; Piet, J.J.; Piris, J.; Wegewijs, B.; Peeters, E.; Wildeman, J.; Hadziioannou, G.; Müllen, K.

2001-01-01

The singlet and triplet excited states of phenyl-capped tetramers of phenylene vinylene with different alkyl, alkoxy or cyano substituents, were investigated in benzene solution. The lowest singlet states were studied by laser flash-photolysis with time-resolved microwave conductivity and

Computing correct truncated excited state wavefunctions

Science.gov (United States)

Bacalis, N. C.; Xiong, Z.; Zang, J.; Karaoulanis, D.

2016-12-01

We demonstrate that, if a wave function's truncated expansion is small, then the standard excited states computational method, of optimizing one "root" of a secular equation, may lead to an incorrect wave function - despite the correct energy according to the theorem of Hylleraas, Undheim and McDonald - whereas our proposed method [J. Comput. Meth. Sci. Eng. 8, 277 (2008)] (independent of orthogonality to lower lying approximants) leads to correct reliable small truncated wave functions. The demonstration is done in He excited states, using truncated series expansions in Hylleraas coordinates, as well as standard configuration-interaction truncated expansions.

Probability of collective excited state decay

International Nuclear Information System (INIS)

Manykin, Eh.A.; Ozhovan, M.I.; Poluehktov, P.P.

1987-01-01

Decay mechanisms of condensed excited state formed of highly excited (Rydberg) atoms are considered, i.e. stability of so-called Rydberg substance is analyzed. It is shown that Auger recombination and radiation transitions are the basic processes. The corresponding probabilities are calculated and compared. It is ascertained that the ''Rydberg substance'' possesses macroscopic lifetime (several seconds) and in a sense it is metastable

Bond Shortening (1.4 Å) in the Singlet and Triplet Excited States of [Ir2(dimen)4]2+ in Solution Determined by Time-Resolved X-ray Scattering

DEFF Research Database (Denmark)

Haldrup, Martin Kristoffer; Harlang, Tobias; Christensen, Morten

2011-01-01

Ground- and excited-state structures of the bimetallic, ligand-bridged compound Ir2(dimen)42+ are investigated in acetonitrile by means of time-resolved X-ray scattering. Following excitation by 2 ps laser pulses at 390 nm, analysis of difference scattering patterns obtained at eight different ti...

Excited-state dynamics of pentacene derivatives with stable radical substituents.

Science.gov (United States)

Ito, Akitaka; Shimizu, Akihiro; Kishida, Noriaki; Kawanaka, Yusuke; Kosumi, Daisuke; Hashimoto, Hideki; Teki, Yoshio

2014-06-23

The excited-state dynamics of pentacene derivatives with stable radical substituents were evaluated in detail through transient absorption measurements. The derivatives showed ultrafast formation of triplet excited state(s) in the pentacene moiety from a photoexcited singlet state through the contributions of enhanced intersystem crossing and singlet fission. Detailed kinetic analyses for the transient absorption data were conducted to quantify the excited-state characteristics of the derivatives. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Time evolution of distribution functions in dissipative environments

International Nuclear Information System (INIS)

Hu Li-Yun; Chen Fei; Wang Zi-Sheng; Fan Hong-Yi

2011-01-01

By introducing the thermal entangled state representation, we investigate the time evolution of distribution functions in the dissipative channels by bridging the relation between the initial distribution function and the any time distribution function. We find that most of them are expressed as such integrations over the Laguerre—Gaussian function. Furthermore, as applications, we derive the time evolution of photon-counting distribution by bridging the relation between the initial distribution function and the any time photon-counting distribution, and the time evolution of R-function characteristic of nonclassicality depth. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

Steady state and time-resolved spectroscopic investigations on the photoreactions involved within the electronically excited electron acceptor 9-cyanoanthracene in presence of benzotriazole and benzimidazole donors

International Nuclear Information System (INIS)

Bhattacharya, Sudeshna; Bardhan, Munmun; Ganguly, Tapan

2010-01-01

The electrochemical, 'steady-state' and 'time-resolved' spectroscopic investigations were made on the well-known electron acceptor 9-cyanoanthracene (CNA) when interacted with the electron donors benzotriazole (BZT) and benzimidazole (BMI) molecules. Though electrochemical measurements indicate the thermodynamical possibility of occurrences of photoinduced electron transfer reactions within these reacting systems in the lowest excited singlet state (S 1 ) of the acceptor CNA but the steady-state and time-resolved measurements clearly demonstrate only the triplet-initiated charge separation reactions. It was reported earlier that in the cases of disubstituted indole molecules the occurrences of photoinduced electron transfer reactions were apparent both in the excited singlet and triplet states of the acceptor 9-cyanoanthracene, but the similarly structured present donor molecules benzotriazole (and benzimidazole) behave differently from indoles. The weak ground state complex formations within the presently studied reacting systems appear to be responsible for the observed static quenching phenomena as evidenced from the time-resolved fluorescence studies. Time-resolved spectroscopic investigations demonstrate the formation of the ground state of the reacting components (donor and acceptor) through recombination of triplet ion-pairs via formations of contact neutral radical produced by H-abstraction mechanism.

Excited-State Dynamics of Melamine and Its Lysine Derivative Investigated by Femtosecond Transient Absorption Spectroscopy

Directory of Open Access Journals (Sweden)

Yuyuan Zhang

2016-11-01

Full Text Available Melamine may have been an important prebiotic information carrier, but its excited-state dynamics, which determine its stability under UV radiation, have never been characterized. The ability of melamine to withstand the strong UV radiation present on the surface of the early Earth is likely to have affected its abundance in the primordial soup. Here, we studied the excited-state dynamics of melamine (a proto-nucleobase and its lysine derivative (a proto-nucleoside using the transient absorption technique with a UV pump, and UV and infrared probe pulses. For melamine, the excited-state population decays by internal conversion with a lifetime of 13 ps without coupling significantly to any photochemical channels. The excited-state lifetime of the lysine derivative is slightly longer (18 ps, but the dominant deactivation pathway is otherwise the same as for melamine. In both cases, the vast majority of excited molecules return to the electronic ground state on the aforementioned time scales, but a minor population is trapped in a long-lived triplet state.

Charge-Transfer Dynamics in the Lowest Excited State of a Pentacene–Fullerene Complex: Implications for Organic Solar Cells

KAUST Repository

Joseph, Saju

2017-10-02

We characterize the dynamic nature of the lowest excited state in a pentacene/C60 complex on the femtosecond time scale, via a combination of ab initio molecular dynamics and time-dependent density functional theory. We analyze the correlations between the molecular vibrations of the complex and the oscillations in the electron-transfer character of its lowest excited state, which point to vibration-induced coherences between the (pentacene-based) local-excitation (LE) state and the complex charge-transfer (CT) state. We discuss the implications of our results on this model system for the exciton-dissociation process in organic solar cells.

Dynamics of excited-state intramolecular proton transfer reactions in piroxicam. Role of triplet states

Science.gov (United States)

Cho, Dae Won; Kim, Yong Hee; Yoon, Minjoong; Jeoung, Sae Chae; Kim, Dongho

1994-08-01

The picosecond time-resolved fluorescence and transient absorption behavior of piroxicam at room temperature are reported. The keto tautomer in the excited singlet state ( 1K*) formed via the fast intramolecular proton transfer (≈ 20 ps) is observed. The short-lived (7.5 ns) triplet state of keto tauomer ( 3K*) is generated from 1K * in toluene whereas it is hardly observed in ethanol. Consequently, rapid reverse proton transfer takes place from 3K * to the enol triplet state ( 3E *.

Time evolution of tokamak states with flow

International Nuclear Information System (INIS)

Kerner, W.; Weitzner, H.

1985-12-01

The general dissipative Braginskii single-fluid model is applied to simulate tokamak transport. An expansion with respect to epsilon = (ω/sub i/tau/sub i/) -1 , the factor by which perpendicular and parallel transport coefficients differ, yields a numerically tractable scheme. The resulting 1-1/2 D procedure requires computation of 2D toroidal equilibria with flow together with the solution of a system of ordinary 1D flux-averaged equations for the time evolution of the profiles. 13 refs

The formation and decay of triply excited He- states in e-He scattering

International Nuclear Information System (INIS)

Heideman, H.G.M.

1988-01-01

A description is given of doubly and triply excited negative-ion states and their effects on the electron impact excitation of atomic states. Mechanisms for indirect excitation of singly excited states are discussed with respect to:- negative-ion resonance, autoionisation and post-collision interaction, and excitation of an autoionising state via a negative ion resonance. A classification of doubly excited states is considered. Experimental results on the excitation of the n'S states of helium as a function of the incident electron energy are presented, along with theoretical PCI (post collision interaction) profiles in excitation functions, and an interpretation of the results. (UK)

Dynamic study of excited state hydrogen-bonded complexes of harmane in cyclohexane-toluene mixtures.

Science.gov (United States)

Carmona, Carmen; Balón, Manuel; Galán, Manuel; Guardado, Pilar; Muñoz, María A

2002-09-01

Photoinduced proton transfer reactions of harmane or 1-methyl-9H-pyrido[3,4-b]indole (HN) in the presence of the proton donor hexafluoroisopropanol (HFIP) in cyclohexane-toluene mixtures (CY-TL; 10% vol/vol of TL) have been studied. Three excited state species have been identified: a 1:2 hydrogen-bonded proton transfer complex (PTC), between the pyridinic nitrogen of the substrate and the proton donor, a hydrogen-bonded cation-like exciplex (CL*) with a stoichiometry of at least 1:3 and a zwitterionic exciplex (Z*). Time-resolved fluorescence measurements evidence that upon excitation of ground state PTC, an excited state equilibrium is established between PTC* and the cationlike exciplex, CL*, lambdaem approximately/= 390 nm. This excited state reaction is assisted by another proton donor molecule. Further reaction of CL* with an additional HFIP molecule produces the zwitterionic species, Z*, lambda(em) approximately/= 500 nm. From the analysis of the multiexponential decays, measured at different emission wavelengths and as a function of HFIP concentration, the mechanism of these excited state reactions has been established. Thus, three rate constants and three reciprocal lifetimes have been determined. The simultaneous study of 1,9-dimethyl-9H-pyrido[3,4-b]indole (MHN) under the same experimental conditions has helped to understand the excited state kinetics of these processes.

Excitation and decay of correlated atomic states

International Nuclear Information System (INIS)

Rau, A.R.P.

1992-01-01

Doubly excited states of atoms and ions in which two electrons are excited from the ground configuration display strong radial and angular electron correlations. They are prototypical examples of quantum-mechanical systems with strong coupling. Two distinguishing characteristics of these states are: (1) their organization into successive families, with only weak coupling between families, and (2) a hierarchical nature of this coupling, with states from one family decaying primarily to those in the next lower family. A view of the pair of electrons as a single entity, with the electron-electron repulsion between them divided into a adiabatic and nonadiabatic piece, accounts for many of the dominant features. The stronger, adiabatic part determines the family structure and the weaker, nonadiabatic part the excitation and decay between successive families. Similar considerations extend to three-electron atomic states, which group into five different classes. They are suggestive of composite models for quarks in elementary particle physics, which exhibit analogous groupings into families with a hierarchical arrangement of masses and electroweak decays. 49 refs., 6 figs., 2 tabs

Effects of excited state mixing on transient absorption spectra in dimers Application to photosynthetic light-harvesting complex II

CERN Document Server

Valkunas, L; Trinkunas, G; Müller, M G; Holzwarth, A R

1999-01-01

The excited state mixing effect is taken into account considering the difference spectra of dimers. Both the degenerate (homo) dimer as well as the nondegenerate (hetero) dimer are considered. Due to the higher excited state mixing with the two-exciton states in the homodimer, the excited state absorption (or the difference spectrum) can be strongly affected in comparison with the results obtained in the Heitler-London approximation. The difference spectrum of the heterodimer is influenced by two resonance effects (i) mixing of the ground state optical transitions of both monomers in the dimer and (ii) mixing of the excited state absorption of the excited monomer with the ground state optical transition in the nonexcited monomer. These effects have been tested by simulating the difference absorption spectra of the light-harvesting complex of photosystem II (LHC II) experimentally obtained with the 60 fs excitation pulses at zero delay times and various excitation wavelengths. The pairs of coupled chlorophylls...

Pulsed laser study of excited states of aromatic molecules absorbed in globular proteins

International Nuclear Information System (INIS)

Cooper, M.; Thomas, J.K.

1977-01-01

Pyrene and several derivatives of pyrene such as pyrene sulfonic acid, and pyrene butyric acid were incorporated into bovine serum albumin (BSA) in aqueous solution. The pyrene chromophore was subsequently excited by a pulse of uv light (lambda = 3471 A) from a Q switched frequency doubled ruby laser. The lifetime of the pyrene excited singlet and triplet states were monitored by time resolved spectrophotometry. Various molecules, such as O 2 and I - , dissolved in the aqueous phase, diffused into the protein and quenched pyrene excited states. The rates of these reactions were followed under a variety of conditions such as pH and temperature and in the presence of inert additives. The rates of pyrene excited-state quenching were often considerably smaller than the rates observed in simple solutions. A comparison of the rates in the protein and homogeneous solutions gives information on the factors such as temperature, charge, and pH that control the movement of small molecules in and into BSA

Protein Structural Deformation Induced Lifetime Shortening of Photosynthetic Bacteria Light-Harvesting Complex LH2 Excited State

OpenAIRE

Chen, Xing-Hai; Zhang, Lei; Weng, Yu-Xiang; Du, Lu-Chao; Ye, Man-Ping; Yang, Guo-Zhen; Fujii, Ritsuko; Rondonuwu, Ferdy S.; Koyama, Yasushi; Wu, Yi-Shi; Zhang, J. P.

2005-01-01

Photosynthetic bacterial light-harvesting antenna complex LH2 was immobilized on the surface of TiO2 nanoparticles in the colloidal solution. The LH2/TiO2 assembly was investigated by the time-resolved spectroscopic methods. The excited-state lifetimes for carotenoid-containing and carotenoidless LH2 have been measured, showing a decrease in the excited-state lifetime of B850 when LH2 was immobilized on TiO2. The possibility that the decrease of the LH2 excited-state lifetime being caused by ...

Electronic properties of excited states in single InAs quantum dots

International Nuclear Information System (INIS)

Warming, Till

2009-01-01

The application of quantum-mechanical effects in semiconductor nanostructures enables the realization of novel opto-electronic devices. Examples are given by single-photon emitters and emitters of entangled photon pairs, both being essential for quantum cryptography, or for qubit systems as needed for quantum computing. InAs/GaAs quantum dots are one of the most promising candidates for such applications. A detailed knowledge of the electronic properties of quantum dots is a prerequisite for this development. The aim of this work is an experimental access to the detailed electronic structure of the excited states in single InAs/GaAs quantum dots including few-particle effects and in particular exchange interaction. The experimental approach is micro photoluminescence excitation spectroscopy (μPLE). One of the main difficulties using μPLE to probe single QDs is the unambiguous assignment of the observed resonances in the spectrum to specific transitions. By comparing micro photoluminescence (μPL) and μPLE spectra, the identification of the main resonances becomes possible. The key is given by the fine structure of the hot trion. Excitation spectroscopy on single charged QDs enables for the first time the complete observation of a non-trivial fine structure of an excitonic complex in a QD, the hot trion. Modelling based on eight-band k.p theory in combination with a configuration interaction scheme is in excellent agreement. Therewith the simulation also enables realistic predictions on the fine structure of the ground-state exciton which is of large importance for single quantum dot devices. Theory concludes from the observed transitions that the structural symmetry of the QDs is broken. Micro photoluminescence excitation spectroscopy combined with resonantly excited micro photoluminescence enables an optical access to the single particle states of the hole without the influence of few-particle coulomb interactions. Based on this knowledge the exciton binding

The separation of vibrational coherence from ground- and excited-electronic states in P3HT film

KAUST Repository

Song, Yin

2015-06-07

© 2015 AIP Publishing LLC. Concurrence of the vibrational coherence and ultrafast electron transfer has been observed in polymer/fullerene blends. However, it is difficult to experimentally investigate the role that the excited-state vibrational coherence plays during the electron transfer process since vibrational coherence from the ground- and excited-electronic states is usually temporally and spectrally overlapped. Here, we performed 2-dimensional electronic spectroscopy (2D ES) measurements on poly(3-hexylthiophene) (P3HT) films. By Fourier transforming the whole 2D ES datasets (S (λ 1, T∼ 2, λ 3)) along the population time (T∼ 2) axis, we develop and propose a protocol capable of separating vibrational coherence from the ground- and excited-electronic states in 3D rephasing and nonrephasing beating maps (S (λ 1, ν∼ 2, λ 3)). We found that the vibrational coherence from pure excited electronic states appears at positive frequency (+ ν∼ 2) in the rephasing beating map and at negative frequency (- ν∼ 2) in the nonrephasing beating map. Furthermore, we also found that vibrational coherence from excited electronic state had a long dephasing time of 244 fs. The long-lived excited-state vibrational coherence indicates that coherence may be involved in the electron transfer process. Our findings not only shed light on the mechanism of ultrafast electron transfer in organic photovoltaics but also are beneficial for the study of the coherence effect on photoexcited dynamics in other systems.

The separation of vibrational coherence from ground- and excited-electronic states in P3HT film

International Nuclear Information System (INIS)

Song, Yin; Hellmann, Christoph; Stingelin, Natalie; Scholes, Gregory D.

2015-01-01

Concurrence of the vibrational coherence and ultrafast electron transfer has been observed in polymer/fullerene blends. However, it is difficult to experimentally investigate the role that the excited-state vibrational coherence plays during the electron transfer process since vibrational coherence from the ground- and excited-electronic states is usually temporally and spectrally overlapped. Here, we performed 2-dimensional electronic spectroscopy (2D ES) measurements on poly(3-hexylthiophene) (P3HT) films. By Fourier transforming the whole 2D ES datasets (S(λ 1 ,T ~ 2 ,λ 3 )) along the population time (T ~ 2 ) axis, we develop and propose a protocol capable of separating vibrational coherence from the ground- and excited-electronic states in 3D rephasing and nonrephasing beating maps (S(λ 1 ,ν ~ 2 ,λ 3 )). We found that the vibrational coherence from pure excited electronic states appears at positive frequency (+ν ~ 2 ) in the rephasing beating map and at negative frequency (−ν ~ 2 ) in the nonrephasing beating map. Furthermore, we also found that vibrational coherence from excited electronic state had a long dephasing time of 244 fs. The long-lived excited-state vibrational coherence indicates that coherence may be involved in the electron transfer process. Our findings not only shed light on the mechanism of ultrafast electron transfer in organic photovoltaics but also are beneficial for the study of the coherence effect on photoexcited dynamics in other systems

Radiative and nonradiative lifetimes in excited states of Ar, Kr and Xe atoms in Ne matrix

International Nuclear Information System (INIS)

Hahn, U.; Schwentner, N.

1979-10-01

Synchrotron radiation with its intense continuum and its excellent time structure has been exploited for time resolved luminescence spectroscopy in the solid state. By selective excitation of n = 1, n' = 1 and n = 2 exciton states of Xe, Kr and Ar atoms in Ne matrix we were able to identify the emitting states involved. Lifetimes within the cascade of radiative and radiationless relaxation between excited states as well as the radiative lifetimes for transitions to the ground state have been derived from the decay curves. Energy positions and radiative lifetimes of the emitting states correspond quite well with those of the free atoms. Radiative and radiationless relaxation processes take place within the manifold of excited states of the guest atoms. The rate constants for radiationless decay confirm an energy gap law. The order of the radiationless processes reaches in some cases extremely high values. Selection rules for spin and angular momentum are essential to understand the observed radiationless transition rates. (orig.)

Computer experiments of the time-sequence of individual steps in multiple Coulomb-excitation

International Nuclear Information System (INIS)

Boer, J. de; Dannhaueser, G.

1982-01-01

The way in which the multiple E2 steps in the Coulomb-excitation of a rotational band of a nucleus follow one another is elucidated for selected examples using semiclassical computer experiments. The role a given transition plays for the excitation of a given final state is measured by a quantity named ''importance function''. It is found that these functions, calculated for the highest rotational state, peak at times forming a sequence for the successive E2 transitions starting from the ground state. This sequential behaviour is used to approximately account for the effects on the projectile orbit of the sequential transfer of excitation energy and angular momentum from projectile to target. These orbits lead to similar deflection functions and cross sections as those obtained from a symmetrization procedure approximately accounting for the transfer of angular momentum and energy. (Auth.)

Inelastic scattering of 9Li and excitation mechanism of its first excited state

International Nuclear Information System (INIS)

Al Falou, H.; Kanungo, R.; Andreoiu, C.; Cross, D.S.; Davids, B.; Djongolov, M.; Gallant, A.T.; Galinski, N.; Howell, D.; Kshetri, R.; Niamir, D.; Orce, J.N.; Shotter, A.C.; Sjue, S.; Tanihata, I.; Thompson, I.J.; Triambak, S.; Uchida, M.; Walden, P.; Wiringa, R.B.

2013-01-01

The first measurement of inelastic scattering of 9 Li from deuterons at the ISAC facility is reported. The measured angular distribution for the first excited state confirms the nature of excitation to be an E2 transition. The quadrupole deformation parameter is extracted from an analysis of the angular distribution

Direct conversion of graphite into diamond through electronic excited states

CERN Document Server

Nakayama, H

2003-01-01

An ab initio total energy calculation has been performed for electronic excited states in diamond and rhombohedral graphite by the full-potential linearized augmented plane wave method within the framework of the local density approximation (LDA). First, calculations for the core-excited state in diamond have been performed to show that the ab initio calculations based on the LDA describe the wavefunctions in the electronic excited states as well as in the ground state quite well. Fairly good coincidence with both experimental data and theoretical prediction has been obtained for the lattice relaxation of the core exciton state. The results of the core exciton state are compared with nitrogen-doped diamond. Next, the structural stability of rhombohedral graphite has been investigated to examine the possibility of the transition into the diamond structure through electronic excited states. While maintaining the rhombohedral symmetry, rhombohedral graphite can be spontaneously transformed to cubic diamond. Tota...

Systematics in Rydberg state excitations for ion-atom collisions

International Nuclear Information System (INIS)

Andresen, B.; Jensen, K.; Petersen, N.B.; Veje, E.

1976-01-01

Rydberg state excitations in the Ne + , Mg + -He collisions have been studied in the projectile energy range 10-75 keV by means of optical spectrometry in a search for systematic trends. The relative excitation cross sections for levels of a Rydberg term series are found to follow a general (nsup(x))sup(P) behaviour with P < approximately -3 varying with collision energy and particles, regardless of whether the excited state population results from direct excitation, single electron transfer, or double electron transfer. At higher collision energies P is approximately -3 as predicted by theory. Polarization of the emitted line radiation indicates that there is no general rule for the relative excitation of the different magnetic substates of the same level. A statistical distribution of excitation is found for levels within the same term when the fine structure splitting is small. (Auth.)

Nonlinear electronic excitations in crystalline solids using meta-generalized gradient approximation and hybrid functional in time-dependent density functional theory

Energy Technology Data Exchange (ETDEWEB)

Sato, Shunsuke A. [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan); Taniguchi, Yasutaka [Center for Computational Science, University of Tsukuba, Tsukuba 305-8571 (Japan); Department of Medical and General Sciences, Nihon Institute of Medical Science, 1276 Shimogawara, Moroyama-Machi, Iruma-Gun, Saitama 350-0435 (Japan); Shinohara, Yasushi [Max Planck Institute of Microstructure Physics, 06120 Halle (Germany); Yabana, Kazuhiro [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan); Center for Computational Science, University of Tsukuba, Tsukuba 305-8571 (Japan)

2015-12-14

We develop methods to calculate electron dynamics in crystalline solids in real-time time-dependent density functional theory employing exchange-correlation potentials which reproduce band gap energies of dielectrics; a meta-generalized gradient approximation was proposed by Tran and Blaha [Phys. Rev. Lett. 102, 226401 (2009)] (TBm-BJ) and a hybrid functional was proposed by Heyd, Scuseria, and Ernzerhof [J. Chem. Phys. 118, 8207 (2003)] (HSE). In time evolution calculations employing the TB-mBJ potential, we have found it necessary to adopt the predictor-corrector step for a stable time evolution. We have developed a method to evaluate electronic excitation energy without referring to the energy functional which is unknown for the TB-mBJ potential. For the HSE functional, we have developed a method for the operation of the Fock-like term in Fourier space to facilitate efficient use of massive parallel computers equipped with graphic processing units. We compare electronic excitations in silicon and germanium induced by femtosecond laser pulses using the TB-mBJ, HSE, and a simple local density approximation (LDA). At low laser intensities, electronic excitations are found to be sensitive to the band gap energy: they are close to each other using TB-mBJ and HSE and are much smaller in LDA. At high laser intensities close to the damage threshold, electronic excitation energies do not differ much among the three cases.

Assessment of time-dependent density functional theory with the restricted excitation space approximation for excited state calculations of large systems

Science.gov (United States)

Hanson-Heine, Magnus W. D.; George, Michael W.; Besley, Nicholas A.

2018-06-01

The restricted excitation subspace approximation is explored as a basis to reduce the memory storage required in linear response time-dependent density functional theory (TDDFT) calculations within the Tamm-Dancoff approximation. It is shown that excluding the core orbitals and up to 70% of the virtual orbitals in the construction of the excitation subspace does not result in significant changes in computed UV/vis spectra for large molecules. The reduced size of the excitation subspace greatly reduces the size of the subspace vectors that need to be stored when using the Davidson procedure to determine the eigenvalues of the TDDFT equations. Furthermore, additional screening of the two-electron integrals in combination with a reduction in the size of the numerical integration grid used in the TDDFT calculation leads to significant computational savings. The use of these approximations represents a simple approach to extend TDDFT to the study of large systems and make the calculations increasingly tractable using modest computing resources.

Excited states in 146Sm and 147Sm

International Nuclear Information System (INIS)

Kownacki, J.; Sujkowski, Z.; Hammaren, E.; Liukkonen, E.; Piiparinen, M.; Lindblad, Th.; Ryde, H.

1979-10-01

The sup(144,146)Nd(α,xn) and sup(146,148)Nd( 3 He,xn) reactions with Esub(α) = 20 - 43 MeV and E 3 sub(He) = 19 - 27 MeV are used to investigate excited states in the isotopes 146 Sm and 147 Sm. The experiments involve measurements of singles γ-ray spectra and conversion electron spectra, γ-ray angular distributions and three parameter (E sub(γ)E sub(γ) time) coincidences. From these experiments information is obtained for states with spin up to I = 13 + and I = 27/2 - , respectively, These states are interpeted within the framework of the cluster-vibration model (CVM) as well as the shell model. (author)

σ-SCF: A direct energy-targeting method to mean-field excited states.

Science.gov (United States)

Ye, Hong-Zhou; Welborn, Matthew; Ricke, Nathan D; Van Voorhis, Troy

2017-12-07

The mean-field solutions of electronic excited states are much less accessible than ground state (e.g., Hartree-Fock) solutions. Energy-based optimization methods for excited states, like Δ-SCF (self-consistent field), tend to fall into the lowest solution consistent with a given symmetry-a problem known as "variational collapse." In this work, we combine the ideas of direct energy-targeting and variance-based optimization in order to describe excited states at the mean-field level. The resulting method, σ-SCF, has several advantages. First, it allows one to target any desired excited state by specifying a single parameter: a guess of the energy of that state. It can therefore, in principle, find all excited states. Second, it avoids variational collapse by using a variance-based, unconstrained local minimization. As a consequence, all states-ground or excited-are treated on an equal footing. Third, it provides an alternate approach to locate Δ-SCF solutions that are otherwise hardly accessible by the usual non-aufbau configuration initial guess. We present results for this new method for small atoms (He, Be) and molecules (H 2 , HF). We find that σ-SCF is very effective at locating excited states, including individual, high energy excitations within a dense manifold of excited states. Like all single determinant methods, σ-SCF shows prominent spin-symmetry breaking for open shell states and our results suggest that this method could be further improved with spin projection.

Analytic energy gradient of excited electronic state within TDDFT/MMpol framework: Benchmark tests and parallel implementation.

Science.gov (United States)

Zeng, Qiao; Liang, WanZhen

2015-10-07

The time-dependent density functional theory (TDDFT) has become the most popular method to calculate the electronic excitation energies, describe the excited-state properties, and perform the excited-state geometric optimization of medium and large-size molecules due to the implementation of analytic excited-state energy gradient and Hessian in many electronic structure software packages. To describe the molecules in condensed phase, one usually adopts the computationally efficient hybrid Quantum Mechanics/Molecular Mechanics (QM/MM) models. Here, we extend our previous work on the energy gradient of TDDFT/MM excited state to account for the mutual polarization effects between QM and MM regions, which is believed to hold a crucial position in the potential energy surface of molecular systems when the photoexcitation-induced charge rearrangement in the QM region is drastic. The implementation of a simple polarizable TDDFT/MM (TDDFT/MMpol) model in Q-Chem/CHARMM interface with both the linear response and the state-specific features has been realized. Several benchmark tests and preliminary applications are exhibited to confirm our implementation and assess the effects of different treatment of environmental polarization on the excited-state properties, and the efficiency of parallel implementation is demonstrated as well.

Excited state conformational dynamics in carotenoids: dark intermediates and excitation energy transfer.

Science.gov (United States)

Beck, Warren F; Bishop, Michael M; Roscioli, Jerome D; Ghosh, Soumen; Frank, Harry A

2015-04-15

A consideration of the excited state potential energy surfaces of carotenoids develops a new hypothesis for the nature of the conformational motions that follow optical preparation of the S2 (1(1)Bu(+)) state. After an initial displacement from the Franck-Condon geometry along bond length alternation coordinates, it is suggested that carotenoids pass over a transition-state barrier leading to twisted conformations. This hypothesis leads to assignments for several dark intermediate states encountered in femtosecond spectroscopic studies. The Sx state is assigned to the structure reached upon the onset of torsional motions near the transition state barrier that divides planar and twisted structures on the S2 state potential energy surface. The X state, detected recently in two-dimensional electronic spectra, corresponds to a twisted structure well past the barrier and approaching the S2 state torsional minimum. Lastly, the S(∗) state is assigned to a low lying S1 state structure with intramolecular charge transfer character (ICT) and a pyramidal conformation. It follows that the bent and twisted structures of carotenoids that are found in photosynthetic light-harvesting proteins yield excited-state structures that favor the development of an ICT character and optimized energy transfer yields to (bacterio)chlorophyll acceptors. Copyright © 2015 Elsevier Inc. All rights reserved.

New Theoretical Developments in Exploring Electronically Excited States: Including Localized Configuration Interaction Singles and Application to Large Helium Clusters

Science.gov (United States)

Closser, Kristina Danielle

This thesis presents new developments in excited state electronic structure theory. Contrasted with the ground state, the electronically excited states of atoms and molecules often are unstable and have short lifetimes, exhibit a greater diversity of character and are generally less well understood. The very unusual excited states of helium clusters motivated much of this work. These clusters consist of large numbers of atoms (experimentally 103--109 atoms) and bands of nearly degenerate excited states. For an isolated atom the lowest energy excitation energies are from 1s → 2s and 1s → 2 p transitions, and in clusters describing the lowest energy band minimally requires four states per atom. In the ground state the clusters are weakly bound by van der Waals interactions, however in the excited state they can form well-defined covalent bonds. The computational cost of quantum chemical calculations rapidly becomes prohibitive as the size of the systems increase. Standard excited-state methods such as configuration interaction singles (CIS) and time-dependent density functional theory (TD-DFT) can be used with ≈100 atoms, and are optimized to treat only a few states. Thus, one of our primary aims is to develop a method which can treat these large systems with large numbers of nearly degenerate excited states. Additionally, excited states are generally formed far from their equilibrium structures. Vertical excitations from the ground state induce dynamics in the excited states. Thus, another focus of this work is to explore the results of these forces and the fate of the excited states. Very little was known about helium cluster excited states when this work began, thus we first investigated the excitations in small helium clusters consisting of 7 or 25 atoms using CIS. The character of these excited states was determined using attachment/detachment density analysis and we found that in the n = 2 manifold the excitations could generally be interpreted as

From fusion hierarchy to excited state TBA

International Nuclear Information System (INIS)

Juettner, G.; Kluemper, A.

1998-01-01

Functional relations among the fusion hierarchy of quantum transfer matrices give a novel derivation of the TBA equations, namely without string hypothesis. This is demonstrated for two important models of 1D highly correlated electron systems, the supersymmetric t-J model and the supersymmetric extended Hubbard model. As a consequence, ''the excited state TBA'' equations, which characterize correlation lengths, are explicitly derived for the t-J model. To the authors' knowledge, this is the first explicit derivation of excited state TBA equations for 1D lattice electron systems. (orig.)

Time evolution, Lamb shift, and emission spectra of spontaneous emission of two identical atoms

International Nuclear Information System (INIS)

Wang Dawei; Li Zhenghong; Zheng Hang; Zhu Shiyao

2010-01-01

A unitary transformation method is used to investigate the dynamic evolution of two multilevel atoms, in the basis of symmetric and antisymmetric states, with one atom being initially prepared in the first excited state and the other in the ground state. The unitary transformation guarantees that our calculations are based on the ground state of the atom-field system and the self-energy is subtracted at the beginning. The total Lamb shifts of the symmetric and antisymmetric states are divided into transformed shift and dynamic shift. The transformed shift is due to emitting and reabsorbing of virtual photons, by a single atom (nondynamic single atomic shift) and between the two atoms (quasi-static shift). The dynamic shift is due to the emitting and reabsorbing of real photons, by a single atom (dynamic single atomic shift) and between the two atoms (dynamic interatomic shift). The emitting and reabsorbing of virtual and real photons between the two atoms result in the interatomic shift, which does not exist for the one-atom case. The spectra at the long-time limit are calculated. If the distance between the two atoms is shorter than or comparable to the wavelength, the strong coupling between the two atoms splits the spectrum into two peaks, one from the symmetric state and the other from the antisymmetric state. The origin of the red or blue shifts for the symmetric and antisymmetric states mainly lies in the negative or positive interaction energy between the two atoms. In the investigation of the short time evolution, we find the modification of the effective density of states by the interaction between two atoms can modulate the quantum Zeno and quantum anti-Zeno effects in the decays of the symmetric and antisymmetric states.

Dynamics of Excited State Proton Transfer in Nitro Substituted 10-Hydroxybenzo[h]quinolines

DEFF Research Database (Denmark)

Marciak, H; Hristova, S.; Deneva, V

2017-01-01

The ground state tautomerism and excited state intramolecular proton transfer (ESIPT) of 10-hydroxybenzo[h]quinoline (HBQ) and its nitro derivatives, 7-nitrobenzo[h]quinolin-10-ol (2) and 7,9-dinitrobenzo[h]quinolin-10-ol (3), have been studied in acetonitrile using steady state as well as time d...

Method of producing excited states of atomic nuclei

International Nuclear Information System (INIS)

Morita, M.; Morita, R.

1976-01-01

A method is claimed of producing excited states of atomic nuclei which comprises bombarding atoms with x rays or electrons, characterized in that (1) in the atoms selected to be produced in the excited state of their nuclei, (a) the difference between the nuclear excitation energy and the difference between the binding energies of adequately selected two electron orbits is small enough to introduce the nuclear excitation by electron transition, and (b) the system of the nucleus and the electrons in the case of ionizing an orbital electron in said atoms should satisfy the spin and parity conservation laws; and (2) the energy of the bombarding x rays or electrons should be larger than the binding energy of one of the said two electron orbits which is located at shorter distance from the atomic nucleus. According to the present invention, atomic nuclei can be excited in a relatively simple manner without requiring the use of large scale apparatus, equipment and production facilities, e.g., factories. It is also possible to produce radioactive substances or separate a particular isotope with an extremely high purity from a mixture of isotopes by utilizing nuclear excitation

Electron impact excitation of the lowest doublet and quartet core-excited autoionizing states in Rb atoms

International Nuclear Information System (INIS)

Borovik, A; Roman, V; Zatsarinny, O; Bartschat, K

2013-01-01

Electron impact excitation of the (4p 5 5s 2 ) 2 P 3/2,1/2 and (4p 5 4d5s) 4 P 1/2,3/2,5/2 autoionizing states in rubidium atoms was studied experimentally by measuring the ejected-electron excitation functions and theoretically by employing a fully relativistic Dirac B-spline R-matrix (close-coupling) model. The experimental data were collected in an impact energy range from the respective excitation thresholds up to 50 eV with an incident electron energy resolution of 0.2 eV and an observation angle of 54.7°. Absolute values of the excitation cross sections were obtained by normalizing to the theoretical predictions. The observed near-threshold resonance structures were also analysed by comparison with theory. For the 2 P 3/2,1/2 doublet states, a detailed analysis of the R-matrix results reveals that the most intense resonances are related to odd-parity negative-ion states with dominant configurations 4p 5 5s5p 2 and 4p 5 4d5s6s. The measured excitation functions for the 2 P 1/2 and 4 P J states indicate a noticeable cascade population due to the radiative decay from high-lying autoionizing states. A comparative analysis with similar data for other alkali atoms is also presented.

Nonadiabatic excited-state molecular dynamics: On-the-fly limiting of essential excited states

Energy Technology Data Exchange (ETDEWEB)

Nelson, Tammie [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Naumov, Artem [Skolkovo Institute of Science and Technology, Moscow 143026 (Russian Federation); Fernandez-Alberti, Sebastian [Universidad Nacional de Quilmes, Roque Saenz Pea 352, B1876BXD Bernal (Argentina); Tretiak, Sergei, E-mail: serg@lanl.gov [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2016-12-20

The simulation of nonadiabatic dynamics in extended molecular systems involving hundreds of atoms and large densities of states is particularly challenging. Nonadiabatic coupling terms (NACTs) represent a significant numerical bottleneck in surface hopping approaches. Rather than using unreliable NACT cutting schemes, here we develop “on-the-fly” state limiting methods to eliminate states that are no longer essential for the non-radiative relaxation dynamics as a trajectory proceeds. We propose a state number criteria and an energy-based state limit. The latter is more physically relevant by requiring a user-imposed energy threshold. For this purpose, we introduce a local kinetic energy gauge by summing contributions from atoms within the spatial localization of the electronic wavefunction to define the energy available for upward hops. The proposed state limiting schemes are implemented within the nonadiabatic excited-state molecular dynamics framework to simulate photoinduced relaxation in poly-phenylene vinylene (PPV) and branched poly-phenylene ethynylene (PPE) oligomers for benchmark evaluation.

Excited state populations and charge-exchange of fast ions in solids

International Nuclear Information System (INIS)

Miller, P.D.; Sofield, C.J.; Woods, C.J.

1984-01-01

Excited state populations and charge state fractions of 445 MeV Cl ions have been measured for a range of thicknesses of solid C targets. Cross sections for electron capture, loss, excitation and excited state quenching have been determined and these data are found to predict a quantitative difference between equilibrium charge state distributions from gases and solids for a special case of the Bohr-Lindhard density effect model. 8 references, 1 figure, 1 table

Excited states of open strings from N=4 SYM

International Nuclear Information System (INIS)

Dzienkowski, Eric

2015-01-01

We continue the analysis of building open strings stretched between giant gravitons from N=4 SYM by going to second order in perturbation theory using the three-loop dilatation generator from the field theory. In the process we build a Fock-like space of states using Cuntz oscillators which can be used to access the excited open string states. We find a remarkable cancellation among the excited states that shows the ground state energy is consistent with a fully relativistic dispersion relation.

σ-SCF: A direct energy-targeting method to mean-field excited states

Science.gov (United States)

Ye, Hong-Zhou; Welborn, Matthew; Ricke, Nathan D.; Van Voorhis, Troy

2017-12-01

The mean-field solutions of electronic excited states are much less accessible than ground state (e.g., Hartree-Fock) solutions. Energy-based optimization methods for excited states, like Δ-SCF (self-consistent field), tend to fall into the lowest solution consistent with a given symmetry—a problem known as "variational collapse." In this work, we combine the ideas of direct energy-targeting and variance-based optimization in order to describe excited states at the mean-field level. The resulting method, σ-SCF, has several advantages. First, it allows one to target any desired excited state by specifying a single parameter: a guess of the energy of that state. It can therefore, in principle, find all excited states. Second, it avoids variational collapse by using a variance-based, unconstrained local minimization. As a consequence, all states—ground or excited—are treated on an equal footing. Third, it provides an alternate approach to locate Δ-SCF solutions that are otherwise hardly accessible by the usual non-aufbau configuration initial guess. We present results for this new method for small atoms (He, Be) and molecules (H2, HF). We find that σ-SCF is very effective at locating excited states, including individual, high energy excitations within a dense manifold of excited states. Like all single determinant methods, σ-SCF shows prominent spin-symmetry breaking for open shell states and our results suggest that this method could be further improved with spin projection.

Shaping charge excitations in chiral edge states with a time-dependent gate voltage

Science.gov (United States)

Misiorny, Maciej; Fève, Gwendal; Splettstoesser, Janine

2018-02-01

We study a coherent conductor supporting a single edge channel in which alternating current pulses are created by local time-dependent gating and sent on a beam-splitter realized by a quantum point contact. The current response to the gate voltage in this setup is intrinsically linear. Based on a fully self-consistent treatment employing a Floquet scattering theory, we analyze the effect of different voltage shapes and frequencies, as well as the role of the gate geometry on the injected signal. In particular, we highlight the impact of frequency-dependent screening on the process of shaping the current signal. The feasibility of creating true single-particle excitations with this method is confirmed by investigating the suppression of excess noise, which is otherwise created by additional electron-hole pair excitations in the current signal.

Mesoscopic structural phase progression in photo-excited VO2 revealed by time-resolved x-ray diffraction microscopy

Science.gov (United States)

Zhu, Yi; Cai, Zhonghou; Chen, Pice; Zhang, Qingteng; Highland, Matthew J.; Jung, Il Woong; Walko, Donald A.; Dufresne, Eric M.; Jeong, Jaewoo; Samant, Mahesh G.; Parkin, Stuart S. P.; Freeland, John W.; Evans, Paul G.; Wen, Haidan

2016-02-01

Dynamical phase separation during a solid-solid phase transition poses a challenge for understanding the fundamental processes in correlated materials. Critical information underlying a phase transition, such as localized phase competition, is difficult to reveal by measurements that are spatially averaged over many phase separated regions. The ability to simultaneously track the spatial and temporal evolution of such systems is essential to understanding mesoscopic processes during a phase transition. Using state-of-the-art time-resolved hard x-ray diffraction microscopy, we directly visualize the structural phase progression in a VO2 film upon photoexcitation. Following a homogenous in-plane optical excitation, the phase transformation is initiated at discrete sites and completed by the growth of one lattice structure into the other, instead of a simultaneous isotropic lattice symmetry change. The time-dependent x-ray diffraction spatial maps show that the in-plane phase progression in laser-superheated VO2 is via a displacive lattice transformation as a result of relaxation from an excited monoclinic phase into a rutile phase. The speed of the phase front progression is quantitatively measured, and is faster than the process driven by in-plane thermal diffusion but slower than the sound speed in VO2. The direct visualization of localized structural changes in the time domain opens a new avenue to study mesoscopic processes in driven systems.

Inelastic scattering of {sup 9}Li and excitation mechanism of its first excited state

Energy Technology Data Exchange (ETDEWEB)

Al Falou, H. [Astronomy and Physics Department, Saint Mary' s University, Halifax, Nova Scotia B3H 3C3 (Canada); TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Kanungo, R., E-mail: ritu@triumf.ca [Astronomy and Physics Department, Saint Mary' s University, Halifax, Nova Scotia B3H 3C3 (Canada); Andreoiu, C.; Cross, D.S. [Department of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada); Davids, B.; Djongolov, M. [TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Gallant, A.T. [TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Department of Physics, University of British Columbia, British Columbia V6T 1Z4 (Canada); Galinski, N.; Howell, D. [TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada); Kshetri, R.; Niamir, D. [TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Orce, J.N. [TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Department of Physics, University of the Western Cape, P/B X17, Bellville, ZA-7535 (South Africa); Shotter, A.C. [Department of Physics and Astronomy, University of Edinburgh, Edinburgh (United Kingdom); Sjue, S. [TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Tanihata, I. [Research Center for Nuclear Physics, Osaka University, Mihogaoka, Ibaraki, Osaka 567 0047 (Japan); Thompson, I.J. [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Triambak, S. [TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Uchida, M. [Astronomy and Physics Department, Saint Mary' s University, Halifax, Nova Scotia B3H 3C3 (Canada); Walden, P. [TRIUMF, Vancouver, British Columbia V6T 2A3 (Canada); Wiringa, R.B. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States)

2013-04-25

The first measurement of inelastic scattering of {sup 9}Li from deuterons at the ISAC facility is reported. The measured angular distribution for the first excited state confirms the nature of excitation to be an E2 transition. The quadrupole deformation parameter is extracted from an analysis of the angular distribution.

Critical Assessment of TD-DFT for Excited States of Open-Shell Systems: I. Doublet-Doublet Transitions.

Science.gov (United States)

Li, Zhendong; Liu, Wenjian

2016-01-12

A benchmark set of 11 small radicals is set up to assess the performance of time-dependent density functional theory (TD-DFT) for the excited states of open-shell systems. Both the unrestricted (U-TD-DFT) and spin-adapted (X-TD-DFT) formulations of TD-DFT are considered. For comparison, the well-established EOM-CCSD (equation-of-motion coupled-cluster with singles and doubles) is also used. In total, 111 low-lying singly excited doublet states are accessed by all the three approaches. Taking the MRCISD+Q (multireference configuration interaction with singles and doubles plus the Davidson correction) results as the benchmark, it is found that both U-TD-DFT and EOM-CCSD perform well for those states dominated by singlet-coupled single excitations (SCSE) from closed-shell to open-shell, open-shell to vacant-shell, or closed-shell to vacant-shell orbitals. However, for those states dominated by triplet-coupled single excitations (TCSE) from closed-shell to vacant-shell orbitals, both U-TD-DFT and EOM-CCSD fail miserably due to severe spin contaminations. In contrast, X-TD-DFT provides balanced descriptions of both SCSE and TCSE. As far as the functional dependence is concerned, it is found that, when the Hartree-Fock ground state does not suffer from the instability problem, both global hybrid (GH) and range-separated hybrid (RSH) functionals perform grossly better than pure density functionals, especially for Rydberg and charge-transfer excitations. However, if the Hartree-Fock ground state is instable or nearly instable, GH and RSH tend to underestimate severely the excitation energies. The SAOP (statistically averaging of model orbital potentials) performs more uniformly than any other density functionals, although it generally overestimates the excitation energies of valence excitations. Not surprisingly, both EOM-CCSD and adiabatic TD-DFT are incapable of describing excited states with substantial double excitation characters.

Lifetime and g-factor measurements of excited states using Coulomb excitation and alpha transfer reactions

Energy Technology Data Exchange (ETDEWEB)

Guevara, Z. E., E-mail: zjguevaram@unal.edu.co; Torres, D. A., E-mail: datorresg@unal.edu.co [Physics Department, Universidad Nacional de Colombia, Bogotá D.C. (Colombia)

2016-07-07

In this contribution the challenges in the use of a setup to simultaneously measure lifetimes and g-factor values will be presented. The simultaneous use of the transient field technique and the Doppler Shift Attenuation Method, to measure magnetic moments and lifetimes respectively, allows to obtain a complete characterization of the currents of nucleons and the deformation in excited states close to the ground state. The technique is at the moment limited to Coulomb excitation and alpha-transfer reactions, what opens an interesting perspective to consider this type of experiments with radioactive beams. The use of deep-inelastic and fusion-evaporation reactions will be discussed. An example of a setup that makes use of a beam of {sup 106}Cd to study excited states of {sup 110}Sn and the beam nuclei itself will be presented.

The Sommerfeld enhancement for dark matter with an excited state

International Nuclear Information System (INIS)

Slatyer, Tracy R.

2010-01-01

We present an analysis of the Sommerfeld enhancement to dark matter annihilation in the presence of an excited state, where the interaction inducing the enhancement is purely off-diagonal, such as in models of exciting or inelastic dark matter. We derive a simple and accurate semi-analytic approximation for the s-wave enhancement, which is valid provided the mass splitting between the ground and excited states is not too large, and discuss the cutoff of the enhancement for large mass splittings. We reproduce previously derived results in the appropriate limits, and demonstrate excellent agreement with numerical calculations of the enhancement. We show that the presence of an excited state leads to generically larger values of the Sommerfeld enhancement, larger resonances, and shifting of the resonances to lower mediator masses. Furthermore, in the presence of a mass splitting the enhancement is no longer a monotonic function of velocity: the enhancement where the kinetic energy is close to that required to excite the higher state can be up to twice as large as the enhancement at zero velocity

The excited states of 79Kr

International Nuclear Information System (INIS)

Liptak, J.; Kristiak, J.; Kristiakova, K.

1977-01-01

The β + -decay of 79 Rb has been studied with Ge(Li) detectors in single and coincidence modes. The half-life of the 147.06 keV level in 79 Kr has been determined to be (78+-6) ns. The relative electron intensities of seventeen transitions have been measured with a magnetic Si(Li) spectrometer. The internal conversion coefficients have been determined. The transition multipolarities have been deduced. The spin-parity assignments have been made for excited states of 79 Kr and a β-decaying sta 79 Rb(5/2 + ). The structure of excited states in 79 Kr is discussed in the framework of the Alaga and Coriolis coupling models. It is shown that the properties of some levels in 79 Kr can be explained by the existence of relatively pure rotational bands

Excited state electron affinity calculations for aluminum

Science.gov (United States)

Hussein, Adnan Yousif

2017-08-01

Excited states of negative aluminum ion are reviewed, and calculations of electron affinities of the states (3s^23p^2)^1D and (3s3p^3){^5}{S}° relative to the (3s^23p)^2P° and (3s3p^2)^4P respectively of the neutral aluminum atom are reported in the framework of nonrelativistic configuration interaction (CI) method. A priori selected CI (SCI) with truncation energy error (Bunge in J Chem Phys 125:014107, 2006) and CI by parts (Bunge and Carbó-Dorca in J Chem Phys 125:014108, 2006) are used to approximate the valence nonrelativistic energy. Systematic studies of convergence of electron affinity with respect to the CI excitation level are reported. The calculated value of the electron affinity for ^1D state is 78.675(3) meV. Detailed Calculations on the ^5S°c state reveals that is 1216.8166(3) meV below the ^4P state.

Nested variant of the method of moments of coupled cluster equations for vertical excitation energies and excited-state potential energy surfaces.

Science.gov (United States)

Kowalski, Karol

2009-05-21

In this article we discuss the problem of proper balancing of the noniterative corrections to the ground- and excited-state energies obtained with approximate coupled cluster (CC) and equation-of-motion CC (EOMCC) approaches. It is demonstrated that for a class of excited states dominated by single excitations and for states with medium doubly excited component, the newly introduced nested variant of the method of moments of CC equations provides mathematically rigorous way of balancing the ground- and excited-state correlation effects. The resulting noniterative methodology accounting for the effect of triples is tested using its parallel implementation on the systems, for which iterative CC/EOMCC calculations with full inclusion of triply excited configurations or their most important subset are numerically feasible.

Solvent-dependent excited-state hydrogen transfer and intersystem crossing in 2-(2′-hydroxyphenyl)-benzothiazole

KAUST Repository

Aly, Shawkat Mohammede

2015-02-12

The excited-state intramolecular hydrogen transfer (ESIHT) of 2-(2′-hydroxyphenyl) benzothiazole (HBT) has been investigated in a series of nonpolar, polar aprotic, and polar protic solvents. A variety of state-of-the-art experimental methods were employed, including femto- and nanosecond transient absorption and fluorescence upconversion spectroscopy with broadband capabilities. We show that the dynamics and mechanism of ESIHT of the singlet excited HBT are strongly solvent-dependent. In nonpolar solvents, the data demonstrate that HBT molecules adopt a closed form stabilized by O-H⋯N chelated hydrogen bonds with no twisting angle, and the photoinduced H transfer occurs within 120 fs, leading to the formation of a keto tautomer. In polar solvents, owing to dipole-dipole cross talk and hydrogen bonding interactions, the H transfer process is followed by ultrafast nonradiative deactivation channels, including ultrafast internal conversion (IC) and intersystem crossing (ISC). This is likely to be driven by the twisting motion around the C-C bond between the hydroxyphenyl and thiazole moieties, facilitating the IC back to the enol ground state or to the keto triplet state. In addition, our femtosecond time-resolved fluorescence experiments indicate, for the first time, that the lifetime of the enol form in ACN is approximately 280 fs. This observation indicates that the solvent plays a crucial role in breaking the H bond and deactivating the excited state of the HBT. Interestingly, the broadband transient absorption and fluorescence up-conversion data clearly demonstrate that the intermolecular proton transfer from the excited HBT to the DMSO solvent is about 190 fs, forming the HBT anion excited state.

Solvent-dependent excited-state hydrogen transfer and intersystem crossing in 2-(2′-hydroxyphenyl)-benzothiazole

KAUST Repository

Aly, Shawkat Mohammede; Usman, Anwar; Alzayer, Maytham; Hamdi, Ghada A.; Alarousu, Erkki; Mohammed, Omar F.

2015-01-01

The excited-state intramolecular hydrogen transfer (ESIHT) of 2-(2′-hydroxyphenyl) benzothiazole (HBT) has been investigated in a series of nonpolar, polar aprotic, and polar protic solvents. A variety of state-of-the-art experimental methods were employed, including femto- and nanosecond transient absorption and fluorescence upconversion spectroscopy with broadband capabilities. We show that the dynamics and mechanism of ESIHT of the singlet excited HBT are strongly solvent-dependent. In nonpolar solvents, the data demonstrate that HBT molecules adopt a closed form stabilized by O-H⋯N chelated hydrogen bonds with no twisting angle, and the photoinduced H transfer occurs within 120 fs, leading to the formation of a keto tautomer. In polar solvents, owing to dipole-dipole cross talk and hydrogen bonding interactions, the H transfer process is followed by ultrafast nonradiative deactivation channels, including ultrafast internal conversion (IC) and intersystem crossing (ISC). This is likely to be driven by the twisting motion around the C-C bond between the hydroxyphenyl and thiazole moieties, facilitating the IC back to the enol ground state or to the keto triplet state. In addition, our femtosecond time-resolved fluorescence experiments indicate, for the first time, that the lifetime of the enol form in ACN is approximately 280 fs. This observation indicates that the solvent plays a crucial role in breaking the H bond and deactivating the excited state of the HBT. Interestingly, the broadband transient absorption and fluorescence up-conversion data clearly demonstrate that the intermolecular proton transfer from the excited HBT to the DMSO solvent is about 190 fs, forming the HBT anion excited state.

Resonant excitation and the decay of autoionization states in a strong electromagnetic field

International Nuclear Information System (INIS)

Andryushin, A.I.; Kazakov, A.E.; Fedorov, M.V.

1985-01-01

Photoionization of atoms involving resonant excitation of the auto-ionization state is studied. The evolution of the total ionization probability, its dependence on the frequency of the resonance radiation and also the photoelectron energy spectrum are investigated. It is shown that the energy of the final state of the system may be localized either in the vicinity of E approximately Esub(α), where Esub(α) is the auto-ionization energy, or in the vicinity of E approximately Esub(α)+h/2πω where h/2πω is the quantum energy of the resonance radiation. The photoelectron specturum in the region E approximately Esub(α)+h/2πω as a whole is similar to the electron spectrum on photoionization of atoms involving resonance excitation of the bound state. A strong effect on the photoelectron spectrum in the region E approximately Esub(α) is exerted by interference of various decay channels of the ground state in the resonance field which leads to the appearance in the spectrum of a characteristic structure of the Fano type. Interence also affects the widths of the two spectral curves, the relatve amount of electrons in the two energy ranges and also other characteristics of the ionization process. It is shown that the presence of a noninterfering photoionization channel of the autoionization state ensures the finiteness of the swidths and heights of the spectral curves and the absence of complete ''coherency merging''

Evolution of collectivity in the 78Ni region: Coulomb excitation of 74Ni at intermediate energies.

Directory of Open Access Journals (Sweden)

Marchi T.

2014-03-01

Full Text Available The study of the collective properties of nuclear excitations far from stability provides information about the shell structure at extreme conditions. Spectroscopic observables such as the energy or the transition probabilities of the lowest states, in nuclei with large neutron excess, allow to probe the density and isospin dependence of the effective interaction. Indeed, it was recently shown that tensor and three-body forces play an important role in breaking and creating magic numbers. Emblematic is the case of the evolution of the Ni isotopic chain where several features showed up moving from the most neutron rich stable isotope (64Ni towards the 78Ni nucleus where the large neutron excess coincides with a double shell closure. In this framework, we have recently performed an experiment with the goal to extract the B(E2; 0+ → 2+ value for the 74Ni nucleus in an intermediate-energy Coulomb excitation experiment: preliminary results are discussed.

Recurrence of the excited states of nuclei and time coherency of the de Broglie wave in 16O+n resonances

International Nuclear Information System (INIS)

Ohkubo, Makio

2003-01-01

From the requirement of the time periodicity of a (quasi) stable state, frequencies of the normal modes, which compose the state, are commensurable (integer ratios) with each other, and the excitation energies E x are written as a sum of inverse integers. We propose an expression: E x = GΣ1/n, where n = integers and G = 34.5 MeV. Recurrence time is defined as LCM(n j ) x τ o , where τ 0 = 2πℎ/G = 1.20 x 10 -22 s. LCM vs. E x are illustrated for all possible n j of 2 and 3 normal modes. In 16 O +n resonances, integer ratios are found between the recurrence frequencies of 17 O and the de Broglie wave frequencies of incident neutron, meaning time coherency between them. A simple branch pattern is found in 16 O +n resonance levels. (author)

Doubly and triply excited states for different plasma sources

International Nuclear Information System (INIS)

More, R.M.; Safronova, U.I.

2000-01-01

Autoionizing rates of doubly excited states as nln'l' configurations with n=2-9 and n'=2-9 are calculated. Analytical expressions of decay amplitude for two-electron system are derived. Expressions for autoionizing rates with averaging over LS are obtained for many-electron systems. The n and l dependence of doubly excited states as nln'l' configurations are investigated. (author)

Benchmarking the stochastic time-dependent variational approach for excitation dynamics in molecular aggregates

Energy Technology Data Exchange (ETDEWEB)

Chorošajev, Vladimir [Department of Theoretical Physics, Faculty of Physics, Vilnius University, Sauletekio 9-III, 10222 Vilnius (Lithuania); Gelzinis, Andrius; Valkunas, Leonas [Department of Theoretical Physics, Faculty of Physics, Vilnius University, Sauletekio 9-III, 10222 Vilnius (Lithuania); Department of Molecular Compound Physics, Center for Physical Sciences and Technology, Sauletekio 3, 10222 Vilnius (Lithuania); Abramavicius, Darius, E-mail: darius.abramavicius@ff.vu.lt [Department of Theoretical Physics, Faculty of Physics, Vilnius University, Sauletekio 9-III, 10222 Vilnius (Lithuania)

2016-12-20

Highlights: • The Davydov ansatze can be used for finite temperature simulations with an extension. • The accuracy is high if the system is strongly coupled to the environmental phonons. • The approach can simulate time-resolved fluorescence spectra. - Abstract: Time dependent variational approach is a convenient method to characterize the excitation dynamics in molecular aggregates for different strengths of system-bath interaction a, which does not require any additional perturbative schemes. Until recently, however, this method was only applicable in zero temperature case. It has become possible to extend this method for finite temperatures with the introduction of stochastic time dependent variational approach. Here we present a comparison between this approach and the exact hierarchical equations of motion approach for describing excitation dynamics in a broad range of temperatures. We calculate electronic population evolution, absorption and auxiliary time resolved fluorescence spectra in different regimes and find that the stochastic approach shows excellent agreement with the exact approach when the system-bath coupling is sufficiently large and temperatures are high. The differences between the two methods are larger, when temperatures are lower or the system-bath coupling is small.

Describing excited state relaxation and localization in TiO2 nanoparticles using TD-DFT

International Nuclear Information System (INIS)

Berardo, Enrico; Hu, Han-Shi; Van Dam, Hubertus J. J.; Shevlin, Stephen A.; Woodley, Scott M.; Kowalski, Karol; Zwijnenburg, Martijn A.

2014-01-01

We have investigated the description of excited state relaxation in naked and hydrated TiO 2 nanoparticles using Time-Dependent Density Functional Theory (TD-DFT) with three common hybrid exchange-correlation (XC) potentials; B3LYP, CAM-B3LYP and BHLYP. Use of TD-CAM-B3LYP and TD-BHLYP yields qualitatively similar results for all structures, which are also consistent with predictions of coupled cluster theory for small particles. TD-B3LYP, in contrast, is found to make rather different predictions; including apparent conical intersections for certain particles that are not observed with TD-CAM-B3LYP nor with TD-BHLYP. In line with our previous observations for vertical excitations, the issue with TD-B3LYP appears to be the inherent tendency of TD-B3LYP, and other XC potentials with no or a low percentage of Hartree-Fock Like Exchange, to spuriously stabilize the energy of charge-transfer (CT) states. Even in the case of hydrated particles, for which vertical excitations are generally well described with all XC potentials, the use of TD-B3LYP appears to result in CT-problems for certain particles. We hypothesize that the spurious stabilization of CT-states by TD-B3LYP even may drive the excited state optimizations to different excited state geometries than those obtained using TD-CAM-B3LYP or TD-BHLYP. In conclusion, focusing on the TD-CAM-B3LYP and TD-BHLYP results, excited state relaxation in naked and hydrated TiO 2 nanoparticles is predicted to be associated with a large Stokes' shift

Examination of excited state populations in sputtering using Multiphoton Resonance Ionization

International Nuclear Information System (INIS)

Kimock, F.M.; Baxter, J.P.; Pappas, D.L.; Kobrin, P.H.; Winograd, N.

1984-01-01

Multiphoton Resonance Ionization has been employed to study the populations of excited state atoms ejected from ion bombarded metal surfaces. Preliminary investigations have focused on three model systems: aluminum, indium and cobalt. In this paper the authors examine the effect of primary ion energy (2 to 12 keV Ar + ) on excited state yields for these three systems. The influence of the sample matrix on excited state populations of sputtered atoms is also discussed

Structure of excited states in nuclei near doubly magic {sup 100}SN

Energy Technology Data Exchange (ETDEWEB)

Gorska, M.

1998-11-01

The three neutron-deficient nuclei {sup 94}Pd, {sup 98}Cd and {sup 104}Sn in the vicinity of {sup 100}Sn were investigated by means of in-beam {gamma}-ray spectroscopy of excited states. The isomeric decays in {sup 94}Pd and {sup 98}Cd were studied for the first time with an exclusive experimental setup for delayed {gamma}-ray detection with complete exit channel identification based on information from neutron and charged-particle filter detectors. The structure of excited states of {sup 94}Pd showed the first indication of increasing proton-neutron interaction towards the N=Z line in this region of nuclei, that in turn might be related to increased proton-neutron pairing correlations predicted in T{sub z}=0 nuclei. The closest neighbours of {sup 100}Sn with two active particles, {sup 98}Cd and {sup 102}Sn, are now known with their lowest excited states. The measured reduced transition probabilities for the decay of the isomeric 8{sup +} and 6{sup +} states in {sup 98}Cd and {sup 102}Sn, respectively, allowed to extract an effective quadrupole charge for neutron and proton in this region of nuclei based on the high configurational purity of the states. While the neutron effective charge appeared to be large and in agreement with expectation, the proton effective charge value is very small (e{sub {pi}}{<=}1). This controversial result, which would indicate that {sup 100}Sn is a very good closed shell nucleus with respect to quadrupole excitation, is not understood. An experimental reason for this result, related to existence of a core excited isomer, observed in the experiment by means of its half life but not {gamma}-rays, which may have escaped observation, can not be definitely excluded and is left as possible explanation. (orig.)

Dynamics of the excited state intramolecular charge transfer

International Nuclear Information System (INIS)

Joo, T.; Kim, C.H.

2006-01-01

The 6-dodecanoyl-2-dimethylaminonaphtalene (laurdan), a derivative of 6-propanoyl- 2-dimethylaminonaphthalene (prodan), has been used as a fluorescent probe in cell imaging, especially in visualizing the lipid rafts by the generalized polarization (GP) images, where GP=(I 440 -I 490 )/(I 440 +I 490 ) with I being the fluorescence intensity. The fluorescence spectrum of laurdan is sensitive to its dipolar environment due to the intramolecular charge transfer (ICT) process in S 1 state, which results in a dual emission from the locally excited (LE) and the ICT states. The ICT process and the solvation of the ICT state are very sensitive to the dipolar nature of the environment. In this work, the ICT of laurdan in ethanol has been studied by femtosecond time resolved fluorescence (TRF), especially TRF spectra measurement without the conventional spectral reconstruction method. TRF probes the excited states exclusively, a unique advantage over the pump/probe transient absorption technique, although time resolution of the TRF is generally lower than transient absorption and the TRF spectra measurement was possible only though the spectral reconstruction. Over the years, critical advances in TRF technique have been made in our group to achieve <50 fs time resolution with direct full spectra measurement capability. Detailed ICT and the subsequent solvation processes can be visualized unambiguously from the TRF spectra. Fig. 1 shows the TRF spectra of laurdan in ethanol at several time delays. Surprisingly, two bands at 433 and 476 nm are clearly visible in the TRF spectra of laurdan even at T = 0 fs. As time increases, the band at 476 nm shifts to the red while its intensity increases. The band at 433 nm also shifts slightly to the red, but loses intensity as time increases. The intensity of the 476 nm band reaches maximum at around 5 ps, where it is roughly twice as intense as that at 0 fs, and stays constant until lifetime decay is noticeable. The spectra were fit by

Analytical study of doubly excited ridge states

International Nuclear Information System (INIS)

Wong, H.Y.

1988-01-01

Two different non-separable problems are explored and analyzed. Non-perturbative methods need to be used to handle them, as the competing forces involved in these problems are equally strong and do not yield to a perturbative analysis. The first one is the study of doubly excited ridge states of atoms, in which two electrons are comparably excited. An analytical wavefunction for such states is introduced and is used to solve the two-electron Hamiltonian in the pair coordinates called hyperspherical coordinates variationally. The correlation between the electrons is built in analytically into the structure of the wavefunction. Sequences of ridge states out to very high excitation are computed and are organized as Rydberg series converging to the double ionization limit. Numerical results of such states in He and H - are compared with other theoretical calculations where available. The second problem is the analysis of the photodetachment of negative ions in an electric field via the frame transformation theory. The presence of the electron field requires a transformation from spherical to cylindrical symmetry for the outgoing photoelectron. This gives an oscillatory modulating factor as the effect of the electric field on cross-sections. All of this work is derived analytically in a general form applicable to the photodetachment of any negative ion. The expressions are applied to H - and S - for illustration

Dinamical polarizability of highly excited hydrogen-like states

International Nuclear Information System (INIS)

Delone, N.B.; Krajnov, V.P.

1982-01-01

Analytic expressions are derived for the dynamic polarizability of highly excited hydrogen-like atomic states. It is shown that in the composite matrix element which determines the dynamic polarizability there is a strong compensation of the terms as a result of which the resulting magnitude of the dynamic polarizability is quasiclasically small compared to the individual terms of the composite matrix. It is concluded that the resonance behaviour of the dynamic polarizability of highly excited states differs significantly from the resonance behaviour of the polarizability for the ground and low-lying atomic states. The static limit and high-frequency limit of on electromagnetic field are considered

Excitation of non-normal parity states by inelastic proton scattering

Energy Technology Data Exchange (ETDEWEB)

Emery, G. T. [Indiana Univ. (USA). Cyclotron Facility; Ikegami, Hidetsugu; Muraoka, Mitsuo [eds.; Osaka Univ., Suita (Japan). Research Center for Nuclear Physics

1980-01-01

This is a review of the works done at the Indiana University Cyclotron Facility. The purposes of works are to find excitations that should have especially simple particle-hole structure in proton inelastic scattering, to use the data on these excitations to try to understand the mechanism and the effective interaction for the (p, p') reaction in this energy range, and to go on to study the nuclear structure involved in less simple excitation. As an example, the single-nucleon level diagram for the region of Si-28 is presented. A high spin state was made, and its spin-parity was 6/sup -/. It was tried to interpret the data in terms of a on-step distorted-wave impulse approximation. The optical model parameters derived from the extensive and precise elastic scattering results were used. The cross sections for the excitation of the 6/sup -/ states found in various reactions were not large. The T = 1 state is mainly excited by the direct tensor interaction, while the T = 0 state gets its strength mainly from the knock-on exchange contribution of both the tensor and spin-orbit interactions. Experiments on Pb-208 and Fe-54 are being performed.

Examination of excited state populations in sputtering using multiphoton resonance ionization

International Nuclear Information System (INIS)

Kimock, F.M.; Baxter, J.P.; Pappas, D.L.; Kobrin, P.H.; Winograd, N.

1984-01-01

Multiphoton Resonance Ionization has been employed to study the populations of excited state atoms ejected from ion bombarded metal surfaces. Preliminary investigations have focused on three model systems: aluminum, indium and cobalt. In this paper we examine the effect of primary ion energy (2 to 12 keV Ar + ) on excited state yields for these three systems. The influence of the sample matrix on excited state populations of sputtered atoms is also discussed. 8 refs., 4 figs

Singlet versus Triplet Excited State Mediated Photoinduced Dehalogenation Reactions of Itraconazole in Acetonitrile and Aqueous Solutions.

Science.gov (United States)

Zhu, Ruixue; Li, Ming-de; Du, Lili; Phillips, David Lee

2017-04-06

Photoinduced dehalogenation of the antifungal drug itraconazole (ITR) in acetonitrile (ACN) and ACN/water mixed solutions was investigated using femtosecond and nanosecond time-resolved transient absorption (fs-TA and ns-TA, respectively) and nanosecond time-resolved resonance Raman spectroscopy (ns-TR 3 ) experiments. An excited resonance energy transfer is found to take place from the 4-phenyl-4,5-dihydro-3H-1,2,4-triazol-3-one part of the molecule to the 1,3-dichlorobenzene part of the molecule when ITR is excited by ultraviolet light. This photoexcitation is followed by a fast carbon-halogen bond cleavage that leads to the generation of radical intermediates via either triplet and/or singlet excited states. It is found that the singlet excited state-mediated carbon-halogen cleavage is the predominant dehalogenation process in ACN solvent, whereas a triplet state-mediated carbon-halogen cleavage prefers to occur in the ACN/water mixed solutions. The singlet-to-triplet energy gap is decreased in the ACN/water mixed solvents and this helps facilitate an intersystem crossing process, and thus, the carbon-halogen bond cleavage happens mostly through an excited triplet state in the aqueous solutions examined. The ns-TA and ns-TR 3 results also provide some evidence that radical intermediates are generated through a homolytic carbon-halogen bond cleavage via predominantly the singlet excited state pathway in ACN but via mainly the triplet state pathway in the aqueous solutions. In strong acidic solutions, protonation at the oxygen and/or nitrogen atoms of the 1,2,4-triazole-3-one group appears to hinder the dehalogenation reactions. This may offer the possibility that the phototoxicity of ITR due to the generation of aryl or halogen radicals can be reduced by protonation of certain moieties in suitably designed ITR halogen-containing derivatives.

Excited-State Dynamics of Carotenoids Studied by Femtosecond Transient Absorption Spectroscopy

International Nuclear Information System (INIS)

Lee, Ingu; Pang, Yoonsoo; Lee, Sebok

2014-01-01

Carotenoids, natural antenna pigments in photosynthesis share a symmetric backbone of conjugated polyenes. Contrary to the symmetric and almost planar geometries of carotenoids, excited state structure and dynamics of carotenoids are exceedingly complex. In this paper, recent infrared and visible transient absorption measurements and excitation dependent dynamics of 8'-apo-β-caroten-8'-al and 7',7'-dicyano-7'-apo-β-carotene will be reviewed. The recent visible transient absorption measurements of 8'-apo-β-caroten-8'-al in polar and nonpolar solvents will also be introduced to emphasize the complex excited-state dynamics and unsolved problems in the S 2 and S 1 excited states

Cathodoluminescence imaging and spectroscopy of excited states in InAs self-assembled quantum dots

International Nuclear Information System (INIS)

Khatsevich, S.; Rich, D.H.; Kim, Eui-Tae; Madhukar, A.

2005-01-01

We have examined state filling and thermal activation of carriers in buried InAs self-assembled quantum dots (SAQDs) with excitation-dependent cathodoluminescence (CL) imaging and spectroscopy. The InAs SAQDs were formed during molecular-beam epitaxial growth of InAs on undoped planar GaAs (001). The intensities of the ground- and excited-state transitions were analyzed as a function of temperature and excitation density to study the thermal activation and reemission of carriers. The thermal activation energies associated with the thermal quenching of the luminescence were measured for ground- and excited-state transitions of the SAQDs, as a function of excitation density. By comparing these activation energies with the ground- and excited-state transition energies, we have considered various processes that describe the reemission of carriers. Thermal quenching of the intensity of the QD ground- and first excited-state transitions at low excitations in the ∼230-300-K temperature range is attributed to dissociation of excitons from the QD states into the InAs wetting layer. At high excitations, much lower activation energies of the ground and excited states are obtained, suggesting that thermal reemission of single holes from QD states into the GaAs matrix is responsible for the observed temperature dependence of the QD luminescence in the ∼230-300-K temperature range. The dependence of the CL intensity of the ground-and first excited-state transition on excitation density was shown to be linear at all temperatures at low-excitation density. This result can be understood by considering that carriers escape and are recaptured as excitons or correlated electron-hole pairs. At sufficiently high excitations, state-filling and spatial smearing effects are observed together with a sublinear dependence of the CL intensity on excitation. Successive filling of the ground and excited states in adjacent groups of QDs that possess different size distributions is assumed to

Photophysics of trioxatriangulenium ion. Electrophilic reactivity in the ground state and excited singlet state

DEFF Research Database (Denmark)

Reynisson, J.; Wilbrandt, R.; Brinck, V.

2002-01-01

. The physical and chemical properties of the excited singlet state of the trioxatriangulenium (TOTA(+)) carbenium ion are investigated by experimental and Computational means. The degeneracy of the lowest excited states is counteracted by Jahn-Teller-type distortion, which leads to vibronic broadening...... of the long wavelength absorption band. A strong fluorescence is observed at 520 nm (tau(n) = 14.6 ns, phi(n) = 0.12 in deaerated acetonitrile). The fluorescence is quenched by 10 aromatic electron donors predominantly via a dynamic charge transfer mechanism, but ground state complexation is shown...... triphenylenes is studied separately. Phosphorescence spectra, triplet lifetimes, and triplet-triplet absorption spectra are provided. In the discussion, TOTA(+) is compared to the unsubstituted xanthenium ion and its 9-phenyl derivative with respect to the excited state properties....

Decay of hollow states in time-dependent density functional theory

Energy Technology Data Exchange (ETDEWEB)

Kapoor, Varun; Bauer, Dieter [Institut fuer Physik, Wismarsche Str. 43-45, Universitaet Rostock, Rostock-18051 (Germany)

2012-07-01

Hollow or multiply excited states are inaccessible in time dependent density functional theory (TDDFT) using adiabatic Kohn-Sham potentials. We determine the exact Kohn Sham (KS) potential for doubly excited states in an exactly solvable model Helium atom. The exact single-particle density corresponds to the energetically lowest quasi-stationary state in the exact KS potential. We describe how this exact potential controls the decay by a barrier whose origin is traced back to phase of the exact KS orbital. The potential controls the barrier height and width in order for the density to tunnel out and decay with the same rate as the doubly excited state in the ab initio time-dependent Schroedinger calculation. Instead, adiabatic KS potentials only show direct photoionization but no autoionization. A frequency-dependent linear response kernel would be necessary in order to capture the decay of autoionizing states.

DILEPTON YIELD FROM THE DECAY OF EXCITED SI-28 STATES

NARCIS (Netherlands)

BACELAR, JC; BUDA, A; BALANDA, A; KRASZNAHORKAY, A; VANDERPLOEG, H; SUJKOWSKI, Z; VANDERWOUDE, A

1994-01-01

The first dilepton yield measurements from excited nuclear states obtained with a new Positron-Electron Pair Spectroscopic Instrument (PEPSI) are reported. Nuclear states in Si-28, with an initial excitation energy E* = 50 MeV, were populated via the isospin T = 0 reaction He-4 + Mg-24 and the

Many-body excitations and deexcitations in trapped ultracold bosonic clouds

Science.gov (United States)

Theisen, Marcus; Streltsov, Alexej I.

2016-11-01

We employ the multiconfigurational time-dependent Hartree for bosons (MCTDHB) method to study excited states of interacting Bose-Einstein condensates confined by harmonic and double-well trap potentials. Two approaches to access excitations, one static and the other dynamic, are investigated and contrasted. In static simulations the low-lying excitations are computed by utilizing a linear-response theory constructed on top of a static MCTDHB solution (LR-MCTDHB). Complimentarily, we propose two dynamic protocols that address excitations by propagating the MCTDHB wave function. In particular, we investigate dipolelike oscillations induced by shifting the origin of the confining potential and breathinglike excitations by quenching the frequency of a parabolic part of the trap. To contrast static predictions and dynamic results we compute the time evolution and regard the respective Fourier transform of several local and nonlocal observables. Namely, we study the expectation value of the position operator , its variance Var [x (t )] , and a local density computed at selected positions. We find that the variance is the most sensitive and informative quantity: Along with excitations it contains information about deexcitations even in a linear regime of the induced dynamics. The dynamic protocols are found to access the many-body excitations predicted by the static LR-MCTDHB approach.

The Astrophysical Weeds: Rotational Transitions in Excited Vibrational States

Science.gov (United States)

Alonso, José L.; Kolesniková, Lucie; Alonso, Elena R.; Mata, Santiago

2017-06-01

The number of unidentified lines in the millimeter and submillimeter wave surveys of the interstellar medium has grown rapidly. The major contributions are due to rotational transitions in excited vibrational states of a relatively few molecules that are called the astrophysical weeds. necessary data to deal with spectral lines from astrophysical weeds species can be obtained from detailed laboratory rotational measurements in the microwave and millimeter wave region. A general procedure is being used at Valladolid combining different time and/or frequency domain spectroscopic tools of varying importance for providing the precise set of spectroscopic constants that could be used to search for this species in the ISM. This is illustrated in the present contribution through its application to several significant examples. Fortman, S. M., Medvedev, I. R., Neese, C.F., & De Lucia, F.C. 2010, ApJ,725, 1682 Rotational Spectra in 29 Vibrationally Excited States of Interstellar Aminoacetonitrile, L. Kolesniková, E. R. Alonso, S. Mata, and J. L. Alonso, The Astrophysical Journal Supplement Series 2017, (in press).

Thermality and excited state Rényi entropy in two-dimensional CFT

Energy Technology Data Exchange (ETDEWEB)

Lin, Feng-Li [Department of Physics, National Taiwan Normal University,Taipei 11677, Taiwan (China); Wang, Huajia [Department of Physics, University of Illinois,Urbana-Champaign, IL 61801 (United States); Zhang, Jia-ju [Dipartimento di Fisica, Università degli Studi di Milano-Bicocca,Piazza della Scienza 3, I-20126 Milano (Italy); Theoretical Physics Division, Institute of High Energy Physics, Chinese Academy of Sciences,19B Yuquan Rd, Beijing 100049 (China); Theoretical Physics Center for Science Facilities, Chinese Academy of Sciences,19B Yuquan Rd, Beijing 100049 (China)

2016-11-21

We evaluate one-interval Rényi entropy and entanglement entropy for the excited states of two-dimensional conformal field theory (CFT) on a cylinder, and examine their differences from the ones for the thermal state. We assume the interval to be short so that we can use operator product expansion (OPE) of twist operators to calculate Rényi entropy in terms of sum of one-point functions of OPE blocks. We find that the entanglement entropy for highly excited state and thermal state behave the same way after appropriate identification of the conformal weight of the state with the temperature. However, there exists no such universal identification for the Rényi entropy in the short-interval expansion. Therefore, the highly excited state does not look thermal when comparing its Rényi entropy to the thermal state one. As the Rényi entropy captures the higher moments of the reduced density matrix but the entanglement entropy only the average, our results imply that the emergence of thermality depends on how refined we look into the entanglement structure of the underlying pure excited state.

Interference between radiative emission and autoionization in the decay of excited states of atoms

International Nuclear Information System (INIS)

Armstrong, L. Jr.; Theodosiou, C.E.; Wall, M.J.

1978-01-01

An excited state of an atom which can autoionize can also undergo radiative decay. We consider the interaction between the final states resulting from these two modes of decay, and its effects on such quantities as the fluorescence yield of the excited state, excitation profile of the excited state, and the spectra of the emitted photons and electrons. It is shown that the fraction of decays of the excited state resulting in a photon (fluorescence yield) is particularly sensitive to the details of the final-state interaction. In lowest order in the final-state interaction, the fluorescence yield is increased by a factor (1 + 1/q 2 ) from the traditional value, where q is the Fano q parameter relating to the excited state and the final atomic state

The influence of autoionizing states on the excitation of helium by electrons

International Nuclear Information System (INIS)

Ittersum, T. van

1976-01-01

The work described in this thesis deals with resonance effects in the scattering of electrons by helium at energies near the threshold of the autoionizing states (50-70 eV). The investigation is performed by studying light emission following the excitation of singly excited states. In some cases, the polarization of the radiation was also investigated. The purpose of the research was (i) to enlarge our knowledge of triply excited negative ion states, i.e. resonance states which are formed by temporary binding of the incident electron to a doubly excited (autoionizing) state of neutral helium, and (ii) to clear up the nature of some resonance structures which could not be explained in terms of negative ion resonances

Excited-State Dynamics of Carotenoids Studied by Femtosecond Transient Absorption Spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Lee, Ingu; Pang, Yoonsoo [Department of Physics and Photon Science, Gwangju (Korea, Republic of); Lee, Sebok [Gwangju Institute of Science and Technology, Gwangju (Korea, Republic of)

2014-03-15

Carotenoids, natural antenna pigments in photosynthesis share a symmetric backbone of conjugated polyenes. Contrary to the symmetric and almost planar geometries of carotenoids, excited state structure and dynamics of carotenoids are exceedingly complex. In this paper, recent infrared and visible transient absorption measurements and excitation dependent dynamics of 8'-apo-β-caroten-8'-al and 7',7'-dicyano-7'-apo-β-carotene will be reviewed. The recent visible transient absorption measurements of 8'-apo-β-caroten-8'-al in polar and nonpolar solvents will also be introduced to emphasize the complex excited-state dynamics and unsolved problems in the S{sub 2} and S{sub 1} excited states.

Excited state dynamics of beta-carotene explored with dispersed multi-pulse transient absorption

NARCIS (Netherlands)

Larsen, D.S.; Papagiannakis, E.; van Stokkum, I.H.M.; Vengris, M.; Kennis, J.T.M.; van Grondelle, R.

2003-01-01

The excited-state dynamics of β-carotene in hexane was studied with dispersed ultrafast transient absorption techniques. A new excited state is produced after blue-edge excitation. Pump-repump-probe and pump-dump-probe measurements identified and characterized this state, termed S‡, which exhibits a

Time-dependent weak values and their intrinsic phases of evolution

International Nuclear Information System (INIS)

Parks, A D

2008-01-01

The equation of motion for a time-dependent weak value of a quantum-mechanical observable is known to contain a complex valued energy factor (the weak energy of evolution) that is defined by the dynamics of the pre-selected and post-selected states which specify the observable's weak value. In this paper, the mechanism responsible for the creation of this energy is identified and it is shown that the cumulative effect over time of this energy is manifested as dynamical phases and pure geometric phases (the intrinsic phases of evolution) which govern the evolution of the weak value during its measurement process. These phases are simply related to a Pancharatnam phase and Fubini-Study metric distance defined by the Hilbert space evolution of the associated pre-selected and post-selected states. A characterization of time-dependent weak value evolution as Pancharatnam phase angle rotations and Fubini-Study distance scalings of a vector in the Argand plane is discussed as an application of this relationship. The theory of weak values is also reviewed and simple 'gedanken experiments' are used to illustrate both the time-independent and the time-dependent versions of the theory. It is noted that the direct experimental observation of the weak energy of evolution would strongly support the time-symmetric paradigm of quantum mechanics and it is suggested that weak value equations of motion represent a new category of nonlocal equations of motion

Excited-state lifetime measurement of silicon vacancy centers in diamond by single-photon frequency upconversion

Science.gov (United States)

Rong, Youying; Ma, Jianhui; Chen, Lingxiao; Liu, Yan; Siyushev, Petr; Wu, Botao; Pan, Haifeng; Jelezko, Fedor; Wu, E.; Zeng, Heping

2018-05-01

We report a method with high time resolution to measure the excited-state lifetime of silicon vacancy centers in bulk diamond avoiding timing jitter from the single-photon detectors. Frequency upconversion of the fluorescence emitted from silicon vacancy centers was achieved from 738 nm to 436 nm via sum frequency generation with a short pump pulse. The excited-state lifetime can be obtained by measuring the intensity of upconverted light while the pump delay changes. As a probe, a pump laser with pulse duration of 11 ps provided a high temporal resolution of the measurement. The lifetime extracted from the pump–probe curve was 0.755 ns, which was comparable to the timing jitter of the single-photon detectors.

Dielectronic recombination rate coefficients to the excited states of CI from CII

International Nuclear Information System (INIS)

Dubau, J.; Kato, T.; Safronova, U.I.

1998-01-01

The dielectronic recombination rate coefficients to the excited states for n=2-6 are calculated including 1s 2 2l 1 2l 2 2l 3 nl (n=2-6, l≤(n-1)) states. The values for the excited states higher than n=6 are extrapolated and the total dielectronic recombination rate coefficients are derived. The rate coefficients to the excited states are fitted to an analytical formula and the fit parameters are given. (author)

Excited-state dynamics of acetylene excited to individual rotational level of the V04K01 subband

Science.gov (United States)

Makarov, Vladimir I.; Kochubei, Sergei A.; Khmelinskii, Igor V.

2006-01-01

Dynamics of the IR emission induced by excitation of the acetylene molecule using the (32Ka0,1,2,ÃAu1←41la1,X˜Σg+1) transition was investigated. The observed IR emission was assigned to transitions between the ground-state vibrational levels. Acetylene fluorescence quenching induced by external electric and magnetic fields acting upon the system prepared using the (34Ka1,ÃAu1←00la0,X˜Σg+1) excitation was also studied. External electric field creates an additional radiationless pathway to the ground-state levels, coupling levels of the ÃAu1 excited state to the quasiresonant levels of the X˜Σg+1 ground state. The level density of the ground state in the vicinity of the excited state is very high, thus the electric-field-induced transition is irreversible, with the rate constant described by the Fermi rule. Magnetic field alters the decay profile without changing the fluorescence quantum yield in collisionless conditions. IR emission from the CCH transient was detected, and was also affected by the external electric and magnetic fields. Acetylene predissociation was demonstrated to proceed by the direct S1→S0 mechanism. The results were explained using the previously developed theoretical approach, yielding values of the relevant model parameters.

Excited state properties of aryl carotenoids

Czech Academy of Sciences Publication Activity Database

Fuciman, M.; Chábera, P.; Župčanová, Anita; Hříbek, P.; Arellano, J.B.; Vácha, František; Pšenčík, J.; Polívka, Tomáš

2010-01-01

Roč. 12, č. 13 (2010), s. 3112-3120 ISSN 1463-9076 R&D Projects: GA AV ČR IAA608170604 Institutional research plan: CEZ:AV0Z50510513 Keywords : carotenoids * excited-states * femtosecond spectroscopy Subject RIV: BO - Biophysics Impact factor: 3.454, year: 2010

Spectroscopic properties of the S1 state of linear carotenoids after excess energy excitation

Science.gov (United States)

Kuznetsova, Valentyna; Southall, June; Cogdell, Richard J.; Fuciman, Marcel; Polívka, Tomáš

2017-09-01

Properties of the S1 state of neurosporene, spheroidene and lycopene were studied after excess energy excitation in the S2 state. Excitation of carotenoids into higher vibronic levels of the S2 state generates excess vibrational energy in the S1 state. The vibrationally hot S1 state relaxes faster when carotenoid is excited into the S2 state with excess energy, but the S1 lifetime remains constant regardless of which vibronic level of the S2 state is excited. The S∗ signal depends on excitation energy only for spheroidene, which is likely due to asymmetry of the molecule, facilitating conformations responsible for the S∗ signal.

Formation and role of excited states in radiolysis - a foreword

International Nuclear Information System (INIS)

Singh, A.

1976-01-01

It is stated that the choice of contributions to the special issue of this Journal has been limited to those which bear on the details of the mechanisms of excited state formation and are likely to be useful to radiation chemists. Since more than half the energy deposited in radiolysis goes into excitation, studies on the fate of the excited species formed are very important. A brief reference is made to the subject matter of each of the fifteen contributions, and its significance to the development of the technique of radiolysis is outlined. (U.K.)

Dynamics of electron solvation in methanol: Excited state relaxation and generation by charge-transfer-to-solvent

International Nuclear Information System (INIS)

Elkins, Madeline H.; Williams, Holly L.; Neumark, Daniel M.

2015-01-01

The charge-transfer-to-solvent dynamics (CTTS) and excited state relaxation mechanism of the solvated electron in methanol are studied by time-resolved photoelectron spectroscopy on a liquid methanol microjet by means of two-pulse and three-pulse experiments. In the two-pulse experiment, CTTS excitation is followed by a probe photoejection pulse. The resulting time-evolving photoelectron spectrum reveals multiple time scales characteristic of relaxation and geminate recombination of the initially generated electron which are consistent with prior results from transient absorption. In the three-pulse experiment, the relaxation dynamics of the solvated electron following electronic excitation are measured. The internal conversion lifetime of the excited electron is found to be 130 ± 40 fs, in agreement with extrapolated results from clusters and the non-adiabatic relaxation mechanism

Dynamics of electron solvation in methanol: Excited state relaxation and generation by charge-transfer-to-solvent

Science.gov (United States)

Elkins, Madeline H.; Williams, Holly L.; Neumark, Daniel M.

2015-06-01

The charge-transfer-to-solvent dynamics (CTTS) and excited state relaxation mechanism of the solvated electron in methanol are studied by time-resolved photoelectron spectroscopy on a liquid methanol microjet by means of two-pulse and three-pulse experiments. In the two-pulse experiment, CTTS excitation is followed by a probe photoejection pulse. The resulting time-evolving photoelectron spectrum reveals multiple time scales characteristic of relaxation and geminate recombination of the initially generated electron which are consistent with prior results from transient absorption. In the three-pulse experiment, the relaxation dynamics of the solvated electron following electronic excitation are measured. The internal conversion lifetime of the excited electron is found to be 130 ± 40 fs, in agreement with extrapolated results from clusters and the non-adiabatic relaxation mechanism.

Dynamics of electron solvation in methanol: Excited state relaxation and generation by charge-transfer-to-solvent

Energy Technology Data Exchange (ETDEWEB)

Elkins, Madeline H.; Williams, Holly L. [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Neumark, Daniel M. [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2015-06-21

The charge-transfer-to-solvent dynamics (CTTS) and excited state relaxation mechanism of the solvated electron in methanol are studied by time-resolved photoelectron spectroscopy on a liquid methanol microjet by means of two-pulse and three-pulse experiments. In the two-pulse experiment, CTTS excitation is followed by a probe photoejection pulse. The resulting time-evolving photoelectron spectrum reveals multiple time scales characteristic of relaxation and geminate recombination of the initially generated electron which are consistent with prior results from transient absorption. In the three-pulse experiment, the relaxation dynamics of the solvated electron following electronic excitation are measured. The internal conversion lifetime of the excited electron is found to be 130 ± 40 fs, in agreement with extrapolated results from clusters and the non-adiabatic relaxation mechanism.

UV excitation of single DNA and RNA strands produces high yields of exciplex states between two stacked bases.

Science.gov (United States)

Takaya, Tomohisa; Su, Charlene; de La Harpe, Kimberly; Crespo-Hernández, Carlos E; Kohler, Bern

2008-07-29

Excited electronic states created by UV excitation of the diribonucleoside monophosphates ApA, ApG, ApC, ApU, and CpG were studied by the femtosecond transient-absorption technique. Bleach recovery signals recorded at 252 nm show that long-lived excited states are formed in all five dinucleosides. The lifetimes of these states exceed those measured in equimolar mixtures of the constituent mononucleotides by one to two orders of magnitude, indicating that electronic coupling between proximal nucleobases dramatically slows the relaxation of excess electronic energy. The decay rates of the long-lived states decrease with increasing energy of the charge-transfer state produced by transferring an electron from one base to another. The charge-transfer character of the long-lived states revealed by this analysis supports their assignment to excimer or exciplex states. Identical bleach recovery signals were seen for ApA, (A)(4), and poly(A) at delay times >10 ps after photoexcitation. This indicates that excited states localized on a stack of just two bases are the common trap states independent of the number of stacked nucleotides. The fraction of initial excitations that decay to long-lived exciplex states is approximately equal to the fraction of stacked bases determined by NMR measurements. This supports a model in which excitations associated with two stacked bases decay to exciplex states, whereas excitations in unstacked bases decay via ultrafast internal conversion. These results establish the importance of charge transfer-quenching pathways for UV-irradiated RNA and DNA in room-temperature solution.

Local density approximation for exchange in excited-state density functional theory

OpenAIRE

Harbola, Manoj K.; Samal, Prasanjit

2004-01-01

Local density approximation for the exchange energy is made for treatment of excited-states in density-functional theory. It is shown that taking care of the state-dependence of the LDA exchange energy functional leads to accurate excitation energies.

Dielectronic recombination rate coefficients to the excited states of CI from CII

Energy Technology Data Exchange (ETDEWEB)

Dubau, J. [Observatoire of Paris, 92 MEUDON (France); Kato, T.; Safronova, U.I.

1998-01-01

The dielectronic recombination rate coefficients to the excited states for n=2-6 are calculated including 1s{sup 2}2l{sub 1}2l{sub 2}2l{sub 3}nl (n=2-6, l{<=}(n-1)) states. The values for the excited states higher than n=6 are extrapolated and the total dielectronic recombination rate coefficients are derived. The rate coefficients to the excited states are fitted to an analytical formula and the fit parameters are given. (author)

Visible-Light-Mediated Excited State Relaxation in Semi-Synthetic Genetic Alphabet: d5SICS and dNaM.

Science.gov (United States)

Bhattacharyya, Kalishankar; Datta, Ayan

2017-08-25

The excited state dynamics of an unnatural base pair (UBP) d5SICS/dNaM were investigated by accurate ab-initio calculations. Time-dependent density functional and high-level multireference calculations (MS-CASPT2) were performed to elucidate the excitation of this UBP and its excited state relaxation mechanism. After excitation to the bright state S 2 (ππ*), it decays to the S 1 state and then undergoes efficient intersystem crossing to the triplet manifold. The presence of sulfur atom in d5SICS leads to strong spin-orbit coupling (SOC) and a small energy gap that facilitates intersystem crossing from S 1 (n s π*) to T 2 (ππ*) followed by internal conversion to T 1 state. Similarly in dNaM, the deactivation pathway follows analogous trends. CASPT2 calculations suggest that the S 1 (ππ*) state is a dark state below the accessible S 2 (ππ*) bright state. During the ultrafast deactivation, it exhibits bond length inversion. From S 1 state, significant SOC leads the population transfer to T 3 due to a smaller energy gap. Henceforth, fast internal conversion occurs from T 3 to T 2 followed by T 1 . From time-dependent trajectory surface hopping dynamics, it is found that excited state relaxation occurs on a sub-picosecond timescale in d5SICS and dNaM. Our findings strongly suggest that there is enough energy available in triplet state of UBP to generate reactive oxygen species and induce phototoxicity with respect to cellular DNA. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Excited-state Raman spectroscopy with and without actinic excitation: S1 Raman spectra of trans-azobenzene

International Nuclear Information System (INIS)

Dobryakov, A. L.; Quick, M.; Ioffe, I. N.; Granovsky, A. A.; Ernsting, N. P.; Kovalenko, S. A.

2014-01-01

We show that femtosecond stimulated Raman spectroscopy can record excited-state spectra in the absence of actinic excitation, if the Raman pump is in resonance with an electronic transition. The approach is illustrated by recording S 1 and S 0 spectra of trans-azobenzene in n-hexane. The S 1 spectra were also measured conventionally, upon nπ* (S 0 → S 1 ) actinic excitation. The results are discussed and compared to earlier reports

Molecular excited states from the SCAN functional

Science.gov (United States)

Tozer, David J.; Peach, Michael J. G.

2018-06-01

The performance of the strongly constrained and appropriately normed (SCAN) meta-generalised gradient approximation exchange-correlation functional is investigated for the calculation of time-dependent density-functional theory molecular excitation energies of local, charge-transfer and Rydberg character, together with the excited ? potential energy curve in H2. The SCAN results frequently resemble those obtained using a global hybrid functional, with either a standard or increased fraction of exact orbital exchange. For local excitations, SCAN can exhibit significant triplet instability problems, resulting in imaginary triplet excitation energies for a number of cases. The Tamm-Dancoff approximation offers a simple approach to improve the situation, but the excitation energies are still significantly underestimated. Understanding the origin of these (near)-triplet instabilities may provide useful insight into future functional development.

A ballistic transport model for electronic excitation following particle impact

Science.gov (United States)

Hanke, S.; Heuser, C.; Weidtmann, B.; Wucher, A.

2018-01-01

We present a ballistic model for the transport of electronic excitation energy induced by keV particle bombardment onto a solid surface. Starting from a free electron gas model, the Boltzmann transport equation (BTE) is employed to follow the evolution of the temporal and spatial distribution function f (r → , k → , t) describing the occupation probability of an electronic state k → at position r → and time t. Three different initializations of the distribution function are considered: i) a thermal distribution function with a locally and temporally elevated electron temperature, ii) a peak excitation at a specific energy above the Fermi level with a quasi-isotropic distribution in k-space and iii) an anisotropic peak excitation with k-vectors oriented in a specific transport direction. While the first initialization resembles a distribution function which may, for instance, result from electronic friction of moving atoms within an ion induced collision cascade, the peak excitation can in principle result from an autoionization process after excitation in close binary collisions. By numerically solving the BTE, we study the electronic energy exchange along a one dimensional transport direction to obtain a time and space resolved excitation energy distribution function, which is then analyzed in view of general transport characteristics of the chosen model system.

Photophysics of Curcumin excited state in toluene-polar solvent mixtures: Role of H-bonding properties of the polar solvent

Energy Technology Data Exchange (ETDEWEB)

Saini, R.K.; Das, K., E-mail: kaustuv@rrcat.gov.in

2014-01-15

Excited state dynamics of Curcumin in binary solvent mixtures of toluene and polar H-bonding solvents were compared by using an instrument endowed with 40 ps time resolution. The solvation time constant of Curcumin increases significantly (and can therefore be measured) in polar solvents which have, either, both H-bond donating and accepting ability, or, only H-bond donating ability. These results suggest that the rate limiting step in the excited state dynamics of the pigment might be the formation and reorganization of the intermolecular H-bonding between the keto group of the pigment and the H-bond donating moieties of the polar solvent. -- Highlights: • Excited state dynamics of Curcumin in a binary solvent mixture of toluene and three polar H-bonding solvents were compared. • The solvation time constant increases significantly with polar solvents having, H-bond donating and accepting, or, H-bond donating ability. • Observed results suggest that H-bonding property of polar solvent plays an important role in the excited state dynamics. • Intermolecular H-bonding between the keto group of the pigment and polar solvent may be the rate limiting step.

Photophysics of Curcumin excited state in toluene-polar solvent mixtures: Role of H-bonding properties of the polar solvent

International Nuclear Information System (INIS)

Saini, R.K.; Das, K.

2014-01-01

Excited state dynamics of Curcumin in binary solvent mixtures of toluene and polar H-bonding solvents were compared by using an instrument endowed with 40 ps time resolution. The solvation time constant of Curcumin increases significantly (and can therefore be measured) in polar solvents which have, either, both H-bond donating and accepting ability, or, only H-bond donating ability. These results suggest that the rate limiting step in the excited state dynamics of the pigment might be the formation and reorganization of the intermolecular H-bonding between the keto group of the pigment and the H-bond donating moieties of the polar solvent. -- Highlights: • Excited state dynamics of Curcumin in a binary solvent mixture of toluene and three polar H-bonding solvents were compared. • The solvation time constant increases significantly with polar solvents having, H-bond donating and accepting, or, H-bond donating ability. • Observed results suggest that H-bonding property of polar solvent plays an important role in the excited state dynamics. • Intermolecular H-bonding between the keto group of the pigment and polar solvent may be the rate limiting step

Cluster expansion of the wavefunction. Calculation of electron correlations in ground and excited states by SAC and SAC CI theories

International Nuclear Information System (INIS)

Nakatsuji, H.

1979-01-01

The SAC and SAC CI theories are formulated for actual calculations of singlet ground states and their excited states of arbitrary spin multiplicity. Approximations are considered for the variational methods since time-consuming terms are involved. The results of test calculations for singlet states have shown, with much smaller numbers of variables (sizes of the matrices involved), excellent agreement with the full CI and close-to-full CI results. This shows the utility of the SAC theory for ground states and especially of the SAC CI theory for excited states, since the slow convergence of the CI theory is much more critical for excited states than for ground states. (Auth.)

Probing shape coexistence in neutron-deficient $^{72}$Se via low-energy Coulomb excitation

CERN Multimedia

We propose to study the evolution of nuclear structure in neutron-­deficient $^{72}$Se by performing a low-­energy Coulomb excitation measurement. Matrix elements will be determined for low-­lying excited states allowing for a full comparison with theoretical predictions. Furthermore, the intrinsic shape of the ground state, and the second 0$^{+}$ state, will be investigated using the quadrupole sum rules method.

Photoluminescence and excited state structure in Bi3+-doped Y2SiO5 single crystalline films

International Nuclear Information System (INIS)

Babin, V.; Gorbenko, V.; Krasnikov, A.; Mihokova, E.; Nikl, M.; Zazubovich, S.; Zorenko, Yu.

2013-01-01

Single crystalline films of Bi-doped Y 2 SiO 5 are studied at 4.2–350 K by the time-resolved luminescence methods under excitation in the 3.8–6.2 eV energy range. Ultraviolet luminescence of Y 2 SiO 5 :Bi (≈3.6 eV) is shown to arise from the radiative decay of the metastable and radiative minima of the triplet relaxed excited state (RES) of Bi 3+ centers which are related to the 3 P 0 and 3 P 1 levels of a free Bi 3+ ion, respectively. The lowest-energy excitation band of this emission, located at ≈4.5 eV, is assigned to the 1 S 0 → 3 P 1 transitions of a free Bi 3+ ion. The phenomenological model is proposed to describe the excited-state dynamics of Bi 3+ centers in Y 2 SiO 5 :Bi, and parameters of the triplet RES are determined. -- Highlights: •Luminescence of Y 2 SiO 5 :Bi is investigated for the first time. •Ultraviolet emission arises from Bi 3+ ions located in Y lattice sites. •The triplet relaxed excited states parameters of Bi 3+ centers are determined

Microscopic description and excitation of unitary analog states

Energy Technology Data Exchange (ETDEWEB)

Kisslinger, L S [Carnegie-Mellon Univ., Pittsburgh, Pa. (USA); Van Giai, N [Paris-11 Univ., 91 - Orsay (France). Inst. de Physique Nucleaire

1977-12-05

A microscopic investigation in a self-consistent particle-hole model reveals approximate unitary analog states in spite of large symmetry breaking. The K-nucleus elastic scattering and (K/sup -/, ..pi../sup -/) excitation of these states are studied, showing strong surface effects.

First 3- excited state of 56Fe

International Nuclear Information System (INIS)

Fotiades, N.; Nelson, R. O.; Devlin, M.

2010-01-01

There is no reliable evidence for the existence of the 3.076 MeV (3 - ) level adopted in the ENSDF evaluation for 56 Fe although it has been reported in a few experiments. Previous reports of the observation of this level appear to be based on an incorrect assignment in early (e,e ' ) work. Recent neutron inelastic scattering measurements by Demidov et al. [Phys. At. Nucl. 67, 1884, (2004)] show that the assigned γ-ray decay of this state does not occur at a level consistent with known properties of inelastic scattering. In the present work the 56 Fe(n,n ' γ) reaction was used to populate excited states in 56 Fe. Neutrons in the energy range from 1 to 250 MeV were provided by the pulsed neutron source of the Los Alamos Neutron Science Center's WNR facility. Deexciting γ rays were detected with the GEANIE spectrometer, a Compton suppressed array of 26 Ge detectors. The γ-γ data obtained with GEANIE were used to establish coincidence relations between transitions. All previously reported levels up to E x =3.6 MeV excitation energy were observed except for the 3.076 MeV (3 - ) level. The 991- and 2229-keV transitions, previously reported to deexcite this level, were not observed in the γ-γ coincidence data obtained in the present experiment. The present work supports the assignment of the 4509.6 keV level as the first 3 - excited state in 56 Fe by observation of two previously known transitions deexciting this state.

Natural excitation orbitals from linear response theories : Time-dependent density functional theory, time-dependent Hartree-Fock, and time-dependent natural orbital functional theory

NARCIS (Netherlands)

Van Meer, R.; Gritsenko, O. V.; Baerends, E. J.

2017-01-01

Straightforward interpretation of excitations is possible if they can be described as simple single orbital-to-orbital (or double, etc.) transitions. In linear response time-dependent density functional theory (LR-TDDFT), the (ground state) Kohn-Sham orbitals prove to be such an orbital basis. In

Excited State Structural Dynamics of Carotenoids and ChargeTransfer Systems

Energy Technology Data Exchange (ETDEWEB)

Van Tassle, Aaron Justin [Univ. of California, Berkeley, CA (United States)

2006-01-01

This dissertation describes the development andimplementation of a visible/near infrared pump/mid-infrared probeapparatus. Chapter 1 describes the background and motivation ofinvestigating optically induced structural dynamics, paying specificattention to solvation and the excitation selection rules of highlysymmetric molecules such as carotenoids. Chapter 2 describes thedevelopment and construction of the experimental apparatus usedthroughout the remainder of this dissertation. Chapter 3 will discuss theinvestigation of DCM, a laser dye with a fluorescence signal resultingfrom a charge transfer state. By studying the dynamics of DCM and of itsmethyl deuterated isotopomer (an otherwise identical molecule), we areable to investigate the origins of the charge transfer state and provideevidence that it is of the controversial twisted intramolecular (TICT)type. Chapter 4 introduces the use of two-photon excitation to the S1state, combined with one-photon excitation to the S2 state of thecarotenoid beta-apo-8'-carotenal. These 2 investigations show evidencefor the formation of solitons, previously unobserved in molecular systemsand found only in conducting polymers Chapter 5 presents an investigationof the excited state dynamics of peridinin, the carotenoid responsiblefor the light harvesting of dinoflagellates. This investigation allowsfor a more detailed understanding of the importance of structuraldynamics of carotenoids in light harvesting.

Monte Carlo wave-packet approach to trace nuclear dynamics in molecular excited states by XUV-pump-IR-probe spectroscopy

Science.gov (United States)

Jing, Qingli; Bello, Roger Y.; Martín, Fernando; Palacios, Alicia; Madsen, Lars Bojer

2018-04-01

Recent research interests have been raised in uncovering and controlling ultrafast dynamics in excited neutral molecules. In this work we generalize the Monte Carlo wave packet (MCWP) approach to XUV-pump-IR-probe schemes to simulate the process of dissociative double ionization of H2 where singly excited states in H2 are involved. The XUV pulse is chosen to resonantly excite the initial ground state of H2 to the lowest excited electronic state of 1Σu + symmetry in H2 within the Franck-Condon region. The delayed intense IR pulse couples the excited states of 1Σu + symmetry with the nearby excited states of 1Σg + symmetry. It also induces the first ionization from H2 to H2 + and the second ionization from H2 + to H++H+. To reduce the computational costs in the MCWP approach, a sampling method is proposed to determine in time the dominant ionization events from H2 to H2+. By conducting a trajectory analysis, which is a unique possibility within the MCWP approach, the origins of the characteristic features in the nuclear kinetic energy release spectra are identified for delays ranging from 0 to 140 fs and the nuclear dynamics in the singly excited states in H2 is mapped out.

Embedding potentials for excited states of embedded species

International Nuclear Information System (INIS)

Wesolowski, Tomasz A.

2014-01-01

Frozen-Density-Embedding Theory (FDET) is a formalism to obtain the upper bound of the ground-state energy of the total system and the corresponding embedded wavefunction by means of Euler-Lagrange equations [T. A. Wesolowski, Phys. Rev. A 77(1), 012504 (2008)]. FDET provides the expression for the embedding potential as a functional of the electron density of the embedded species, electron density of the environment, and the field generated by other charges in the environment. Under certain conditions, FDET leads to the exact ground-state energy and density of the whole system. Following Perdew-Levy theorem on stationary states of the ground-state energy functional, the other-than-ground-state stationary states of the FDET energy functional correspond to excited states. In the present work, we analyze such use of other-than-ground-state embedded wavefunctions obtained in practical calculations, i.e., when the FDET embedding potential is approximated. Three computational approaches based on FDET, that assure self-consistent excitation energy and embedded wavefunction dealing with the issue of orthogonality of embedded wavefunctions for different states in a different manner, are proposed and discussed

Shell evolution of stable N = 50-56 Zr and Mo nuclei with respect to low-lying octupole excitations

Energy Technology Data Exchange (ETDEWEB)

Gregor, E.T.; Scheck, M.; Chapman, R.; Gaffney, L.P.; Keatings, J.; Mashtakov, K.R.; O' Donnell, D.; Smith, J.F.; Spagnoletti, P.; Wiseman, C. [University of the West of Scotland, School of Engineering and Computing, Paisley (United Kingdom); SUPA, Scottish Universities Physics Alliance, Glasgow (United Kingdom); Thuerauf, M.; Werner, V. [Technische Universitaet Darmstadt, Institut fuer Kernphysik, Darmstadt (Germany)

2017-03-15

For the N = 50-56 zirconium (Z = 40) and molybdenum (Z = 42) isotopes, the evolution of subshells is evaluated by extracting the effective single-particle energies from available particle-transfer data. The extracted systematic evolution of neutron subshells and the systematics of the excitation energy of the octupole phonons provide evidence for type-II shape coexistence in the Zr isotopes. Employing a simplistic approach, the relative effective single-particle energies are used to estimate whether the formation of low-lying octupole-isovector excitations is possible at the proposed energies. The results raise doubts about this assignment. (orig.)

Holonomic Quantum Control by Coherent Optical Excitation in Diamond

Energy Technology Data Exchange (ETDEWEB)

Zhou, Brian B.; Jerger, Paul C.; Shkolnikov, V. O.; Heremans, F. Joseph; Burkard, Guido; Awschalom, David D.

2017-10-01

Although geometric phases in quantum evolution are historically overlooked, their active control now stimulates strategies for constructing robust quantum technologies. Here, we demonstrate arbitrary singlequbit holonomic gates from a single cycle of nonadiabatic evolution, eliminating the need to concatenate two separate cycles. Our method varies the amplitude, phase, and detuning of a two-tone optical field to control the non-Abelian geometric phase acquired by a nitrogen-vacancy center in diamond over a coherent excitation cycle. We demonstrate the enhanced robustness of detuned gates to excited-state decoherence and provide insights for optimizing fast holonomic control in dissipative quantum systems.

Holonomic Quantum Control by Coherent Optical Excitation in Diamond.

Science.gov (United States)

Zhou, Brian B; Jerger, Paul C; Shkolnikov, V O; Heremans, F Joseph; Burkard, Guido; Awschalom, David D

2017-10-06

Although geometric phases in quantum evolution are historically overlooked, their active control now stimulates strategies for constructing robust quantum technologies. Here, we demonstrate arbitrary single-qubit holonomic gates from a single cycle of nonadiabatic evolution, eliminating the need to concatenate two separate cycles. Our method varies the amplitude, phase, and detuning of a two-tone optical field to control the non-Abelian geometric phase acquired by a nitrogen-vacancy center in diamond over a coherent excitation cycle. We demonstrate the enhanced robustness of detuned gates to excited-state decoherence and provide insights for optimizing fast holonomic control in dissipative quantum systems.

Selective excitation of atoms or molecules to high-lying states

International Nuclear Information System (INIS)

Ducas, T.W.

1978-01-01

This specification relates to the selective excitation of atoms or molecules to high lying states and a method of separating different isotopes of the same element by selective excitation of the isotopes. (U.K.)

Experimental investigation of particle-hole excitations in 91Nb

International Nuclear Information System (INIS)

Singh, Purnima; Palit, R.; Choudhury, D.

2014-01-01

Investigation of high-spin states in nuclei near N = 50 shell closure have attracted considerable attention in recent years. These nuclei provide a suitable laboratory for testing the residual interactions of the spherical shell model. Studies of N = 50, Z ∼ 40 nuclei, revealed that the low-lying states in these nuclei arise from proton excitations within the f 5/2 , p 3/2 , p 1/2 , and g 9/2 orbits. The higher angular momentum states were observed to have dominant contribution of 1p - 1h configurations involving a single g 9/2 neutron excitation across the N = 50 shell gap into the d 5/2 orbit. A comprehensive study of multiparticle-multihole (mp-mh) excitations in these nuclei may provide necessary insight into the evolution of shell structure above N = 50 shell gap. However, till date there is no experimental evidence of states involving two or more neutron excitations across the N = 50 shell gap in N = 50, Z ∼ 40 nuclei. The present work investigates high-spin states in the N = 50 nucleus, 91 Nb, with the purpose to search for states involving 2p - 2h excitations across the N = 50 shell closure

Does the excited state of the 3He nucleus exist?

International Nuclear Information System (INIS)

Barabanov, A.L.

1994-01-01

The suggestion is made that the excited state of the 3 He nucleus found out recently in the reaction has spin and parity 1/2 + and the same configuration that the ground open of 6 He. It is shown that in an elastic nd-scattering a resonance associated with the excited state may be absent due to destructive interference of potential and resonant scattering phases

Supersymmetric quantum mechanics and higher excited states of a non-polynomial potential

International Nuclear Information System (INIS)

Drigo Filho, E.; Ricotta, R.M.

1989-03-01

Supersymmetric quantum mechanics is used to evaluate new excited states of a non-polynomial potential. This illustrates a method of evaluating higher excited states of quantum mechanical potentials. (A.C.A.S.) [pt

A microscopic model of rate and state friction evolution

Science.gov (United States)

Li, Tianyi; Rubin, Allan M.

2017-08-01

Whether rate- and state-dependent friction evolution is primarily slip dependent or time dependent is not well resolved. Although slide-hold-slide experiments are traditionally interpreted as supporting the aging law, implying time-dependent evolution, recent studies show that this evidence is equivocal. In contrast, the slip law yields extremely good fits to velocity step experiments, although a clear physical picture for slip-dependent friction evolution is lacking. We propose a new microscopic model for rate and state friction evolution in which each asperity has a heterogeneous strength, with individual portions recording the velocity at which they became part of the contact. Assuming an exponential distribution of asperity sizes on the surface, the model produces results essentially similar to the slip law, yielding very good fits to velocity step experiments but not improving much the fits to slide-hold-slide experiments. A numerical kernel for the model is developed, and an analytical expression is obtained for perfect velocity steps, which differs from the slip law expression by a slow-decaying factor. By changing the quantity that determines the intrinsic strength, we use the same model structure to investigate aging-law-like time-dependent evolution. Assuming strength to increase logarithmically with contact age, for two different definitions of age we obtain results for velocity step increases significantly different from the aging law. Interestingly, a solution very close to the aging law is obtained if we apply a third definition of age that we consider to be nonphysical. This suggests that under the current aging law, the state variable is not synonymous with contact age.

Excited-state intramolecular hydrogen transfer (ESIHT) of 1,8-Dihydroxy-9,10-anthraquinone (DHAQ) characterized by ultrafast electronic and vibrational spectroscopy and computational modeling

KAUST Repository

Mohammed, Omar F.

2014-05-01

We combine ultrafast electronic and vibrational spectroscopy and computational modeling to investigate the photoinduced excited-state intramolecular hydrogen-transfer dynamics in 1,8-dihydroxy-9,10-anthraquinone (DHAQ) in tetrachloroethene, acetonitrile, dimethyl sulfoxide, and methanol. We analyze the electronic excited states of DHAQ with various possible hydrogen-bonding schemes and provide a general description of the electronic excited-state dynamics based on a systematic analysis of femtosecond UV/vis and UV/IR pump-probe spectroscopic data. Upon photoabsorption at 400 nm, the S 2 electronic excited state is initially populated, followed by a rapid equilibration within 150 fs through population transfer to the S 1 state where DHAQ exhibits ESIHT dynamics. In this equilibration process, the excited-state population is distributed between the 9,10-quinone (S2) and 1,10-quinone (S1) states while undergoing vibrational energy redistribution, vibrational cooling, and solvation dynamics on the 0.1-50 ps time scale. Transient UV/vis pump-probe data in methanol also suggest additional relaxation dynamics on the subnanosecond time scale, which we tentatively ascribe to hydrogen bond dynamics of DHAQ with the protic solvent, affecting the equilibrium population dynamics within the S2 and S1 electronic excited states. Ultimately, the two excited singlet states decay with a solvent-dependent time constant ranging from 139 to 210 ps. The concomitant electronic ground-state recovery is, however, only partial because a large fraction of the population relaxes to the first triplet state. From the similarity of the time scales involved, we conjecture that the solvent plays a crucial role in breaking the intramolecular hydrogen bond of DHAQ during the S2/S1 relaxation to either the ground or triplet state. © 2014 American Chemical Society.

Luminescence and excited state dynamics in Bi3+-doped LiLaP4O12 phosphates

International Nuclear Information System (INIS)

Babin, V.; Chernenko, K.; Demchenko, P.; Mihokova, E.; Nikl, M.; Pashuk, I.; Shalapska, T.; Voloshinovskii, A.; Zazubovich, S.

2016-01-01

Photo- and X-ray-excited luminescence characteristics of Bi-doped LiLaP 4 O 12 phosphates with different bismuth contents (from 1 to 25 at% in the melt) are investigated in the 4.2–300 K temperature range and compared with the characteristics of the undoped LiLaP 4 O 12 phosphate. The broad 2.95 eV emission band of LiLaP 4 O 12 :Bi excited around 5.4 eV is found to arise from the bismuth dopant. Relatively large FWHM and Stokes shift of the emission band and especially the data on the low-temperature decay kinetics of the 2.95 eV emission and its temperature dependence, indicating a very small spin-orbit splitting energy of the corresponding excited state, allow the conclusion that this emission arises from the radiative decay of the triplet state of an exciton localized around a Bi 3+ ion. No spectral bands are observed, arising from the electron transitions between the energy levels of Bi 3+ ions. Phenomenological model is proposed for the description of the excited state dynamics of the Bi 3+ -related localized exciton in LiLaP 4 O 12 :Bi and the parameters of the triplet localized exciton state are determined. Keywords: Photoluminescence; Time-resolved spectroscopy; Excited states; Bi 3+ centers; LiLaP 4 O 12 :Bi powders

North American NGL exciting times are just ahead

International Nuclear Information System (INIS)

Gist, R.L.; Otto, K.W.

1998-01-01

Although it is a fairly conservative consulting company, Purvin and Gertz believes that exciting times are just ahead for the North American NGL industry. In the United States, NGL production will be rising rapidly, particularly in the Gulf of Mexico offshore from Louisiana. Demand will also be increasing in many sectors, with the largest increases as petrochemical feedstocks. Similarly, in Canada natural gas export pipelines will result in higher gas and NGL production. Petrochemicals will also play a large role in rapidly rising demand for NGL. Lastly, in Mexico quickly growing demand for natural gas to produce electrical power will push up NGL production

Optimal control of peridinin excited-state dynamics

Czech Academy of Sciences Publication Activity Database

Dietzek, B.; Chábera, P.; Hanf, R.; Tschierlei, S.; Popp, J.; Pascher, T.; Yartsev, A.; Polívka, Tomáš

2010-01-01

Roč. 373, 1-2 (2010), s. 129-136 ISSN 0301-0104 Institutional research plan: CEZ:AV0Z50510513 Keywords : peridin * excited-state dynamics * coherent control Subject RIV: BO - Biophysics Impact factor: 2.017, year: 2010

Elucidation of the relationships between H-bonding patterns and excited state dynamics in cyclovalone.

Science.gov (United States)

Lamperti, Marco; Maspero, Angelo; Tønnesen, Hanne H; Bondani, Maria; Nardo, Luca

2014-08-28

Cyclovalone is a synthetic curcumin derivative in which the keto-enolic system is replaced by a cyclohexanone ring. This modification of the chemical structure might in principle result in an excited state that is more stable than that of curcumin, which in turn should produce an enhanced phototoxicity. Indeed, although curcumin exhibits photosensitized antibacterial activity, this compound is characterized by very fast excited-state dynamics which limit its efficacy as a photosensitizer. In previous works we showed that the main non-radiative decay pathway of keto-enolic curcuminoids is through excited-state transfer of the enolic proton to the keto-oxygen. Another effective deactivation pathway involves an intermolecular charge transfer mechanism occurring at the phenyl rings, made possible by intramolecular H-bonding between the methoxy and the hydroxyl substituent. In this paper we present UV-Vis and IR absorption spectra data with the aim of elucidating the intramolecular charge distribution of this compound and its solvation patterns in different environments, with particular focus on solute-solvent H-bonding features. Moreover, we discuss steady state and time-resolved fluorescence data that aim at characterizing the excited-state dynamics of cyclovalone, and we compare its decay photophysics to that of curcumin. Finally, because during the characterization procedures we found evidence of very fast photodegradation of cyclovalone, its photostability in four organic solvents was studied by HPLC and the corresponding relative degradation rates were calculated.

Elucidation of the Relationships between H-Bonding Patterns and Excited State Dynamics in Cyclovalone

Directory of Open Access Journals (Sweden)

Marco Lamperti

2014-08-01

Full Text Available Cyclovalone is a synthetic curcumin derivative in which the keto-enolic system is replaced by a cyclohexanone ring. This modification of the chemical structure might in principle result in an excited state that is more stable than that of curcumin, which in turn should produce an enhanced phototoxicity. Indeed, although curcumin exhibits photosensitized antibacterial activity, this compound is characterized by very fast excited-state dynamics which limit its efficacy as a photosensitizer. In previous works we showed that the main non-radiative decay pathway of keto-enolic curcuminoids is through excited-state transfer of the enolic proton to the keto-oxygen. Another effective deactivation pathway involves an intermolecular charge transfer mechanism occurring at the phenyl rings, made possible by intramolecular H-bonding between the methoxy and the hydroxyl substituent. In this paper we present UV-Vis and IR absorption spectra data with the aim of elucidating the intramolecular charge distribution of this compound and its solvation patterns in different environments, with particular focus on solute-solvent H-bonding features. Moreover, we discuss steady state and time-resolved fluorescence data that aim at characterizing the excited-state dynamics of cyclovalone, and we compare its decay photophysics to that of curcumin. Finally, because during the characterization procedures we found evidence of very fast photodegradation of cyclovalone, its photostability in four organic solvents was studied by HPLC and the corresponding relative degradation rates were calculated.

Anisotropy of electronic states excited in ion-atom collisions

International Nuclear Information System (INIS)

Boskamp, E.B.

1983-01-01

The author reports coincidence measurements made on the He + + Ne and He + + He systems. The complex population amplitudes for the magnetic sublevels of the investigated excited states, Ne(2p 4 3s 2 ) 1 D and He(2p 2 ) 1 D, were completely determined and possible excitation mechanisms are described. (Auth.)

Excited-state quantum phase transitions in systems with two degrees of freedom: Level density, level dynamics, thermal properties

International Nuclear Information System (INIS)

Stránský, Pavel; Macek, Michal; Cejnar, Pavel

2014-01-01

Quantum systems with a finite number of freedom degrees f develop robust singularities in the energy spectrum of excited states as the system’s size increases to infinity. We analyze the general form of these singularities for low f, particularly f=2, clarifying the relation to classical stationary points of the corresponding potential. Signatures in the smoothed energy dependence of the quantum state density and in the flow of energy levels with an arbitrary control parameter are described along with the relevant thermodynamical consequences. The general analysis is illustrated with specific examples of excited-state singularities accompanying the first-order quantum phase transition. -- Highlights: •ESQPTs found in infinite-size limit of systems with low numbers of freedom degrees f. •ESQPTs related to non-analytical evolutions of classical phase–space properties. •ESQPT signatures analyzed for general f, particularly f=2, extending known case f=1. •ESQPT signatures identified in smoothened density and flow of energy spectrum. •ESQPTs shown to induce a new type of thermodynamic anomalies

Can $\\beta$-decay probe excited state halos?

CERN Multimedia

2002-01-01

In the first experiment at the newly constructed ISOLDE Facility the first-forbidden $\\beta$-decay of $^{17}$Ne into the first excited state of $^{17}$F has been measured. It is a factor two faster than the corresponding mirror decay and thus gives one of the largest recorded asymmetries for $\\beta$-decays feeding bound final states. Shell-model calculations can only reproduce the asymmetry if the halo structure of the $^{17}$F state is taken into account.

Ultrafast dynamics of electronically excited molecules and clusters

International Nuclear Information System (INIS)

Lietard, Aude

2014-01-01

This PhD thesis investigated the ultrafast dynamics of photo-chromic molecules and argon clusters in the gas phase at the femtosecond timescale. Pump-probe experiments are performed in a set-up which associates a versatile pulsed molecular beam coupled to a photoelectron/photoion velocity map imager (VMI) and a time-of-flight mass spectrometer (TOF-MS). Theses pump-probe experiments provides the temporal evolution of the electronic distribution for each system of interest. Besides, a modelization has been performed in order to characterize the density and the velocity distribution in the pulsed beam. Regarding the photo-chromic di-thienyl-ethene molecules, parallel electronic relaxation pathways were observed. This contrasts with the observation of sequential relaxation processes in most molecules studied so far. In the present case, the initial wave packet splits in two parts. One part is driven to the ground state at the femtosecond time scale through a conical intersection, and the second part remains for ps in the excited state and experiences oscillations in a suspended well. This study has shed light into the intrinsic dynamics of the molecules under study and a general relaxation mechanism has been proposed, which applies to the whole family of di-thienyl-ethene molecules whatever the state of matter (gas phase or solution) in which they have been investigated. Concerning argon clusters excited at about 14 eV, two behaviors of different time scale have been observed at different time scales. The first one occurs in the first picoseconds of the dynamics. It corresponds to the electronic relaxation of an excitonic state at a rate of 1 eV.ps -1 . The second phenomenon corresponds to the localization of the exciton on the excimer Ar 2 *. This phenomenon is observed 4-5 ps after the excitation. In this study, we also observed the ejection of excited argon atoms, addressing the lifetime of the delocalized excitonic state. This work provide additional informations

Production of autoionizing di-excited states of barium with high angular momentum

International Nuclear Information System (INIS)

Roussel, F.; Breger, P.; Gounand, F.; Spiess, G.

1988-01-01

Autoionizing di-excited states Ba(6p 1/2 27l) with 7 ≤l≤26, have been experimentally detected. They have been produced by a method combining excitation by two lasers and l-mixing collisions between barium and xenon. Results show that a long delay between the two laser excitation steps is favourable to the production of these states. The method has proved to be very efficient (measured cross-section: σ = 3.1 . 10 -13 cm 2 ) for populating high-angular-momentum autoionizing states of barium

Qualitative assessment of ultra-fast non-Grotthuss proton dynamics in S1 excited state of liquid H2O from ab initio time-dependent density functional theory★

Science.gov (United States)

Ziaei, Vafa; Bredow, Thomas

2017-11-01

We study qualitatively ultra-fast proton transfer (PT) in the first singlet (S1) state of liquid water (absorption onset) through excited-state dynamics by means of time-dependent density functional theory and ab initio Born-Oppenheimer molecular dynamics. We find that after the initial excitation, a PT occurs in S1 in form of a rapid jump to a neighboring water molecule, on which the proton either may rest for a relatively long period of time (as a consequence of possible defect in the hydrogen bond network) followed by back and forth hops to its neighboring water molecule or from which it further moves to the next water molecule accompanied by back and forth movements. In this way, the proton may become delocalized over a long water wire branch, followed again by back and forth jumps or short localization on a water molecule for some femtoseconds. As a result, the mechanism of PT in S1 is in most cases highly non-Grotthuss-like, delayed and discrete. Furthermore, upon PT an excess charge is ejected to the solvent trap, the so-called solvated electron. The spatial extent of the ejected solvated electron is mainly localized within one solvent shell with overlappings on the nearest neighbor water molecules and delocalizing (diffuse) tails extending beyond the first solvent sphere. During the entire ultra-short excited-state dynamics the remaining OH radical from the initially excited water molecule exhibits an extremely low mobility and is non-reactive. Supplementary material in the form of one pdf file available from the Journal web page at http://https://doi.org/10.1140/epjb/e2017-80329-7.

Excited-State N2 Dissociation Pathway on Fe-Functionalized Au.

Science.gov (United States)

Martirez, John Mark P; Carter, Emily A

2017-03-29

Localized surface plasmon resonances (LSPRs) offer the possibility of light-activated chemical catalysis on surfaces of strongly plasmonic metal nanoparticles. This technology relies on lower-barrier bond formation and/or dissociation routes made available through energy transfer following the eventual decay of LSPRs. The coupling between these decay processes and a chemical trajectory (nuclear motion, charge-transfer, intersystem crossing, etc.) dictates the availability of these alternative (possibly lower barrier) excited-state channels. The Haber-Bosch method of NH 3 synthesis from N 2 and H 2 is notoriously energy intensive. This is due to the difficulty of N 2 dissociation despite the overall reaction being thermodynamically favorable at ambient temperatures and pressures. LSPRs may provide means to improve the kinetics of N 2 dissociation via induced resonance electronic excitation. In this work, we calculate, via embedded n-electron valence second-order perturbation theory within the density functional embedding theory, the excited-state potential energy surfaces for dissociation of N 2 on an Fe-doped Au(111) surface. This metal alloy may take advantage simultaneously of the strong LSPR of Au and the catalytic activity of Fe toward N 2 dissociation. We find the ground-state dissociation activation energy to be 4.74 eV/N 2 , with Fe as the active site on the surface. Consecutive resonance energy transfers (RETs) may be accessed due to the availability of many electronically excited states with intermediate energies arising from the metal surface that may couple to states induced by the Fe-dopant and the adsorbate molecule, and crossing between excited states may effectively lower the dissociation barrier to 1.33 eV. Our work illustrates that large energetic barriers, prohibitive toward chemical reaction, may be overcome through multiple RETs facilitating an otherwise difficult chemical process.

Electron energy distribution functions and thermalization times in methane and in argon--methane mixtures: An effect of vibrational excitation processes

International Nuclear Information System (INIS)

Krajcar-Bronic, I.; Kimura, M.

1995-01-01

Electron thermalization in methane and argon--methane mixtures is studied by using the Boltzmann equation. The presence of low-lying vibrational excited states in methane significantly changes electron energy distribution functions and relaxation times. We found that (i) the mean electron energy just below the first vibrational excited state is reached faster by 1000 times when the vibrational states are taken into account, and (ii) electron energy distribution functions have distinct peaks at energy intervals equal to the vibrational threshold energies. Both these effects are due to large vibrational stopping cross section. The thermalization time in mixtures of argon--methane (without vibrational states) smoothly changes as the mixture composition varies, and no significant difference in the electron energy distribution function is observed. When the vibrational excited states are taken into account, thermalization is almost completely defined by CH 4 , even at very low fractional concentrations of CH 4 . The sensitivity of the electron energy distribution functions on the momentum transfer cross sections used in calculation on the thermalization is discussed. copyright 1995 American Institute of Physics

Excited State Structural Dynamics of Carotenoids and Charge Transfer Systems

International Nuclear Information System (INIS)

Van Tassle, Aaron Justin

2006-01-01

This dissertation describes the development and implementation of a visible/near infrared pump/mid-infrared probe apparatus. Chapter 1 describes the background and motivation of investigating optically induced structural dynamics, paying specific attention to solvation and the excitation selection rules of highly symmetric molecules such as carotenoids. Chapter 2 describes the development and construction of the experimental apparatus used throughout the remainder of this dissertation. Chapter 3 will discuss the investigation of DCM, a laser dye with a fluorescence signal resulting from a charge transfer state. By studying the dynamics of DCM and of its methyl deuterated isotopomer (an otherwise identical molecule), we are able to investigate the origins of the charge transfer state and provide evidence that it is of the controversial twisted intramolecular (TICT) type. Chapter 4 introduces the use of two-photon excitation to the S1 state, combined with one-photon excitation to the S2 state of the carotenoid beta-apo-8'-carotenal. These 2 investigations show evidence for the formation of solitons, previously unobserved in molecular systems and found only in conducting polymers Chapter 5 presents an investigation of the excited state dynamics of peridinin, the carotenoid responsible for the light harvesting of dinoflagellates. This investigation allows for a more detailed understanding of the importance of structural dynamics of carotenoids in light harvesting

Giant dipole resonances built on excited states

International Nuclear Information System (INIS)

Snover, K.A.

1983-01-01

The properties of giant dipole resonances built on excited nuclear states are reviewed, with emphasis on recent results. Nonstatistical (p,γ) reactions in light nuclei, and statistical complex-particle reactions in light and heavy nuclei are discussed. 27 references

Coherence, energy and charge transfers in de-excitation pathways of electronic excited state of biomolecules in photosynthesis

DEFF Research Database (Denmark)

Bohr, Henrik; Malik, F. Bary

2013-01-01

The observed multiple de-excitation pathways of photo-absorbed electronic excited state in the peridinin–chlorophyll complex, involving both energy and charge transfers among its constituents, are analyzed using the bio-Auger (B-A) theory. It is also shown that the usually used F¨orster–Dexter...

Energy-Looping Nanoparticles: Harnessing Excited-State Absorption for Deep-Tissue Imaging.

Science.gov (United States)

Levy, Elizabeth S; Tajon, Cheryl A; Bischof, Thomas S; Iafrati, Jillian; Fernandez-Bravo, Angel; Garfield, David J; Chamanzar, Maysamreza; Maharbiz, Michel M; Sohal, Vikaas S; Schuck, P James; Cohen, Bruce E; Chan, Emory M

2016-09-27

Near infrared (NIR) microscopy enables noninvasive imaging in tissue, particularly in the NIR-II spectral range (1000-1400 nm) where attenuation due to tissue scattering and absorption is minimized. Lanthanide-doped upconverting nanocrystals are promising deep-tissue imaging probes due to their photostable emission in the visible and NIR, but these materials are not efficiently excited at NIR-II wavelengths due to the dearth of lanthanide ground-state absorption transitions in this window. Here, we develop a class of lanthanide-doped imaging probes that harness an energy-looping mechanism that facilitates excitation at NIR-II wavelengths, such as 1064 nm, that are resonant with excited-state absorption transitions but not ground-state absorption. Using computational methods and combinatorial screening, we have identified Tm(3+)-doped NaYF4 nanoparticles as efficient looping systems that emit at 800 nm under continuous-wave excitation at 1064 nm. Using this benign excitation with standard confocal microscopy, energy-looping nanoparticles (ELNPs) are imaged in cultured mammalian cells and through brain tissue without autofluorescence. The 1 mm imaging depths and 2 μm feature sizes are comparable to those demonstrated by state-of-the-art multiphoton techniques, illustrating that ELNPs are a promising class of NIR probes for high-fidelity visualization in cells and tissue.

Statistical density of nuclear excited states

Directory of Open Access Journals (Sweden)

V. M. Kolomietz

2015-10-01

Full Text Available A semi-classical approximation is applied to the calculations of single-particle and statistical level densities in excited nuclei. Landau's conception of quasi-particles with the nucleon effective mass m* < m is used. The approach provides the correct description of the continuum contribution to the level density for realistic finite-depth potentials. It is shown that the continuum states does not affect significantly the thermodynamic calculations for sufficiently small temperatures T ≤ 1 MeV but reduce strongly the results for the excitation energy at high temperatures. By use of standard Woods - Saxon potential and nucleon effective mass m* = 0.7m the A-dependency of the statistical level density parameter K was evaluated in a good qualitative agreement with experimental data.

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)

Lifetimes of low-lying excited states in 50 36 86Kr

Science.gov (United States)

Henderson, J.; Chester, A.; Ball, G. C.; Caballero-Folch, R.; Domingo, T.; Drake, T. E.; Evitts, L. J.; Garnsworthy, A. B.; Hackman, G.; Hallam, S.; Moukaddam, M.; Ruotsalainen, P.; Smallcombe, J.; Smith, J. K.; Starosta, K.; Svensson, C. E.; Williams, J.

2018-04-01

Background: The evolution of nuclear magic numbers at extremes of isospin is a topic at the forefront of contemporary nuclear physics. N =50 is a prime example, with increasing experimental data coming to light on potentially doubly magic 100Sn and 78Ni at the proton-rich and proton-deficient extremes, respectively; however, experimental discrepancies exist in the data for less exotic systems. Purpose: In 86Kr the B (E 2 ;21+→01+) value—a key indicator of shell evolution—has been experimentally determined by two different methodologies, with the results deviating by 3 σ . Here, we report on a new high-precision measurement of this value, as well as the first measured lifetimes and hence transition strengths for the 22+ and 3(2) - states in the nucleus. Methods: The Doppler-shift attenuation method was implemented using the TRIUMF-ISAC γ -ray escape-suppressed spectrometer (TIGRESS) γ -ray spectrometer and the TIGRESS integrated plunger device. High-statistics Monte Carlo simulations were utilized to extract lifetimes in accordance with state-of-the-art methodologies. Results: Lifetimes of τ (21+)=336 ±4 (stat.)±20 (sys.) fs, τ (22+)=263 ±9 (stat.)±19 (sys.) fs, and τ (3(2) -)=73 ±6 (stat.)±32 (sys.) fs were extracted. This yields a transition strength for the first-excited state of B (E 2 ;21+→01+)=259 ±3 (stat.)±16 (sys.) e2 fm4. Conclusions: The measured lifetime disagrees with the previous Doppler-shift attenuation method measurement by more than 3 σ , while agreeing well with a previous value extracted from Coulomb excitation. The newly extracted B (E 2 ;21+→01+) value indicates a more significant reduction in the N =50 isotones approaching Z =40 .

Excited States and Photodebromination of Selected Polybrominated Diphenyl Ethers: Computational and Quantitative Structure—Property Relationship Studies

Directory of Open Access Journals (Sweden)

Jin Luo

2015-01-01

Full Text Available This paper presents a density functional theory (DFT/time-dependent DFT (TD-DFT study on the lowest lying singlet and triplet excited states of 20 selected polybrominateddiphenyl ether (PBDE congeners, with the solvation effect included in the calculations using the polarized continuum model (PCM. The results obtained showed that for most of the brominated diphenyl ether (BDE congeners, the lowest singlet excited state was initiated by the electron transfer from HOMO to LUMO, involving a π–σ* excitation. In triplet excited states, structure of the BDE congeners differed notably from that of the BDE ground states with one of the specific C–Br bonds bending off the aromatic plane. In addition, the partial least squares regression (PLSR, principal component analysis-multiple linear regression analysis (PCA-MLR, and back propagation artificial neural network (BP-ANN approaches were employed for a quantitative structure-property relationship (QSPR study. Based on the previously reported kinetic data for the debromination by ultraviolet (UV and sunlight, obtained QSPR models exhibited a reasonable evaluation of the photodebromination reactivity even when the BDE congeners had same degree of bromination, albeit different patterns of bromination.

Effects of ligand substitution on the excited state dynamics of the Ru(dcbpy)(CO) 2I 2 complex

Science.gov (United States)

Lehtovuori, Viivi; Kallioinen, Jani; Myllyperkiö, Pasi; Haukka, Matti; Korppi-Tommola, Jouko

2003-11-01

Spectroscopic evidence suggest [PCCP 3 (2001) 1992] that illumination with visible light of the [ trans-I-Ru(dcbpy)(CO) 2I 2] (dcbpy= 4,4 '-dicarboxy-2,2 '-bipyridine) complex in solution induces dissociation of a CO group followed by reorganization of the ligands and attachment of a solvent molecule. In the present study, we report results on excited state dynamics of this ruthenium complex and its photoproduct. Femtosecond transient absorption measurements reveal dominance of excited state absorption of the reactant and the photoproduct [ cis-I-Ru(dcbpy)(CO)(Sol)I 2] (Sol=ethanol or acetonitrile) in the visible spectral region. The time-resolved measurements for the reactant at 77 K indicate interligand charge transfer from mixed Ru-I states to empty dcbpy orbitals. For the photoproduct, no such transfer was observed. In both complexes recovery from the lowest energy excited triplet state to the ground state occurs via two channels: radiative relaxation and a parallel barrier controlled non-radiative relaxation. The barrier is much higher in the reactant (about 850 cm -1) than in the product. A combination of DFT and ZINDO/CI calculations was used to estimate excited singlet and triplet spectra of the reactant and the product molecules. Calculated singlet-triplet difference spectra qualitatively match the observed transient spectra 500 fs after excitation supporting the idea that observed excited state relaxation occurs from the triplet states in both complexes.

Effects of ligand substitution on the excited state dynamics of the Ru(dcbpy)(CO)2I2 complex

International Nuclear Information System (INIS)

Lehtovuori, Viivi; Kallioinen, Jani; Myllyperkioe, Pasi; Haukka, Matti; Korppi-Tommola, Jouko

2003-01-01

Spectroscopic evidence suggest [PCCP 3 (2001) 1992] that illumination with visible light of the [trans-I-Ru(dcbpy)(CO) 2 I 2 ] (dcbpy4,4 ' -dicarboxy-2,2 ' -bipyridine) complex in solution induces dissociation of a CO group followed by reorganization of the ligands and attachment of a solvent molecule. In the present study, we report results on excited state dynamics of this ruthenium complex and its photoproduct. Femtosecond transient absorption measurements reveal dominance of excited state absorption of the reactant and the photoproduct [cis-I-Ru(dcbpy)(CO)(Sol)I 2 ] (Sol=ethanol or acetonitrile) in the visible spectral region. The time-resolved measurements for the reactant at 77 K indicate interligand charge transfer from mixed Ru-I states to empty dcbpy orbitals. For the photoproduct, no such transfer was observed. In both complexes recovery from the lowest energy excited triplet state to the ground state occurs via two channels: radiative relaxation and a parallel barrier controlled non-radiative relaxation. The barrier is much higher in the reactant (about 850 cm -1 ) than in the product. A combination of DFT and ZINDO/CI calculations was used to estimate excited singlet and triplet spectra of the reactant and the product molecules. Calculated singlet-triplet difference spectra qualitatively match the observed transient spectra 500 fs after excitation supporting the idea that observed excited state relaxation occurs from the triplet states in both complexes

One-dimensional multiple-well oscillators: A time-dependent

Indian Academy of Sciences (India)

... quantum mechanical multiple-well oscillators. An imaginary-time evolution technique, coupled with the minimization of energy expectation value to reach a global minimum, subject to orthogonality constraint (for excited states) has been employed. Pseudodegeneracy in symmetric, deep multiple-well potentials, probability ...

Excited-state formation as H+ and He+ ions scatter from metal surfaces

International Nuclear Information System (INIS)

Baird, W.E.; Zivitz, M.; Thomas, E.W.

1975-01-01

Impact of 10-to30KeV H + or He + ions on polycrystalline metal surfaces causes some projectiles to be backscattered in a neutral excited state. These projectiles subsequently radiatively decay, emitting Doppler-broadened spectral lines. By analysis of the spectral shape of these lines, we are able to determine the probability of radiationless deexcitation of the excited backscattered atoms. Quantitative measurements of spectral intensity indicate that less than 1% of all projectiles are backscattered in an excited state. The relative variation of total spectral line intensity with angle of projectile incidence and with projectile primary energy has been successfully predicted using a model which assumes that the probability for excited-state formation is independent of the scattered projectile's energy and direction. The variation in total spectral line intensity with target atomic number is predicted, and the sputtering and excitation of Al under He + impact is briefly examined

Di-lepton yield from the decay of excited 28Si states

International Nuclear Information System (INIS)

Bacelar, J.C.; Buda, A.; Balanda, A.; Krasznahorkay, A.; Ploeg, H. van der; Sujkowski, Z.; Woude, A. van der

1994-01-01

The first dilepton yield measurements from excited nuclear states obtained with a new Positron-Electron Pair Spectroscopic Instrument (PEPSI) are reported. Nuclear states in 28 Si, with an initial excitation energy E * =50 MeV, were populated via the isospin T=0 reaction 4 He+ 24 Mg and the mixed-isospin 3 He+ 25 Mg reaction. In both reactions the dilepton (e + e - ) and photon decay yields were measured concurrently. An excess of counts in the e + e - spectrum, over the converted photon yield, is observed in the energy region above 15 MeV. An analyses is discussed whereby the observed excess counts are assumed to represent the isoscalar E0 strength in excited nuclear states. (orig.)

Fast-timing lifetime measurements of excited states in Cu67

Science.gov (United States)

NiÅ£ǎ, C. R.; Bucurescu, D.; Mǎrginean, N.; Avrigeanu, M.; Bocchi, G.; Bottoni, S.; Bracco, A.; Bruce, A. M.; Cǎta-Danil, G.; Coló, G.; Deleanu, D.; Filipescu, D.; GhiÅ£ǎ, D. G.; Glodariu, T.; Leoni, S.; Mihai, C.; Mason, P. J. R.; Mǎrginean, R.; Negret, A.; Pantelicǎ, D.; Podolyak, Z.; Regan, P. H.; Sava, T.; Stroe, L.; Toma, S.; Ur, C. A.; Wilson, E.

2014-06-01

The half-lives of the 9/2+, 13/2+, and 15/2+ yrast states in the neutron-rich Cu67 nucleus were determined by using the in-beam fast-timing technique. The experimentally deduced E3 transition strength for the decay of the 9/2+ level to the 3/2- ground state indicates that the wave function of this level might contain a collective component arising from the coupling of the odd proton p3/2 with the 3- state in Ni66. Theoretical interpretations of the 9/2+ state are presented within the particle-vibration weak-coupling scheme involving the unpaired proton and the 3- state from Ni66 and within shell-model calculations with a Ni56 core using the jj44b residual interaction. The shell model also accounts reasonably well for the other measured electromagnetic transition probabilities.

Fluorescence detection of single molecules using pulsed near-field optical excitation and time correlated photon counting

International Nuclear Information System (INIS)

Ambrose, W.P.; Goodwin, P.M.; Martin, J.C.; Keller, R.A.

1994-01-01

Pulsed excitation, time correlated single photon counting and time gated detection are used in near-field optical microscopy to enhance fluorescence images and measure the fluorescence lifetimes of single molecules of Rhodamine 6G on silica surfaces. Time gated detection is used to reject prompt scattered background and to improve the image signal to noise ratio. The excited state lifetime of a single Rhodamine 6G molecule is found to depend on the position of the near-field probe. We attribute the lifetime variations to spontaneous emission rate alterations by the fluorescence reflected from and quenching by the aluminum coated probe

Excited-state Raman spectroscopy with and without actinic excitation: S{sub 1} Raman spectra of trans-azobenzene

Energy Technology Data Exchange (ETDEWEB)

Dobryakov, A. L.; Quick, M.; Ioffe, I. N.; Granovsky, A. A.; Ernsting, N. P.; Kovalenko, S. A. [Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, D-12489 Berlin (Germany)

2014-05-14

We show that femtosecond stimulated Raman spectroscopy can record excited-state spectra in the absence of actinic excitation, if the Raman pump is in resonance with an electronic transition. The approach is illustrated by recording S{sub 1} and S{sub 0} spectra of trans-azobenzene in n-hexane. The S{sub 1} spectra were also measured conventionally, upon nπ* (S{sub 0} → S{sub 1}) actinic excitation. The results are discussed and compared to earlier reports.

Excitation dependence of photoluminescence in silicon quantum dots

International Nuclear Information System (INIS)

Wen Xiaoming; Lap Van Dao; Hannaford, Peter; Cho, E-C; Cho, Young H; Green, Martin A

2007-01-01

We have studied the optical properties of silicon quantum dots (QDs) embedded in a silicon oxide matrix using photoluminescence (PL) and time-resolved PL. A broad luminescence band is observed in the red region, in which the time evolution exhibits a stretched exponential decay. With increasing excitation intensity a significant saturation effect is observed. Direct electron-hole recombination is the dominant effect in the red band. A relatively narrow peak appears around 1.5 eV, which is attributed to the interface states overlapping with transition from the ground state of the silicon QDs. The saturation factor increases slowly with detection photon energy between 1.5 and 1.8 eV, which is attributed to the emission from zero-phonon electron-hole recombination. At higher photon energies the significantly increased saturation factor suggests a different emission mechanism, most likely the defect states from silicon, silicon oxide or silicon rich oxide

Sensitivity of (α,α') cross sections to excited-state quadrupole moments

International Nuclear Information System (INIS)

Baker, F.T.; Scott, A.; Ronningen, R.M.; Hamilton, J.H.; Kruse, T.H.; Suchannek, R.; Savin, W.

1977-01-01

Inelastic α particle scattering at 21 and 24 MeV has been used to estimate the electric quadrupole moment of the second 2 + state in 180 Hf. Sensitivity to the assumed quadrupole moment is due almost entirely to reorientation via the nuclear force. Results suggest that the technique may be a useful method of estimating excited state quadrupole moments, particularly for states with high excitation energies or with J greater than 2

Collisional excitation transfer between Rb(5P) states in 50–3000 Torr of 4He

International Nuclear Information System (INIS)

Sell, J F; Gearba, M A; Patterson, B M; Byrne, D; Jemo, G; Meeter, R; Knize, R J; Lilly, T C

2012-01-01

Measurements of the mixing rates and cross sections for collisional excitation transfer between the 5P 1/2 and 5P 3/2 states of rubidium (Rb) in the presence of 4 He buffer gas are presented. Selected pulses from a high repetition rate, mode-locked femtosecond laser are used to excite either Rb state with the fluorescence due to collisional excitation transfer observed by time-correlated single-photon counting. The time dependence of this fluorescence is fitted to the solution of rate equations which include the mixing rate, atomic lifetimes and any quenching processes. The variation in the mixing rate over a large range of buffer gas densities allows the determination of both the binary collisional transfer cross section and a three-body collisional transfer rate. We do not observe any collisional quenching effects at 4 He pressures up to 6 atm and discuss in detail other systematic effects considered in the experiment. (paper)

High-Yield Excited Triplet States in Pentacene Self-Assembled Monolayers on Gold Nanoparticles through Singlet Exciton Fission.

Science.gov (United States)

Kato, Daiki; Sakai, Hayato; Tkachenko, Nikolai V; Hasobe, Taku

2016-04-18

One of the major drawbacks of organic-dye-modified self-assembled monolayers on metal nanoparticles when employed for efficient use of light energy is the fact that singlet excited states on dye molecules can be easily deactivated by means of energy transfer to the metal surface. In this study, a series of 6,13-bis(triisopropylsilylethynyl)pentacene-alkanethiolate monolayer protected gold nanoparticles with different particle sizes and alkane chain lengths were successfully synthesized and were employed for the efficient generation of excited triplet states of the pentacene derivatives by singlet fission. Time-resolved transient absorption measurements revealed the formation of excited triplet states in high yield (172±26 %) by suppressing energy transfer to the gold surface. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Long-Lived Triplet Excited States of Bent-Shaped Pentacene Dimers by Intramolecular Singlet Fission.

Science.gov (United States)

Sakuma, Takao; Sakai, Hayato; Araki, Yasuyuki; Mori, Tadashi; Wada, Takehiko; Tkachenko, Nikolai V; Hasobe, Taku

2016-03-24

Intramolecular singlet fission (ISF) is a promising photophysical process to construct more efficient light energy conversion systems as one excited singlet state converts into two excited triplet states. Herein we synthesized and evaluated bent-shaped pentacene dimers as a prototype of ISF to reveal intrinsic characters of triplet states (e.g., lifetimes of triplet excited states). In this study, meta-phenylene-bridged TIPS-pentacene dimer (PcD-3Ph) and 2,2'-bipheynyl bridged TIPS-pentacene dimer (PcD-Biph) were newly synthesized as bent-shaped dimers. In the steady-state spectroscopy, absorption and emission bands of these dimers were fully characterized, suggesting the appropriate degree of electronic coupling between pentacene moieties in these dimers. In addition, the electrochemical measurements were also performed to check the electronic interaction between two pentacene moieties. Whereas the successive two oxidation peaks owing to the delocalization were observed in a directly linked-pentacene dimer (PcD) by a single bond, the cyclic voltammograms in PcD-Biph and PcD-3Ph implied the weaker interaction compared to that of p-phenylene-bridged TIPS-pentacene dimer (PcD-4Ph) and PcD. The femtosecond and nanosecond transient absorption spectra clearly revealed the slower ISF process in bent-shaped pentacene dimers (PcD-Biph and PcD-3Ph), more notably, the slower relaxation of the excited triplet states in PcD-Biph and PcD-3Ph. Namely, the quantum yields of triplet states (ΦT) by ISF approximately remain constant (ca. 180-200%) in all dimer systems, whereas the lifetimes of the triplet excited states became much longer (up to 360 ns) in PcD-Biph as compared to PcD-4Ph (15 ns). Additionally, the lifetimes of the corresponding triplet states in PcD-Biph and PcD-3Ph were sufficiently affected by solvent viscosity. In particular, the lifetimes of PcD-Biph triplet state in THF/paraffin (1.0 μs) increased up to approximately three times as compared to that in THF

Finite-element time evolution operator for the anharmonic oscillator

Science.gov (United States)

Milton, Kimball A.

1995-01-01

The finite-element approach to lattice field theory is both highly accurate (relative errors approximately 1/N(exp 2), where N is the number of lattice points) and exactly unitary (in the sense that canonical commutation relations are exactly preserved at the lattice sites). In this talk I construct matrix elements for dynamical variables and for the time evolution operator for the anharmonic oscillator, for which the continuum Hamiltonian is H = p(exp 2)/2 + lambda q(exp 4)/4. Construction of such matrix elements does not require solving the implicit equations of motion. Low order approximations turn out to be extremely accurate. For example, the matrix element of the time evolution operator in the harmonic oscillator ground state gives a results for the anharmonic oscillator ground state energy accurate to better than 1 percent, while a two-state approximation reduces the error to less than 0.1 percent.

Energies and lifetimes of excited states in copperlike Kr VIII

International Nuclear Information System (INIS)

Livingston, A.E.; Curtis, L.J.; Schectman, R.M.; Berry, H.G.

1980-01-01

The spectrum of Kr VIII has been observed between 180 and 2000 A by using foil excitation of 2.5--3.5-MeV krypton ions. Twenty new transitions have been classified and eleven new excited-state energies have been determined within the n=4 --7 shells. The ionization potential is derived to be 1 015 800 +- 200 cm -1 . The excited-state energies and fine structures are compared with recent relativistic Hartree-Fock calculations. The 4p-state lifetime has been measured by performing a simultaneous analysis of decay data for the 4p level and for its dominant cascade-repopulating levels. The 4p lifetime is found to be 30% shorter than previously measured values and is in excellent agreement with the result of a recent multiconfiguration Hartree-Fock calculation. The source of the discrepancy between this result and earlier measurements is discussed

Cross sections for the vibrational excitation of the H2 X 1Σ+g(v) levels generated by electron collisional excitation of the higher singlet states

International Nuclear Information System (INIS)

Hiskes, J.R.

1991-01-01

The excitation cross sections, σ(v,v double-prime), for an H 2 molecule initially in any one of the 15 vibrational levels, v belonging to the ground electronic state and excited to a final vibrational level, v double-prime are evaluated for direct excitations via all members of the excited electronic singlet spectrum. Account is taken of predissociation, autoionization, and radiative decay of the excited electronic spectrum that leads to a final population distribution for the ground electronic state, X 1 Σ + g (v double-prime). For v=0, account is taken explicitly of transitions via the B, C, B', and D electronic states in evaluating the cross sections. The additional contribution of excitations via all Rydberg states lying above the D state enhances these cross sections by approximately 10%. For v>0, cross sections are evaluated taking explicit account of transitions through the B and C states; higher singlet excitations enhance these values by 25%. The choice of the reference total cross sections remains a subjective one, causing the values calculated here to have a possible uncertainty of +20% -30% . For excitations occurring within a hydrogen discharge, collisional excitation-ionization events among the intermediate singlet states will effectively quench the v, v double-prime excitation process for discharge densities in excess of the range 10 15 --10 16 electrons/cm -3

Watson-Crick base pairing controls excited-state decay in natural DNA.

Science.gov (United States)

Bucher, Dominik B; Schlueter, Alexander; Carell, Thomas; Zinth, Wolfgang

2014-10-13

Excited-state dynamics are essential to understanding the formation of DNA lesions induced by UV light. By using femtosecond IR spectroscopy, it was possible to determine the lifetimes of the excited states of all four bases in the double-stranded environment of natural DNA. After UV excitation of the DNA duplex, we detected a concerted decay of base pairs connected by Watson-Crick hydrogen bonds. A comparison of single- and double-stranded DNA showed that the reactive charge-transfer states formed in the single strands are suppressed by base pairing in the duplex. The strong influence of the Watson-Crick hydrogen bonds indicates that proton transfer opens an efficient decay path in the duplex that prohibits the formation or reduces the lifetime of reactive charge-transfer states. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electron affinity and excited states of methylglyoxal

Science.gov (United States)

Dauletyarov, Yerbolat; Dixon, Andrew R.; Wallace, Adam A.; Sanov, Andrei

2017-07-01

Using photoelectron imaging spectroscopy, we characterized the anion of methylglyoxal (X2A″ electronic state) and three lowest electronic states of the neutral methylglyoxal molecule: the closed-shell singlet ground state (X1A'), the lowest triplet state (a3A″), and the open-shell singlet state (A1A″). The adiabatic electron affinity (EA) of the ground state, EA(X1A') = 0.87(1) eV, spectroscopically determined for the first time, compares to 1.10(2) eV for unsubstituted glyoxal. The EAs (adiabatic attachment energies) of two excited states of methylglyoxal were also determined: EA(a3A″) = 3.27(2) eV and EA(A1A″) = 3.614(9) eV. The photodetachment of the anion to each of these two states produces the neutral species near the respective structural equilibria; hence, the a3A″ ← X2A″ and A1A″ ← X2A″ photodetachment transitions are dominated by intense peaks at their respective origins. The lowest-energy photodetachment transition, on the other hand, involves significant geometry relaxation in the X1A' state, which corresponds to a 60° internal rotation of the methyl group, compared to the anion structure. Accordingly, the X1A' ← X2A″ transition is characterized as a broad, congested band, whose vertical detachment energy, VDE = 1.20(4) eV, significantly exceeds the adiabatic EA. The experimental results are in excellent agreement with the ab initio predictions using several equation-of-motion methodologies, combined with coupled-cluster theory.

Ioniclike energy structure of neutral core-excited states in free Kr clusters

International Nuclear Information System (INIS)

Peredkov, S.; Sorensen, S.L.; Kivimaeki, A.; Schulz, J.; Maartensson, N.; Oehrwall, G.; Lundwall, M.; Rander, T.; Lindblad, A.; Bergersen, H.; Svensson, S.; Bjoerneholm, O.; Tchaplyguine, M.

2005-01-01

The development of electronic states in krypton clusters is investigated by high-resolution core-level electron spectroscopy. The energy ordering of bulk versus surface 3d -1 np(n>5) core-excited states in neutral clusters is demonstrated to be reversed to the 3d -1 5p level situation. The cluster 3d -1 6p,7p states are proven to be at a lower energy than the corresponding atomic levels. These findings reveal the ioniclike energy structure of the neutral cluster core-excited levels. The phenomenon is explained by a spatial spread of the excited orbitals over the cluster lattice

Clustered chimera states in systems of type-I excitability

International Nuclear Information System (INIS)

Vüllings, Andrea; Omelchenko, Iryna; Hövel, Philipp; Hizanidis, Johanne

2014-01-01

The chimera state is a fascinating phenomenon of coexisting synchronized and desynchronized behaviour that was discovered in networks of nonlocally coupled identical phase oscillators over ten years ago. Since then, chimeras have been found in numerous theoretical and experimental studies and more recently in models of neuronal dynamics as well. In this work, we consider a generic model for a saddle-node bifurcation on a limit cycle representative of neural excitability type I. We obtain chimera states with multiple coherent regions (clustered chimeras/multi-chimeras) depending on the distance from the excitability threshold, the range of nonlocal coupling and the coupling strength. A detailed stability diagram for these chimera states and other interesting coexisting patterns (like traveling waves) is presented. (paper)

Excited state fluorescence quenching of the U O2++ ion by monovalent anions

International Nuclear Information System (INIS)

Santarine, G.A.

1987-01-01

The reactions of the Uranyl ion U O 2 ++ in the excited state with the monovalent inorganic ions N O 3 - and I O 3 - in aqueous solutions at normal temperature were studied, using three techniques: Fluorescence in the steady state - Flash photolysis - Fluorescence decay after excitation. With increasing concentration of these ions it was observed a decrease in the normalized intensity and a decrease in the decay time of the fluorescence of the Uranyl ion in the solution and a corresponding appearance of the radicals N O 3 . or I O 3 . . In each case the radical was identified by its optical absorption spectrum. These results suggest that the quenching of fluorescence of the Uranyl ion in each case is owing to an electron transfer reaction. In the case of the Nitrate ion the transfer may occur after the formation of an ionic par (U O 2 + ...N O 3 ) in the ground state. Evidence for static quenching in the system Uranyl iodate was not forthcoming. A mechanism for the determination of the velocity constant (probability per ion pair per unit time) is proposed for each of the systems. (author)

Trapping Dynamics in Photosystem I-Light Harvesting Complex I of Higher Plants Is Governed by the Competition Between Excited State Diffusion from Low Energy States and Photochemical Charge Separation.

Science.gov (United States)

Molotokaite, Egle; Remelli, William; Casazza, Anna Paola; Zucchelli, Giuseppe; Polli, Dario; Cerullo, Giulio; Santabarbara, Stefano

2017-10-26

The dynamics of excited state equilibration and primary photochemical trapping have been investigated in the photosystem I-light harvesting complex I isolated from spinach, by the complementary time-resolved fluorescence and transient absorption approaches. The combined analysis of the experimental data indicates that the excited state decay is described by lifetimes in the ranges of 12-16 ps, 32-36 ps, and 64-77 ps, for both detection methods, whereas faster components, having lifetimes of 550-780 fs and 4.2-5.2 ps, are resolved only by transient absorption. A unified model capable of describing both the fluorescence and the absorption dynamics has been developed. From this model it appears that the majority of excited state equilibration between the bulk of the antenna pigments and the reaction center occurs in less than 2 ps, that the primary charge separated state is populated in ∼4 ps, and that the charge stabilization by electron transfer is completed in ∼70 ps. Energy equilibration dynamics associated with the long wavelength absorbing/emitting forms harbored by the PSI external antenna are also characterized by a time mean lifetime of ∼75 ps, thus overlapping with radical pair charge stabilization reactions. Even in the presence of a kinetic bottleneck for energy equilibration, the excited state dynamics are shown to be principally trap-limited. However, direct excitation of the low energy chlorophyll forms is predicted to lengthen significantly (∼2-folds) the average trapping time.

The triplet excited state of bilirubin

International Nuclear Information System (INIS)

Land, E.J.

1976-01-01

Pulse radiolysis of benzene solutions of 40 μM bilirubin alone or with 0.1 M biphenyl has yielded evidence for the formation of the triplet excited state of bilirubin. Measurements were made of a number of properties, including the absorption spectrum (lambdasub(max)500nm), lifetime 9μs), extinction coefficient (8800 M -1 cm -1 ), energy level (approximately 150 kJ mol -1 ) and the rate of quenching by oxygen (rate constant, 8.2 x 10 8 M -1 s -1 ). An upper limit of 0.1 has also been obtained for the singlet to triplet crossover efficiency of bilirubin following excitation by 353 nm radiation. Consideration is given to the relevance of these data to the mechanism of bilirubin photo-destruction, both in vivo and in vitro. (U.K.)

Evolution of the Collectivity around 68Ni: role of intruder states

International Nuclear Information System (INIS)

Dijon, A.

2012-01-01

The evolution of magic numbers as a function of the neutron number for a given chain of isotopes is one of the major goals of nuclear physics today. Changing magic numbers may lead to profound modifications in the structure of exotic nuclei and manifest themselves experimentally in rapid changes of collectivity and shapes. In this thesis we have studied nuclei around 68 Ni produced in deep inelastic collisions at GANIL. The nuclei of interest were selected and identified by the large acceptance VAMOS recoil spectrometer. Their structure was studied via the detection of the gamma rays emitted at the target point by the EXOGAM array. In one of the two experiments we also installed a specific setup dedicated to the measurements of the delayed gamma rays emitted by the nuclei after their implantation at the focal plane of VAMOS. In the first experiment we have observed a new isomeric state in 68 Ni with a proton intruder configuration at an excitation energy which sensitively depends on the Z=28 and N=40 shell gaps. New transitions were also identified in odd-mass isotopes of Co, Fe and Mn. In the second experiment we have measured the lifetimes of the first-excited states in 63,65 Co using the recoil distance Doppler shift method. From these lifetimes electromagnetic transition probabilities could be deduced, which in turn shed light on the collectivity of the studied isotopes. Comparisons with the shell model and with mean field calculations were carried and provided additional information on the proton-neutron interaction as well as on the evolution of the collectivity in this mass region. (author) [fr

Technique for description of nonrotational excited states in a semiphenomenological nuclear theory

International Nuclear Information System (INIS)

Krutov, V.A.

1985-01-01

A non-standard technique for microscopic description of excited nonrotational states is considered; it is suitable for inseparable force application. Besides, an additional binding operator, mixing quasi-particle excitations and E1-resonance states, is considered. Instead of the standard technique of state ''collectivization'' of the random phase approximation type it is used the so-called ''method of bound amplitudes''

Non-orthogonal configuration interaction for the calculation of multielectron excited states

Energy Technology Data Exchange (ETDEWEB)

Sundstrom, Eric J., E-mail: eric.jon.sundstrom@berkeley.edu; Head-Gordon, Martin [Department of Chemistry, University of California Berkeley, Berkeley, California 94720, USA and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2014-03-21

We apply Non-orthogonal Configuration Interaction (NOCI) to molecular systems where multielectron excitations, in this case double excitations, play a substantial role: the linear polyenes and β-carotene. We demonstrate that NOCI when applied to systems with extended conjugation, provides a qualitatively correct wavefunction at a fraction of the cost of many other multireference treatments. We also present a new extension to this method allowing for purification of higher-order spin states by utilizing Generalized Hartree-Fock Slater determinants and the details for computing 〈S{sup 2}〉 for the ground and excited states.

Excited State s-cis Rotamers Produced by Extreme Red Edge Excitation of all-trans-1,4-Diphenyl-1,3-butadiene

DEFF Research Database (Denmark)

Wallace-Williams, Stacie E.; Møller, Søren; Goldbeck, Robert A.

1993-01-01

with the wavelength independence observed for the excited singlet-state absorption and fluorescence emission spectra of 1,5-diphenyl-2,3,4,6,7,8- hexahydronaphthalene and for the fluorescence emission spectra of 1,4diphenyl-1,3-cyclopentadiene, s-trans and s-cis structural analogs of DPB, respectively. The spectral...... changes in DPB can be explained in terms of an excitation wavelength-dependent production of s-cis and s-trans rotamer populations in the excited state. The DPB fluorescence emission spectrum was resolved into s-cis and s-trans components. The vibronic structure of the s-cis fluorescence spectrum...... is similar to that of s-trans, but the band origin is red-shifted and there is a slightly larger amplitude on the red edge. The excited-state absorption spectrum of s-cis DPB appears to be red-shifted relative to that of s-trans DPB as well....

On the dynamics of excited atoms in time dependent electromagnetic fields

Energy Technology Data Exchange (ETDEWEB)

Foerre, Morten

2004-06-01

This thesis is composed of seven scientific publications written in the period 2001-2004. The focus has been set on Rydberg atoms of hydrogen and lithium in relatively weak electromagnetic fields. Such atoms have been studied extensively during many years, both experimentally and theoretically, They are relatively easy to handle in the laboratory. Their willingness to react to conventional field sources and their long lifetimes, are two reasons for this. Much new insight into fundamental quantum mechanics has been extracted from such studies. By exciting a non-hydrogenic ground state atom or molecule into a highly excited state, many properties of atomic hydrogen are adopted. In many cases the dynamics of such systems can be accurately described by the hydrogenic theory, or alternatively by some slightly modified version like quantum defect theory. In such theories the Rydberg electron(s) of the non-hydrogenic Rydberg system is treated like it is confined in a modified Coulomb potential, which arises from the non-hydrogenic core. defined by the non-excited electrons and the nucleus. The more heavily bound core electrons are less influenced from external perturbations than the excited electrons, giving rise to the so-called frozen-core approximation. where the total effect of the core electrons is put into a modified Coulomb potential. A major part of this thesis has been allocated to the study of core effects in highly excited states of lithium. In collaboration with time experimental group of Erik Horsdal-Pedersen at Aarhus University, we have considered several hydrogenic and non-hydrogenic aspects of such states, when exposed to weak slowly varying electromagnetic fields. The dynamics was restricted to one principal shell (intrashell). Two general features were observed, either the hydrogenic theory applied or alternatively, in case of massive deviation, the dynamics was accurately described by quantum defect theory, clearly demonstrating the usefulness of such

On the dynamics of excited atoms in time dependent electromagnetic fields

International Nuclear Information System (INIS)

Foerre, Morten

2004-06-01

This thesis is composed of seven scientific publications written in the period 2001-2004. The focus has been set on Rydberg atoms of hydrogen and lithium in relatively weak electromagnetic fields. Such atoms have been studied extensively during many years, both experimentally and theoretically, They are relatively easy to handle in the laboratory. Their willingness to react to conventional field sources and their long lifetimes, are two reasons for this. Much new insight into fundamental quantum mechanics has been extracted from such studies. By exciting a non-hydrogenic ground state atom or molecule into a highly excited state, many properties of atomic hydrogen are adopted. In many cases the dynamics of such systems can be accurately described by the hydrogenic theory, or alternatively by some slightly modified version like quantum defect theory. In such theories the Rydberg electron(s) of the non-hydrogenic Rydberg system is treated like it is confined in a modified Coulomb potential, which arises from the non-hydrogenic core. defined by the non-excited electrons and the nucleus. The more heavily bound core electrons are less influenced from external perturbations than the excited electrons, giving rise to the so-called frozen-core approximation. where the total effect of the core electrons is put into a modified Coulomb potential. A major part of this thesis has been allocated to the study of core effects in highly excited states of lithium. In collaboration with time experimental group of Erik Horsdal-Pedersen at Aarhus University, we have considered several hydrogenic and non-hydrogenic aspects of such states, when exposed to weak slowly varying electromagnetic fields. The dynamics was restricted to one principal shell (intrashell). Two general features were observed, either the hydrogenic theory applied or alternatively, in case of massive deviation, the dynamics was accurately described by quantum defect theory, clearly demonstrating the usefulness of such

New results for double-beta decay of 100Mo to excited final states of 100Ru using the TUNL-ITEP apparatus

International Nuclear Information System (INIS)

Kidd, M.F.; Esterline, J.H.; Tornow, W.; Barabash, A.S.; Umatov, V.I.

2009-01-01

The coincidence detection efficiency of the TUNL-ITEP apparatus designed for measuring half-life times of two-neutrino double-beta (2νββ) decay transitions to excited final states in daughter nuclei has been measured with a factor of 2.4 improved accuracy. In addition, the previous measuring time of 455 days for the study of the 100 Mo 2νββ decay to the first excited 0 1 + state in 100 Ru has been increased by 450 days, and a new result (combined with the previous measurement obtained with the same apparatus) for this transition is presented: T 1/2 =[5.5 -0.8 +1.2 (stat)±0.3(syst)]x10 20 yr. Measured 2νββ decay half-life times to excited states can be used to test the reliability of nuclear matrix element calculations needed for determining the effective neutrino mass from zero-neutrino double-beta decay data. We also present new limits for transitions to higher excited states in 100 Ru which, if improved, may be of interest for more exotic conjectures, like a bosonic component to neutrino statistics.

Lifetime measurement of the cesium 6P3/2 state using ultrafast laser-pulse excitation and ionization

International Nuclear Information System (INIS)

Sell, J. F.; Patterson, B. M.; Ehrenreich, T.; Brooke, G.; Scoville, J.; Knize, R. J.

2011-01-01

We report a precision measurement of the cesium 6P 3/2 excited-state lifetime. Two collimated, counterpropagating thermal Cs beams cross perpendicularly to femtosecond pulsed laser beams. High timing accuracy is achieved from having excitation and ionization laser pulses which originate from the same mode-locked laser. Using pulse selection we vary the separation in time between excitation and ionization laser pulses while counting the ions produced. We obtain a Cs 6P 3/2 lifetime of 30.460(38) ns, which is a factor of two improvement from previous measurements and with an uncertainty of 0.12%, is one of the most accurate lifetime measurements on record.

Study of highly excited high spin states via the (HI, α) reaction

International Nuclear Information System (INIS)

Kubono, S.

1982-01-01

Three subjects are discussed in this paper. 1) The mechanism of (HI, α) reactions is briefly studied. 2) Possible excitation of molecular resonance states of 12 C- 12 C in 24 Mg through the 12 C( 16 O, α) 24 Mg reaction were investigated. A precise measurement of the level widths in 24 Mg did not support the previous report that the molecular states seen in 12 C + 12 C scattering had been excited in the transfer reaction 12 C( 16 O, α) 24 Mg. 3) Highly excited states in 28 Si, which have a large parentage of 12 C- 16 O, were also studied via the 12 C( 20 Ne, α) 28 Si reaction. An angular correlation measurement revealed the lowest 8 + and 10 + states at 14.00 and 15.97 MeV, respectively, which were selectively excited in the 12 C( 20 Ne, α) reaction. These results suggest a possible new band in 28 Si. (author)

Unveiling the excited state energy transfer pathways in peridinin-chlorophyll a-protein by ultrafast multi-pulse transient absorption spectroscopy.

Science.gov (United States)

Redeckas, Kipras; Voiciuk, Vladislava; Zigmantas, Donatas; Hiller, Roger G; Vengris, Mikas

2017-04-01

Time-resolved multi-pulse methods were applied to investigate the excited state dynamics, the interstate couplings, and the excited state energy transfer pathways between the light-harvesting pigments in peridinin-chlorophyll a-protein (PCP). The utilized pump-dump-probe techniques are based on perturbation of the regular PCP energy transfer pathway. The PCP complexes were initially excited with an ultrashort pulse, resonant to the S 0 →S 2 transition of the carotenoid peridinin. A portion of the peridinin-based emissive intramolecular charge transfer (ICT) state was then depopulated by applying an ultrashort NIR pulse that perturbed the interaction between S 1 and ICT states and the energy flow from the carotenoids to the chlorophylls. The presented data indicate that the peridinin S 1 and ICT states are spectrally distinct and coexist in an excited state equilibrium in the PCP complex. Moreover, numeric analysis of the experimental data asserts ICT→Chl-a as the main energy transfer pathway in the photoexcited PCP systems. Copyright © 2017 Elsevier B.V. All rights reserved.

Characterising excited states in and around the semi-magic nucleus $^{68}$ Ni using Coulomb excitation and one-neutron transfer

CERN Multimedia

It is proposed to investigate the structure of excited states in $^{68, 70}$Ni(Z =28, N=40, 42) via the measurement of electromagnetic matrix elements in a Coulomb excitation experiment in order to study the N = 40 harmonic-oscillator shell and the Z = 28 proton shell closures. The measured B(E2) values connecting low-lying 0$^{+}$ and 2$^{+}$ can be compared to shell-model predictions. It is also proposed to perform the one-neutron transfer reaction ${d}$($^{68}$Ni,$^{69}$Ni)${p}$, with the aim of populating excited states in $^{69}$Ni. Comparisons with the states populated in the recently performed ${d}$($^{66}$Ni,$^{67}$Ni)${p}$ reaction will be useful in determining the role of the neutron $d_{5/2}$ orbital in the semi-magic properties of $^{68}$Ni.

Coherent excitation of a single atom to a Rydberg state

DEFF Research Database (Denmark)

Miroshnychenko, Yevhen; Gaëtan, Alpha; Evellin, Charles

2010-01-01

We present the coherent excitation of a single Rubidium atom to the Rydberg state 58d3/2 using a two-photon transition. The experimental setup is described in detail, as are experimental techniques and procedures. The coherence of the excitation is revealed by observing Rabi oscillations between...

Some studies on the formation of excited states of aromatic solutes in hydrocarbons and other solvents

Energy Technology Data Exchange (ETDEWEB)

Salmon, G A [Leeds Univ. (UK). Cookridge High Energy Radiation Research Centre

1976-01-01

This paper reviews the work of the author and his co-workers on the radiation-induced formation of excited states of aromatic compounds in solution. The experimental methods used are surveyed and in particular the method of measuring the yields of triplet and singlet excited states of the solute are described. The problems discussed are: (1) the effect of solvent on the yields of excited states, (2) formation of excited states in cyclohexane and other alicyclic hydrocarbons, (3) the formation of excited states in benzene and (4) the identification of T-T absorption spectra.

Excitation of spin-1 states in 166168170Er using bremsstrahlung

International Nuclear Information System (INIS)

Metzger, F.R.

1976-01-01

Some 40 states in 166 , 168 , 170 Er, most of them previously unknown, have been excited using bremsstrahlung with < or =4.2 MeV endpoint energy. For all but three of these levels, the angular distribution of the resonantly scattered radiation favors the assignment of spin 1. For some of the strongly excited levels, linear polarization measurements have been performed. They indicate that these levels have positive parity. The branching ratios further characterize them as K=1 excitations

Rearrangements in ground and excited states

CERN Document Server

de Mayo, Paul

1980-01-01

Rearrangements in Ground and Excited States, Volume 2 covers essays on the theoretical approach of rearrangements; the rearrangements involving boron; and the molecular rearrangements of organosilicon compounds. The book also includes essays on the polytopal rearrangement at phosphorus; the rearrangement in coordination complexes; and the reversible thermal intramolecular rearrangements of metal carbonyls. Chemists and people involved in the study of rearrangements will find the book invaluable.

Tracking excited-state charge and spin dynamics in iron coordination complexes

DEFF Research Database (Denmark)

Zhang, Wenkai; Alonso-Mori, Roberto; Bergmann, Uwe

2014-01-01

to spin state, can elucidate the spin crossover dynamics of [Fe(2,2'-bipyridine)(3)](2+) on photoinduced metal-to-ligand charge transfer excitation. We are able to track the charge and spin dynamics, and establish the critical role of intermediate spin states in the crossover mechanism. We anticipate......Crucial to many light-driven processes in transition metal complexes is the absorption and dissipation of energy by 3d electrons(1-4). But a detailed understanding of such non-equilibrium excited-state dynamics and their interplay with structural changes is challenging: a multitude of excited...... states and possible transitions result in phenomena too complex to unravel when faced with the indirect sensitivity of optical spectroscopy to spin dynamics(5) and the flux limitations of ultrafast X-ray sources(6,7). Such a situation exists for archetypal poly-pyridyl iron complexes, such as [Fe(2...

Coherent photoluminescence excitation spectroscopy of semicrystalline polymeric semiconductors

Science.gov (United States)

Silva, Carlos; Grégoire, Pascal; Thouin, Félix

In polymeric semiconductors, the competition between through-bond (intrachain) and through-space (interchain) electronic coupling determines two-dimensional spatial coherence of excitons. The balance of intra- and interchain excitonic coupling depends very sensitively on solid-state microstructure of the polymer film (polycrystalline, semicrystalline with amorphous domains, etc.). Regioregular poly(3-hexylthiophene) has emerged as a model material because its photoluminescence (PL) spectral lineshape reveals intricate information on the magnitude of excitonic coupling, the extent of energetic disorder, and on the extent to which the disordered energy landscape is correlated. I discuss implementation of coherent two-dimensional electronic spectroscopy. We identify cross peaks between 0-0 and 0-1 excitation peaks, and we measure their time evolution, which we interpret within the context of a hybrid HJ aggregate model. By measurement of the homogeneous linewidth in diverse polymer microstructures, we address the nature of optical transitions within such hynbrid aggregate model. These depend strongly on sample processing, and I discuss the relationship between microstructure, steady-state absorption and PL spectral lineshape, and 2D coherent PL excitation spectral lineshapes.

Two-electron excitation in slow ion-atom collisions: Excitation mechanisms and interferences among autoionizing states

International Nuclear Information System (INIS)

Kimura, M.; Rice Univ., Houston, TX

1990-01-01

The two-electron capture or excitation process resulting from collisions of H + and O 6+ ions with He atoms in the energy range from 0.5 keV/amu to 5 keV/amu is studied within a molecular representation. The collision dynamics for formation of doubly excited O 4+ ions and He** atoms and their (n ell, n'ell ') populations are analyzed in conjunction with electron correlations. Autoionizing states thus formed decay through the Auger process. An experimental study of an ejected electron energy spectrum shows ample structures in addition to two characteristic peaks that are identified by atomic and molecular autoionizations. These structures are attributable to various interferences among electronic states and trajectories. We examine the dominant sources of the interferences. 12 refs., 5 figs

Using narrowband excitation to confirm that the S∗ state in carotenoids is not a vibrationally-excited ground state species

Science.gov (United States)

Jailaubekov, Askat E.; Song, Sang-Hun; Vengris, Mikas; Cogdell, Richard J.; Larsen, Delmar S.

2010-02-01

The hypothesis that S∗ is a vibrationally-excited ground-state population is tested and discarded for two carotenoid samples: β-carotene in solution and rhodopin glucoside embedded in the light harvesting 2 protein from Rhodopseudomonas acidophila. By demonstrating that the transient absorption signals measured in both systems that are induced by broadband (1000 cm -1) and narrowband (50 cm -1) excitation pulses are near identical and hence bandwidth independent, the impulsive stimulated Raman scattering mechanism proposed as the primary source for S∗ generation is discarded. To support this conclusion, previously published multi-pulse pump-dump-probe signals [17] are revisited to discard secondary mechanisms for S∗ formation.

Self-energy correction to the hyperfine splitting for excited states

International Nuclear Information System (INIS)

Wundt, B. J.; Jentschura, U. D.

2011-01-01

The self-energy corrections to the hyperfine splitting is evaluated for higher excited states in hydrogenlike ions using an expansion in the binding parameter Zα, where Z is the nuclear-charge number and α is the fine-structure constant. We present analytic results for D, F, and G states, and for a number of highly excited Rydberg states, with principal quantum numbers in the range 13≤n≤16, and orbital angular momenta l=n-2 and l=n-1. A closed-form analytic expression is derived for the contribution of high-energy photons, valid for any state with l≥2 and arbitrary n, l, and total angular momentum j. The low-energy contributions are written in the form of generalized Bethe logarithms and evaluated for selected states.

Mechanism for the Excited-State Multiple Proton Transfer Process of Dihydroxyanthraquinone Chromophores.

Science.gov (United States)

Zhou, Qiao; Du, Can; Yang, Li; Zhao, Meiyu; Dai, Yumei; Song, Peng

2017-06-22

The single and dual cooperated proton transfer dynamic process in the excited state of 1,5-dihydroxyanthraquinone (1,5-DHAQ) was theoretically investigated, taking solvent effects (ethanol) into account. The absorption and fluorescence spectra were simulated, and dual fluorescence exhibited, which is consistent with previous experiments. Analysis of the calculated IR and Raman vibration spectra reveals that the intramolecular hydrogen bonding interactions (O 20 -H 21 ···O 24 and O 22 -H 23 ···O 25 ) are strengthened following the excited proton transfer process. Finally, by constructing the potential energy surfaces of the ground state, first excited singlet state, and triplet state, the mechanism of the intramolecular proton transfer of 1,5-DHAQ can be revealed.

Equations of state for self-excited MHD generator studies

Energy Technology Data Exchange (ETDEWEB)

Rogers, F.J.; Ross, M.; Haggin, G.L.; Wong, L.K.

1980-02-26

We have constructed a state-of-the-art equation of state (EOS) for argon covering the temperature density range attainable by currently proposed self-excited MHD generators. The EOS for conditions in the flow channel was obtained primarily by a non-ideal plasma code (ACTEX) that is based on a many body activity expansion. For conditions in the driver chamber the EOS was primarily obtained from a fluid code (HDFP) that calculates the fluid properties from perturbation theory based on the insulator interatomic pair potential but including electronic excitations. The results are in agreement with several sets of experimental data in the 0.6 - 91 GPa pressure range.

Dynamics of second order in time evolution equations with state-dependent delay

Czech Academy of Sciences Publication Activity Database

Chueshov, I.; Rezunenko, Oleksandr

123-124, č. 1 (2015), s. 126-149 ISSN 0362-546X R&D Projects: GA ČR GAP103/12/2431 Institutional support: RVO:67985556 Keywords : Second order evolution equations * State dependent delay * Nonlinear plate * Finite-dimensional attractor Subject RIV: BD - Theory of Information Impact factor: 1.125, year: 2015 http://library.utia.cas.cz/separaty/2015/AS/rezunenko-0444708.pdf

The structure of nuclear states at low, intermediate and high excitation energies

International Nuclear Information System (INIS)

Soloviev, V.G.

1976-01-01

It is shown that within the model based on the quasiparticle-phonon interaction one can obtain the description of few-quasiparticle components of nuclear states at low, intermediate and high excitation energies. For the low-lying states the energy of each level is calculated. The few-quasiparticle components at intermediate and high excitation energies are represented to be averaged in certain energy intervals and their characteri stics are given as the corresponding strength functions. The fragmentation of single-particle states in deformed nuclei is studied. It is shown that in the distribution of the single-particle strength alongside with a large maximum there appear local maxima and the distribution itself has a long tail. The dependence of neutron strength functions on the excitation energy is investigated for the transfer reaction of the type (d,p) and (d,t). The s,- p,- and d-wave neutron strength functions are calculated at the neutron binding energy Bn. A satisfactory agreement with experiment is obtained. The energies and Elambda-strength functions for giant multipole resonances in deformed nuclei are calculated. The energies of giant quadrupole and octupole resonances are calculated. Their widths and fine structure are being studied. It is stated that to study the structure of highly excited states it is necessary to find the values of many-quasiparticle components of the wave functions. The ways of experimental determination of these components based on the study of γ-transitions between highly excited states are discussed

Kinetic studies following state-selective laser excitation: Progress report, March 15, 1988--March 14, 1989

International Nuclear Information System (INIS)

Keto, J.W.

1988-11-01

The objective of this contract is the study of state-to-state, electronic energy transfer reactions following two-photon laser excitation. We have chosen to study reactions of Xe 5p 5 np because of their relevance to the XeCl excimer laser. We are studying deactivation reactions in collisions with heavy atoms such as Ar, Kr, and Xe and reactive collisions with chlorides. The reactants are excited by multiphoton laser absorption. Product channels are observed by their fluorescence, or by laser induced fluorescence using a second color laser. Reaction rates are measured by observing the time dependent decay of signals from reactant and product channels. In addition we measure interaction potentials of the reactants by laser spectroscopy where the laser induced fluorescence or ionization is measured as a function of laser wavelength (excitation spectra) or by measuring fluorescence spectra at fixed laser frequencies with monochromators. The spectra are obtained in the form of either lineshapes or individual lines from rovibrational transitions of bound states. 11 refs. 4 figs., 3 tabs

New evolution equations for the joint response-excitation probability density function of stochastic solutions to first-order nonlinear PDEs

Science.gov (United States)

Venturi, D.; Karniadakis, G. E.

2012-08-01

By using functional integral methods we determine new evolution equations satisfied by the joint response-excitation probability density function (PDF) associated with the stochastic solution to first-order nonlinear partial differential equations (PDEs). The theory is presented for both fully nonlinear and for quasilinear scalar PDEs subject to random boundary conditions, random initial conditions or random forcing terms. Particular applications are discussed for the classical linear and nonlinear advection equations and for the advection-reaction equation. By using a Fourier-Galerkin spectral method we obtain numerical solutions of the proposed response-excitation PDF equations. These numerical solutions are compared against those obtained by using more conventional statistical approaches such as probabilistic collocation and multi-element probabilistic collocation methods. It is found that the response-excitation approach yields accurate predictions of the statistical properties of the system. In addition, it allows to directly ascertain the tails of probabilistic distributions, thus facilitating the assessment of rare events and associated risks. The computational cost of the response-excitation method is order magnitudes smaller than the one of more conventional statistical approaches if the PDE is subject to high-dimensional random boundary or initial conditions. The question of high-dimensionality for evolution equations involving multidimensional joint response-excitation PDFs is also addressed.

Ultra-high resolution spectroscopy of the He doubly excited states

International Nuclear Information System (INIS)

Bozek, J.D.; Schlachter, A.S.; Kaindl, G.; Schulz, K.

1995-11-01

Photoionization spectra of the doubly-excited states of He were measured using beamline 9.0.1 at the Advanced Light Source. The beamline utilizes a 4.5 m long 8 cm period undulator as its source together with a spherical grating monochromator to provide an extremely bright source of photons in the range of 20 - 300 eV. A resolving power (E/ΔE) of 64,000 was obtained from the 1 MeV FWEM (2p,3d) doubly excited state resonance of He at 64.12 eV. The high brightness of the source and the very high quality optical elements of the beamline were all essential for achieving such a high resolution. The beamline components and operation are described and spectra of the double excitation resonances of He presented

Neutral excitations in the Gaffnian state

Science.gov (United States)

Kang, Byungmin; Moore, Joel E.

2017-06-01

We study a model fractional quantum Hall (FQH) wave function called the Gaffnian state, which is believed to represent a gapless, strongly correlated state that is very different from conventional metals. To understand this exotic gapless state better, we provide a representation based on work of Halperin in which the pairing structure of the Gaffnian state becomes more explicit. We employ the single-mode approximation introduced by Girvin, MacDonald, and Platzman, here extended to three-body interactions, in order to treat a neutral collective excitation mode in order to clarify the physical origin of the gaplessness of the Gaffnian state. We discuss approaches to extract systematically the relevant physics in the long-distance, large-electron-number limit of FQH states using numerical calculations with relatively few electrons. In Appendices, we provide second-quantized expressions for many-body Haldane pseudopotentials in various geometries including the plane, sphere, cylinder, and torus based on the proper definition of the relative angular momentum.

Total photoionization cross-sections of excited electronic states by the algebraic diagrammatic construction-Stieltjes-Lanczos method.

Science.gov (United States)

Ruberti, M; Yun, R; Gokhberg, K; Kopelke, S; Cederbaum, L S; Tarantelli, F; Averbukh, V

2014-05-14

Here, we extend the L2 ab initio method for molecular photoionization cross-sections introduced in Gokhberg et al. [J. Chem. Phys. 130, 064104 (2009)] and benchmarked in Ruberti et al. [J. Chem. Phys. 139, 144107 (2013)] to the calculation of total photoionization cross-sections of molecules in electronically excited states. The method is based on the ab initio description of molecular electronic states within the many-electron Green's function approach, known as algebraic diagrammatic construction (ADC), and on the application of Stieltjes-Chebyshev moment theory to Lanczos pseudospectra of the ADC electronic Hamiltonian. The intermediate state representation of the dipole operator in the ADC basis is used to compute the transition moments between the excited states of the molecule. We compare the results obtained using different levels of the many-body theory, i.e., ADC(1), ADC(2), and ADC(2)x for the first two excited states of CO, N2, and H2O both at the ground state and the excited state equilibrium or saddle point geometries. We find that the single excitation ADC(1) method is not adequate even at the qualitative level and that the inclusion of double electronic excitations for description of excited state photoionization is essential. Moreover, we show that the use of the extended ADC(2)x method leads to a substantial systematic difference from the strictly second-order ADC(2). Our calculations demonstrate that a theoretical modelling of photoionization of excited states requires an intrinsically double excitation theory with respect to the ground state and cannot be achieved by the standard single excitation methods with the ground state as a reference.

Triplet Excited States as a Source of Relevant (Bio)Chemical Information

OpenAIRE

Jiménez Molero, María Consuelo; Miranda Alonso, Miguel Ángel

2014-01-01

The properties of triplet excited states are markedly medium-dependent, which turns this species into valuable tools for investigating the microenvironments existing in protein binding pockets. Monitoring of the triplet excited state behavior of drugs within transport proteins (serum albumins and alpha(1)-acid glycoproteins) by laser flash photolysis constitutes a valuable source of information on the strength of interaction, conformational freedom and protection from oxygen or other external...

The role of the excited electronic states in the C++H2O reaction

International Nuclear Information System (INIS)

Flores, Jesus R.; Gonzalez, Adan B.

2008-01-01

The electronic excited states of the [COH 2 ] + system have been studied in order to establish their role in the dynamics of the C + +H 2 O→[COH] + +H reaction, which is a prototypical ion-molecule reaction. The most relevant minima and saddle points of the lowest excited state have been determined and energy profiles for the lowest excited doublet and quartet electronic states have been computed along the fragmentation and isomerization coordinates. Also, nonadiabatic coupling strengths between the ground and the first excited state have been computed where they can be large. Our analysis suggests that the first excited state could play an important role in the generation of the formyl isomer, which has been detected in crossed beam experiments [D. M. Sonnenfroh et al., J. Chem. Phys. 83, 3985 (1985)], but could not be explained in quasiclassical trajectory computations [Y. Ishikawa et al., Chem. Phys. Lett. 370, 490 (2003); J. R. Flores, J. Chem. Phys. 125, 164309 (2006)

Bottom-up excited state dynamics of two cinnamate-based sunscreen filter molecules

OpenAIRE

Peperstraete, Yoann; Staniforth, Michael; Baker, Lewis A.; Rodrigues, Natércia D. N.; Cole-Filipiak, Neil C.; Quan, Wen-Dong; Stavros, Vasilios G.

2016-01-01

Methyl-E-4-methoxycinnamate (E-MMC) is a model chromophore of the commonly used commercial sunscreen agent, 2- ethylhexyl-E-4-methoxycinnamate (E-EHMC). In an effort to garner a molecular-level understanding of the photoprotection mechanisms in operation with E-EHMC, we have used time-resolved pump-probe spectroscopy to explore E-MMC’s and E-EHMC’s excited state dynamics upon UV-B photoexcitation to the S1 (11ππ*) state in both the gas- and solution-phase. In the gas-phase, our studies sugges...

The structure of low-lying states in ${}^{140}$Sm studied by Coulomb excitation

CERN Document Server

Klintefjord, M.; Görgen, A.; Bauer, C.; Bello Garrote, F.L.; Bönig, S.; Bounthong, B.; Damyanova, A.; Delaroche, J.P.; Fedosseev, V.; Fink, D.A.; Giacoppo, F.; Girod, M.; Hoff, P.; Imai, N.; Korten, W.; Larsen, A.C.; Libert, J.; Lutter, R.; Marsh, B.A.; Molkanov, P.L.; Naïdja, H.; Napiorkowski, P.; Nowacki, F.; Pakarinen, J.; Rapisarda, E.; Reiter, P.; Renstrøm, T.; Rothe, S.; Seliverstov, M.D.; Siebeck, B.; Siem, S.; Srebrny, J.; Stora, T.; Thöle, P.; Tornyi, T.G.; Tveten, G.M.; Van Duppen, P.; Vermeulen, M.J.; Voulot, D.; Warr, N.; Wenander, F.; De Witte, H.; Zielińska, M.

2016-05-02

The electromagnetic structure of $^{140}$Sm was studied in a low-energy Coulomb excitation experiment with a radioactive ion beam from the REX-ISOLDE facility at CERN. The $2^+$ and $4^+$ states of the ground-state band and a second $2^+$ state were populated by multi-step excitation. The analysis of the differential Coulomb excitation cross sections yielded reduced transition probabilities between all observed states and the spectroscopic quadrupole moment for the $2_1^+$ state. The experimental results are compared to large-scale shell model calculations and beyond-mean-field calculations based on the Gogny D1S interaction with a five-dimensional collective Hamiltonian formalism. Simpler geometric and algebraic models are also employed to interpret the experimental data. The results indicate that $^{140}$Sm shows considerable $\\gamma$ softness, but in contrast to earlier speculation no signs of shape coexistence at low excitation energy. This work sheds more light on the onset of deformation and collectivit...

Measurement of cross-sections for step-bystep excitation of inert gas atoms from metastable states by electron collisions

International Nuclear Information System (INIS)

Mityureva, A.A.; Penkin, N.P.; Smirnov, V.V.

1989-01-01

Excitation of argon atoms by electron collisions from metastable (MS) to high-lying states of inert gases (the so-called step-by-step excitation) is investigated. Formation of MS atoms m and their further step-by-step excitation up to k level is carried out by an electron beam with energy from 1 up to 40 eV. Time distribution of forming metastable and step-by-step electron collisions is used. The method used permits to measure the functions of step-by-step excitation and the absolute values of cross sections. Absolute values of cross-sections and functions of step-by-step excitation of some lines and argon levels are obtained

Effects of crossed states on photoluminescence excitation spectroscopy of InAs quantum dots

Directory of Open Access Journals (Sweden)

Lin Chien-Hung

2011-01-01

Full Text Available Abstract In this report, the influence of the intrinsic transitions between bound-to-delocalized states (crossed states or quasicontinuous density of electron-hole states on photoluminescence excitation (PLE spectra of InAs quantum dots (QDs was investigated. The InAs QDs were different in size, shape, and number of bound states. Results from the PLE spectroscopy at low temperature and under a high magnetic field (up to 14 T were compared. Our findings show that the profile of the PLE resonances associated with the bound transitions disintegrated and broadened. This was attributed to the coupling of the localized QD excited states to the crossed states and scattering of longitudinal acoustical (LA phonons. The degree of spectral linewidth broadening was larger for the excited state in smaller QDs because of the higher crossed joint density of states and scattering rate.

Factorizing the time evolution operator

International Nuclear Information System (INIS)

Garcia Quijas, P C; Arevalo Aguilar, L M

2007-01-01

There is a widespread belief in the quantum physical community, and textbooks used to teach quantum mechanics, that it is a difficult task to apply the time evolution operator e itH-hat/h on an initial wavefunction. Because the Hamiltonian operator is, generally, the sum of two operators, then it is not possible to apply the time evolution operator on an initial wavefunction ψ(x, 0), for it implies using terms like (a-hat + b-hat). A possible solution is to factorize the time evolution operator and then apply successively the individual exponential operator on the initial wavefunction. However, the exponential operator does not directly factorize, i.e. e a-hat+b-hat ≠ e a-hat e b-hat . In this study we present a useful procedure for factorizing the time evolution operator when the argument of the exponential is a sum of two operators, which obey specific commutation relations. Then, we apply the exponential operator as an evolution operator for the case of elementary unidimensional potentials, like a particle subject to a constant force and a harmonic oscillator. Also, we discuss an apparent paradox concerning the time evolution operator and non-spreading wave packets addressed previously in the literature

Photoresponse of 60Ni below 10-MeV excitation energy: Evolution of dipole resonances in fp-shell nuclei near N=Z

Science.gov (United States)

Scheck, M.; Ponomarev, V. Yu.; Fritzsche, M.; Joubert, J.; Aumann, T.; Beller, J.; Isaak, J.; Kelley, J. H.; Kwan, E.; Pietralla, N.; Raut, R.; Romig, C.; Rusev, G.; Savran, D.; Schorrenberger, L.; Sonnabend, K.; Tonchev, A. P.; Tornow, W.; Weller, H. R.; Zilges, A.; Zweidinger, M.

2013-10-01

Background: Within the last decade, below the giant dipole resonance the existence of a concentration of additional electric dipole strength has been established. This accumulation of low-lying E1 strength is commonly referred to as pygmy dipole resonance (PDR).Purpose: The photoresponse of 60Ni has been investigated experimentally and theoretically to test the evolution of the PDR in a nucleus with only a small neutron excess. Furthermore, the isoscalar and isovector M1 resonances were investigated.Method: Spin-1 states were excited by exploiting the (γ,γ') nuclear resonance fluorescence technique with unpolarized continuous bremsstrahlung as well as with fully linearly polarized, quasimonochromatic, Compton-backscattered laser photons in the entrance channel of the reaction.Results: Up to 10 MeV a detailed picture of J=1 levels was obtained. For the preponderant number of the individual levels spin and parity were firmly assigned. Furthermore, branching ratios, transition widths, and reduced B(E1) or B(M1) excitation probability were calculated from the measured scattering cross sections. A comparison with theoretical results obtained within the quasiparticle phonon model allows an insight into the microscopic structure of the observed states.Conclusions: Below 10 MeV the directly observed E1 strength [∑B(E1)↑=(153.8±9.5) e2(fm)2] exhausts 0.5% of the Thomas-Reiche-Kuhn sum rule. This value increases to 0.8% of the sum rule [∑B(E1)↑=(250.9±31.1) e2(fm)2] when indirectly observed branches to lower-lying levels are considered. Two accumulations of M1 excited spin-1 states near 8 and 9 MeV excitation energy are identified as isoscalar and isovector M1 resonances dominated by proton and neutron f7/2→f5/2 spin-flip excitations. The B(M1)↑ strength of these structures accumulates to 3.94(27)μN2.

Excited states of 12C above the alpha-decay threshold

International Nuclear Information System (INIS)

Freer, M; Ashwood, N I; Barr, M; Curtis, N; Malcolm, J D; Wheldon, C; Ziman, V A; Almaraz-Calderon, S; Aprahamian, A; Bucher, B; Couder, M; Fang, X; Jung, F; Lu, W; Roberts, A; Tan, W P; Copp, P; Lesher, S

2011-01-01

The excitation energy spectrum of 12 C is important for both structural and astrophysical reasons; here we present evidence for a new state in 12 C. The two reactions 12 C( 4 He, 4 He+ 4 He+ 4 He) 4 He and 9 Be( 4 He, 4 He+ 4 He+ 4 He)n were measured using an array of four double sided strip detectors. Excited states in 12 C were reconstructed filtered by the condition that the alpha-decay proceeded via the 8 Be ground-state. In both measurements evidence was found for a new state at 13.3(0.2) MeV with a width 1.7(0.2) MeV. Angular correlation measurements from the 12 C( 4 He, 4 He+ 4 He+ 4 He) 4 He reaction indicates that the state may have J π = 4 + .

Calculation of neutral beam deposition accounting for excited states

International Nuclear Information System (INIS)

Gianakon, T.A.

1992-09-01

Large-scale neutral-beam auxillary heating of plasmas has led to new plasma operational regimes which are often dominated by fast ions injected via the absorption of an energetic beam of hydrogen neutrals. An accurate simulation of the slowing down and transport of these fast ions requires an intimate knowledge of the hydrogenic neutral deposition on each flux surface of the plasma. As a refinement to the present generation of transport codes, which base their beam deposition on ground-state reaction rates, a new set of routines, based on the excited states of hydrogen, is presented as mechanism for computing the attenuation and deposition of a beam of energetic neutrals. Additionally, the numerical formulations for the underlying atomic physics for hydrogen impacting on the constiuent plasma species is developed and compiled as a numerical database. Sample results based on this excited state model are compared with the ground-state model for simple plasma configurations

Dark excited states of carotenoids: Consensus and controversy

Czech Academy of Sciences Publication Activity Database

Polívka, Tomáš; Sundström, V.

2009-01-01

Roč. 477, 1-3 (2009), s. 1-11 ISSN 0009-2614 Institutional research plan: CEZ:AV0Z50510513 Keywords : carotenoids * excited states * relaxation pathways * femtosecond spectroscopy Subject RIV: BO - Biophysics Impact factor: 2.291, year: 2009

The Rapid Evolution of the Exciting Star of the Stingray Nebula

Science.gov (United States)

Reindl, N.; Rauch, T.; Parthasarathy, M.; Werner, K.; Kruk, J.W.; Hamann, W. R.; Sander, A.; Todt, H.

2014-01-01

Context: SAO244567, the exciting star of the Stingray nebula, is rapidly evolving. Previous analyses suggested that it has heated up from an effective temperature of about 21 kK in 1971 to over 50 kK in the 1990s. Canonical post-asymptotic giant branch evolution suggests a relatively high mass while previous analyses indicate a low-mass star. Aims: A comprehensive model-atmosphere analysis of UV and optical spectra taken during 1988-2006 should reveal the detailed temporal evolution of its atmospheric parameters and provide explanations for the unusually fast evolution. Methods: Fitting line profiles from static and expanding non-LTE model atmospheres to the observed spectra allowed us to study the temporal change of effective temperature, surface gravity, mass-loss rate, and terminal wind velocity. In addition, we determined the chemical composition of the atmosphere. Results: We find that the central star has steadily increased its effective temperature from 38 kK in 1988 to a peak value of 60 kK in 2002. During the same time, the star was contracting, as concluded from an increase in surface gravity from log g = 4.8 to 6.0 and a drop in luminosity. Simultaneously, the mass-loss rate declined from log(M/M (solar mass) yr (exp -1)) = -9.0 to -11.6 and the terminal wind velocity increased from v (infinity) = 1800 km s (exp -1) to 2800 km s (exp -1). Since around 2002, the star stopped heating and has cooled down again to 55 kK by 2006. It has a largely solar surface composition with the exception of slightly subsolar carbon, phosphorus, and sulfur. The results are discussed by considering different evolutionary scenarios. Conclusions: The position of SAO244567 in the log T (sub eff) -log g plane places the star in the region of sdO stars. By comparison with stellar-evolution calculations, we confirm that SAO244567 must be a low-mass star (M nebula with a kinematical age of only about 1000 years. We speculate that the star could be a late He-shell flash object

Measured lifetimes of states in 197Au and a critical comparison with the weak-coupling core-excitation model

International Nuclear Information System (INIS)

Bolotin, H.H.; Kennedy, D.L.; Linard, B.J.; Stuchbery, A.E.

1979-01-01

The lifetimes of five excited states in 197 Au up to an excitation energy of 885 keV were measured by the recoil-distance method (RDM). These levels were populated by Coulomb excitation using both 90 MeV 20 Ne and 120 MeV 35 Cl ion beams. The experimentally determined spectroscopy of the low-lying levels 3/2 + (ground state) and 1/2 + , (3/2) + 2 , 5/2 + and 7/2 + at 77.3, 268.8, 278.9, and 547.5 keV excitation energy, respectively, has been critically compared with the detailed predictions of the de-Shalit weak-coupling core-excitation model. When the model is taken to represent the case of a dsub(3/2) proton hole coupled to a 198 Hg core, the model parameters obtained are in accord with the criteria implicit for weak core coupling and, at the same time, are in remarkably good agreement with virtually all measured E2 and M1 transition rates. (Auth.)

Evidence for excited state intramolecular charge transfer in benzazole-based pseudo-stilbenes.

Science.gov (United States)

Santos, Fabiano da Silveira; Descalzo, Rodrigo Roceti; Gonçalves, Paulo Fernando Bruno; Benvenutti, Edilson Valmir; Rodembusch, Fabiano Severo

2012-08-21

Two azo compounds were obtained through the diazotization reaction of aminobenzazole derivatives and N,N-dimethylaniline using clay montmorillonite KSF as catalyst. The synthesized dyes were characterized using elemental analysis, Fourier transform infrared spectroscopy, and (13)C and (1)H NMR spectroscopy in solution. Their photophysical behavior was studied using UV-vis and steady-state fluorescence in solution. These dyes present intense absorption in the blue region. The spectral features of the azo compounds can be related to the pseudo-stilbene type as well as the E isomer of the dyes. Excitation at the absorption maxima does not produce emissive species in the excited state. However, excitation around 350 nm allowed dual emission of fluorescence, from both a locally excited (LE, short wavelength) and an intramolecular charge transfer (ICT, long wavelength) state, which was corroborated by a linear relation of the fluorescence maximum (ν(max)) versus the solvent polarity function (Δf) from the Lippert-Mataga correlation. Evidence of TICT in these dyes was discussed from the viscosity dependence of the fluorescence intensity in the ICT emission band. Theoretical calculations were also performed in order to study the geometry and charge distribution of the dyes in their ground and excited electronic states. Using DFT methods at the theoretical levels BLYP/Aug-cc-pVDZ, for geometry optimizations and frequency calculations, and B3LYP/6-311+G(2d), for single-point energy evaluations, the calculations revealed that the least energetic and most intense photon absorption leads to a very polar excited state that relaxes non-radioactively, which can be associated with photochemical isomerization.

On the truncation of the number of excited states in density functional theory sum-over-states calculations of indirect spin spin coupling constants

International Nuclear Information System (INIS)

Zarycz, M. Natalia C.; Provasi, Patricio F.; Sauer, Stephan P. A.

2015-01-01

It is investigated, whether the number of excited (pseudo)states can be truncated in the sum-over-states expression for indirect spin-spin coupling constants (SSCCs), which is used in the Contributions from Localized Orbitals within the Polarization Propagator Approach and Inner Projections of the Polarization Propagator (IPPP-CLOPPA) approach to analyzing SSCCs in terms of localized orbitals. As a test set we have studied the nine simple compounds, CH 4 , NH 3 , H 2 O, SiH 4 , PH 3 , SH 2 , C 2 H 2 , C 2 H 4 , and C 2 H 6 . The excited (pseudo)states were obtained from time-dependent density functional theory (TD-DFT) calculations with the B3LYP exchange-correlation functional and the specialized core-property basis set, aug-cc-pVTZ-J. We investigated both how the calculated coupling constants depend on the number of (pseudo)states included in the summation and whether the summation can be truncated in a systematic way at a smaller number of states and extrapolated to the total number of (pseudo)states for the given one-electron basis set. We find that this is possible and that for some of the couplings it is sufficient to include only about 30% of the excited (pseudo)states

Selective two-photon excitation of a vibronic state by correlated photons.

Science.gov (United States)

Oka, Hisaki

2011-03-28

We theoretically investigate the two-photon excitation of a molecular vibronic state by correlated photons with energy anticorrelation. A Morse oscillator having three sets of vibronic states is used, as an example, to evaluate the selectivity and efficiency of two-photon excitation. We show that a vibrational mode can be selectively excited with high efficiency by the correlated photons, without phase manipulation or pulse-shaping techniques. This can be achieved by controlling the quantum correlation so that the photon pair concurrently has two pulse widths, namely, a temporally narrow width and a spectrally narrow width. Though this concurrence is seemingly contradictory, we can create such a photon pair by tailoring the quantum correlation between two photons.

Amplitudes and state parameters from ion- and atom-atom excitation processes

International Nuclear Information System (INIS)

Andersen, T.; Horsdal-Pedersen, E.

1984-01-01

This chapter examines single collisions between two atomic species, one of which is initially in a 1 S state (there is only one initial spin channel). The collisions are characterized by a definite scattering plane and a definite orientation. Topics considered include an angular correlation between scattered particles and autoionization electrons or polarized photons emitted from states excited in atomic collisions (photon emission, electron emission, selectivity excited target atoms), experimental methods for obtaining information on the alignment and orientation parameters of atoms or ions excited in specific collisions, results of experiments and numerical calculations (quasi-oneelectron systems, He + -He collisions, other collision systems), and future aspects and possible applications of the polarizedphoton, scattered-particle coincidence techniques to atomic spectroscopy

Evolutional Properties of Localized Excitations for Generalized Broer-Kaup System in (2+1) Dimensions

International Nuclear Information System (INIS)

Zheng Chunlong; Ye Jianfeng; Xu Yuan

2006-01-01

Using a special Painleve-Baecklund transformation as well as the extended mapping approach and the linear superposition theorem, we obtain new families of variable separation solutions to the (2+1)-dimensional generalized Broer-Kaup (GBK) system. Based on the derived exact solution, we reveal some novel evolutional behaviors of localized excitations, i.e. fission and fusion phenomena in the (2+1)-dimensional GBK system.

Entanglement between electronic states in silicene and photons

Energy Technology Data Exchange (ETDEWEB)

Rastgoo, S. [Physics Department, College of Sciences, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of); Shirkani, H. [Physics Department, Persian Gulf University, Bushehr 75169 (Iran, Islamic Republic of); Golshan, M.M., E-mail: golshan@susc.ac.ir [Physics Department, College of Sciences, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of)

2015-06-12

Temporal behavior of entanglement between electrons in silicene and single mode radiations is reported. We show that the corresponding total Hamiltonian and time evolution operators are block diagonal. Initial states are divided into two categories for which buckling and the intrinsic spin–orbit effects are either of opposite or the same signs. Negativity shows that π-electrons and photons periodically become entangled for both categories. The entanglement spontaneously shows abrupt variations when buckling and the spin–orbit effects are equal but opposite in sign, leading to quantum phase transitions. As photonic excitations increase, the entanglement exhibits plateaus of constant durations for such initial states. - Highlights: • Time evolution of entanglement between π-electrons and photons in silicene is reported. • Intrinsic spin–orbit coupling (ISOC) and buckling effect (BE) are taken into account. • Initial states with ISOC and BE of opposite signs show quantum phase transitions. • Quantum phase transitions spontaneously occur when ISOC is equal to BE. • Periodic plateaus of maximal entanglement are observed for high photonic excitations.

Excitations in superfluid systems: contributions of the nuclear structure; Excitations dans les systemes superfluides: contributions de la structure nucleaire

Energy Technology Data Exchange (ETDEWEB)

Khan, E

2005-12-15

The author presents successively the theoretical aspect, the experimental aspect and the applied aspect of excitations in nuclear structures. The quasi-particle random phase approximation (QRPA) tool is first described. Recent approaches on QRPA are based on the theory of the density function where the ground state and excited states are described from the same nucleon-nucleon interaction. 2 methods for measuring the collective excitations are then presented: the proton scattering that has the potentiality to investigate the evolution of magicity, the second method is in fact a new method for measuring the giant mono-polar resonance (GMP) in exotic nuclei. Nuclear reactions are considered as a compulsory step on the way from observables like cross-sections to nuclear structure. The author highlights the assets of the convolution model that can generate the optical potential from the effective nucleon-nucleon interaction and from proton and neutron densities of the nuclei involved. R-processes in nucleosynthesis and neutron stars are reviewed as applications of collective excitations in the field of nuclear astrophysics. (A.C.)

Quantum communication and state transfer in spin chains

International Nuclear Information System (INIS)

Van der Jeugt, Joris

2011-01-01

We investigate the time evolution of a single spin excitation state in certain linear spin chains, as a model for quantum communication. We consider first the simplest possible spin chain, where the spin chain data (the nearest neighbour interaction strengths and the magnetic field strengths) are constant throughout the chain. The time evolution of a single spin state is determined, and this time evolution is illustrated by means of an animation. Some years ago it was discovered that when the spin chain data are of a special form so-called perfect state transfer takes place. These special spin chain data can be linked to the Jacobi matrix entries of Krawtchouk polynomials or dual Hahn polynomials. We discuss here the case related to Krawtchouk polynomials, and illustrate the possibility of perfect state transfer by an animation showing the time evolution of the spin chain from an initial single spin state. Very recently, these ideas were extended to discrete orthogonal polynomials of q-hypergeometric type. Here, a remarkable result is a new analytic model where perfect state transfer is achieved: this is when the spin chain data are related to the Jacobi matrix of q-Krawtchouk polynomials. This case is discussed here, and again illustrated by means of an animation.

Effects of ligand substitution on the excited state dynamics of the Ru(dcbpy)(CO){sub 2}I{sub 2} complex

Energy Technology Data Exchange (ETDEWEB)

Lehtovuori, Viivi; Kallioinen, Jani; Myllyperkioe, Pasi; Haukka, Matti; Korppi-Tommola, Jouko

2003-11-15

Spectroscopic evidence suggest [PCCP 3 (2001) 1992] that illumination with visible light of the [trans-I-Ru(dcbpy)(CO){sub 2}I{sub 2}] (dcbpy4,4{sup '}-dicarboxy-2,2{sup '}-bipyridine) complex in solution induces dissociation of a CO group followed by reorganization of the ligands and attachment of a solvent molecule. In the present study, we report results on excited state dynamics of this ruthenium complex and its photoproduct. Femtosecond transient absorption measurements reveal dominance of excited state absorption of the reactant and the photoproduct [cis-I-Ru(dcbpy)(CO)(Sol)I{sub 2}] (Sol=ethanol or acetonitrile) in the visible spectral region. The time-resolved measurements for the reactant at 77 K indicate interligand charge transfer from mixed Ru-I states to empty dcbpy orbitals. For the photoproduct, no such transfer was observed. In both complexes recovery from the lowest energy excited triplet state to the ground state occurs via two channels: radiative relaxation and a parallel barrier controlled non-radiative relaxation. The barrier is much higher in the reactant (about 850 cm{sup -1}) than in the product. A combination of DFT and ZINDO/CI calculations was used to estimate excited singlet and triplet spectra of the reactant and the product molecules. Calculated singlet-triplet difference spectra qualitatively match the observed transient spectra 500 fs after excitation supporting the idea that observed excited state relaxation occurs from the triplet states in both complexes.

Lifetime measurements of excited states in 17C: Possible interplay between collectivity and halo effects

International Nuclear Information System (INIS)

Suzuki, D.; Iwasaki, H.; Ong, H.J.; Imai, N.; Sakurai, H.; Nakao, T.; Aoi, N.; Baba, H.; Bishop, S.; Ichikawa, Y.; Ishihara, M.; Kondo, Y.; Kubo, T.; Kurita, K.; Motobayashi, T.; Nakamura, T.; Okumura, T.; Onishi, T.K.; Ota, S.; Suzuki, M.K.

2008-01-01

Lifetime measurements were performed on low-lying excited states of the neutron-rich isotope 17 C using the recoil shadow method. The γ-decay mean lifetimes were determined to be 583±21(stat)±35(syst) ps for the first excited state at 212 keV and 18.9±0.6(stat)±4.7(syst) ps for the second excited state at 333 keV. Based on a comparison with the empirical upper limits for the electromagnetic transition strengths, these decays are concluded to be predominantly M1 transitions. The reduced M1 transition probabilities to the ground state were deduced to be (1.0±0.1)x10 -2 μ N 2 and (8.2 -1.8 +3.2 )x10 -2 μ N 2 , respectively, for the first and second excited states. The strongly hindered M1 strength as well as the lowered excitation energy represents unique nature of the 212-keV state

Dependence of Excited State Potential Energy Surfaces on the Spatial Overlap of the Kohn-Sham Orbitals and the Amount of Nonlocal Hartree-Fock Exchange in Time-Dependent Density Functional Theory.

Science.gov (United States)

Plötner, Jürgen; Tozer, David J; Dreuw, Andreas

2010-08-10

Time-dependent density functional theory (TDDFT) with standard GGA or hybrid exchange-correlation functionals is not capable of describing the potential energy surface of the S1 state of Pigment Yellow 101 correctly; an additional local minimum is observed at a twisted geometry with substantial charge transfer (CT) character. To investigate the influence of nonlocal exact orbital (Hartree-Fock) exchange on the shape of the potential energy surface of the S1 state in detail, it has been computed along the twisting coordinate employing the standard BP86, B3LYP, and BHLYP xc-functionals as well as the long-range separated (LRS) exchange-correlation (xc)-functionals LC-BOP, ωB97X, ωPBE, and CAM-B3LYP and compared to RI-CC2 benchmark results. Additionally, a recently suggested Λ-parameter has been employed that measures the amount of CT in an excited state by calculating the spatial overlap of the occupied and virtual molecular orbitals involved in the transition. Here, the error in the calculated S1 potential energy curves at BP86, B3LYP, and BHLYP can be clearly related to the Λ-parameter, i.e., to the extent of charge transfer. Additionally, it is demonstrated that the CT problem is largely alleviated when the BHLYP xc-functional is employed, although it still exhibits a weak tendency to underestimate the energy of CT states. The situation improves drastically when LRS-functionals are employed within TDDFT excited state calculations. All tested LRS-functionals give qualitatively the correct potential energy curves of the energetically lowest excited states of P. Y. 101 along the twisting coordinate. While LC-BOP and ωB97X overcorrect the CT problem and now tend to give too large excitation energies compared to other non-CT states, ωPBE and CAM-B3LYP are in excellent agreement with the RI-CC2 results, with respect to both the correct shape of the potential energy curve as well as the absolute values of the calculated excitation energies.

QM/MM studies on the excited-state relaxation mechanism of a semisynthetic dTPT3 base.

Science.gov (United States)

Guo, Wei-Wei; Zhang, Teng-Shuo; Fang, Wei-Hai; Cui, Ganglong

2018-02-14

Semisynthetic alphabets can potentially increase the genetic information stored in DNA through the formation of unusual base pairs. Recent experiments have shown that near-visible-light irradiation of the dTPT3 chromophore could lead to the formation of a reactive triplet state and of singlet oxygen in high quantum yields. However, the detailed excited-state relaxation paths that populate the lowest triplet state are unclear. Herein, we have for the first time employed the QM(MS-CASPT2//CASSCF)/MM method to explore the spectroscopic properties and excited-state relaxation mechanism of the aqueous dTPT3 chromophore. On the basis of the results, we have found that (1) the S 2 ( 1 ππ*) state of dTPT3 is the initially populated excited singlet state upon near-visible light irradiation; and (2) there are two efficient relaxation pathways to populate the lowest triplet state, i.e. T 1 ( 3 ππ*). In the first one, the S 2 ( 1 ππ*) system first decays to the S 1 ( 1 nπ*) state near the S 2 /S 1 conical intersection, which is followed by an efficient S 1 → T 1 intersystem crossing process at the S 1 /T 1 crossing point; in the second one, an efficient S 2 → T 2 intersystem crossing takes place first, and then, the T 2 ( 3 nπ*) system hops to the T 1 ( 3 ππ*) state through an internal conversion process at the T 2 /T 1 conical intersection. Moreover, an S 2 /S 1 /T 2 intersection region is found to play a vital role in the excited-state relaxation. These new mechanistic insights help in understanding the photophysics and photochemistry of unusual base pairs.

General active space commutator-based coupled cluster theory of general excitation rank for electronically excited states: implementation and application to ScH.

Science.gov (United States)

Hubert, Mickaël; Olsen, Jeppe; Loras, Jessica; Fleig, Timo

2013-11-21

We present a new implementation of general excitation rank coupled cluster theory for electronically excited states based on the single-reference multi-reference formalism. The method may include active-space selected and/or general higher excitations by means of the general active space concept. It may employ molecular integrals over the four-component Lévy-Leblond Hamiltonian or the relativistic spin-orbit-free four-component Hamiltonian of Dyall. In an initial application to ground- and excited states of the scandium monohydride molecule we report spectroscopic constants using basis sets of up to quadruple-zeta quality and up to full iterative triple excitations in the cluster operators. Effects due to spin-orbit interaction are evaluated using two-component multi-reference configuration interaction for assessing the accuracy of the coupled cluster results.

Concluding remarks of international symposium on highly excited states in nuclear reactions

Energy Technology Data Exchange (ETDEWEB)

Bernstein, A. M.; Ikegami, H.; Muraoka, M. [eds.

1980-01-01

This is the concluding remarks in the international symposium on highly excited states in nuclear reactions. The remarks concentrate on the giant quadrupole states. In the framework of the distorted wave Born approximation (DWB), the differential cross section can be deduced. The relevant transition matrix elements are defined, and the quantities which are measured in inelastic hadron (h, h') reactions are shown. These are used to obtain both neutron and proton transition multipole matrix elements. This is equivalent to make the isospin decomposition of the electromagnetic transition matrix elements. The ratios of the transition matrix elements of neutrons and protons of the lowest 2/sup +/ states in even-even single closed shell nuclei are evaluated and compared with experimental results. For each nucleus, the consistency between various measurements is generally good. The effect of the virtual excitation of giant 2/sup +/ states into the ground and first excited states of even-even nuclei is discussed. The accuracy of (h, h') results can be tested.

On satellite lines anomalies in OH excited states

International Nuclear Information System (INIS)

Elitzur, M.

1976-01-01

It is argued that different pumps produce similar distributions of populations in the first two excited states of OH. The pattern observed recently in G 219.3 - 07 by Whiteoak and Gardner can be due either to radiative or collisional pump. (author)

Calculations of core-excited states in Li

International Nuclear Information System (INIS)

Verbockhaven, G.; Hansen, J.E.

1999-01-01

We report on progress in the calculation of three-electron states making use of B-spline basis sets. In particular we discuss the advantages and disadvantages of using a Hartree-Fock basis (expanded in B-splines) compared to the use of hydrogenic basis states. Preliminary results are presented for the 2 S terms in Li below the 1s2s 3 S limit at 64.4 eV. The 2 S terms have been studied less extensively than other core-excited states in Li. In this particular case the choice of basis has a large influence on the quality of the results. (orig.)

The population transfer of high excited states of Rydberg lithium atoms in a microwave field

International Nuclear Information System (INIS)

Jiang Lijuan; Zhang Xianzhou; Ma Huanqiang; Jia Guangrui; Zhang Yonghui; Xia Lihua

2012-01-01

Using the time-dependent multilevel approach (TDMA), the properties of high excited Rydberg lithium atom have been obtained in the microwave field. The population transfer of lithium atom are studied on numerical calculation, quantum states are controlled and manipulated by microwave field. It shows that the population can be completely transferred to the target state by changing the chirped rate and field amplitude. (authors)

Coulomb Excitation of Neutron Deficient Sn-Isotopes using REX-ISOLDE

CERN Multimedia

Di julio, D D; Kownacki, J M; Marechal, F; Andreoiu, C; Siem, S; Perrot, F; Van duppen, P L E; Napiorkowski, P J; Iwanicki, J S

2002-01-01

It is proposed to study the evolution of the reduced transition probabilities, B(E2; 0$^{+} \\rightarrow$ 2$^{+}$), for neutron deficient Sn isotopes by Coulomb excitation in inverse kinematics using REX-ISOLDE and the MINIBALL detector array. Measurements of the reduced transition matrix element for the transition between the ground state and the first excited 2$^{+}$ state in light even-even Sn isotopes provide a means to study e.g. core polarization effects in the $^{100}$Sn core. Previous attempts to measure this quantity have been carried out using the decay of isomeric states populated in fusion evaporation reactions. We thus propose to utilize the unique opportunity provided by REX-ISOLDE, after the energy upgrade to 3.1 MeV/u, to use the more model-independent approach of Coulomb excitation to measure this quantity in a number of isotopes in this region.

Electronic Structure and Excited-State Dynamics of an Arduengo-Type Carbene and its Imidazolone Oxidation Product.

Science.gov (United States)

Schmitt, Hans-Christian; Flock, Marco; Welz, Eileen; Engels, Bernd; Schneider, Heidi; Radius, Udo; Fischer, Ingo

2017-03-02

We describe an investigation of the excited-state dynamics of isolated 1,3-di-tert-butyl-imidazoline-2-ylidene (tBu 2 Im, C 11 H 20 N 2 , m/z=180), an Arduengo-type carbene, by time- and frequency-resolved photoionization using a picosecond laser system. The energies of several singlet and triplet excited states were calculated by time-dependent density functional theory (TD-DFT). The S 1 state of the carbene deactivates on a 100 ps time scale possibly by intersystem crossing. In the experiments we observed an additional signal at m/z=196, that was assigned to the oxidation product 1,3-di-tert-butyl-imidazolone, tBu 2 ImO. It shows a well-resolved resonance-enhanced multiphoton ionization (REMPI) spectrum with an origin located at 36951 cm -1 . Several low-lying vibrational bands could be assigned, with a lifetime that depends strongly on the excitation energy. At the origin the lifetime is longer than 3 ns, but drops to 49 ps at higher excess energies. To confirm formation of the imidazolone we also performed experiments on benzimidazolone (BzImO) for comparison. Apart from a redshift for BzImO the spectra of the two compounds are very similar. The TD-DFT values display a very good agreement with the experimental data. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Exact finite volume expectation values of local operators in excited states

Energy Technology Data Exchange (ETDEWEB)

Pozsgay, B. [MTA-BME “Momentum” Statistical Field Theory Research Group,Budafoki út 8, 1111 Budapest (Hungary); Szécsényi, I.M. [Department of Mathematical Sciences, Durham University, South Road, Durham, DH1 3LE (United Kingdom); Institute of Theoretical Physics, Eötvös Loránd University,Pázmány Péter sétány 1/A, 1117 Budapest (Hungary); Takács, G. [MTA-BME “Momentum” Statistical Field Theory Research Group,Budafoki út 8, 1111 Budapest (Hungary); Department of Theoretical Physics, Budapest University of Technology and Economics,Budafoki út 8, 1111 Budapest (Hungary)

2015-04-07

We present a conjecture for the exact expression of finite volume expectation values in excited states in integrable quantum field theories, which is an extension of an earlier conjecture to the case of general diagonal factorized scattering with bound states and a nontrivial bootstrap structure. The conjectured expression is a spectral expansion which uses the exact form factors and the excited state thermodynamic Bethe Ansatz as building blocks. The conjecture is proven for the case of the trace of the energy-moment tensor. Concerning its validity for more general operators, we provide numerical evidence using the truncated conformal space approach. It is found that the expansion fails to be well-defined for small values of the volume in cases when the singularity structure of the TBA equations undergoes a non-trivial rearrangement under some critical value of the volume. Despite these shortcomings, the conjectured expression is expected to be valid for all volumes for most of the excited states, and as an expansion above the critical volume for the rest.

Exact finite volume expectation values of local operators in excited states

International Nuclear Information System (INIS)

Pozsgay, B.; Szécsényi, I.M.; Takács, G.

2015-01-01

We present a conjecture for the exact expression of finite volume expectation values in excited states in integrable quantum field theories, which is an extension of an earlier conjecture to the case of general diagonal factorized scattering with bound states and a nontrivial bootstrap structure. The conjectured expression is a spectral expansion which uses the exact form factors and the excited state thermodynamic Bethe Ansatz as building blocks. The conjecture is proven for the case of the trace of the energy-moment tensor. Concerning its validity for more general operators, we provide numerical evidence using the truncated conformal space approach. It is found that the expansion fails to be well-defined for small values of the volume in cases when the singularity structure of the TBA equations undergoes a non-trivial rearrangement under some critical value of the volume. Despite these shortcomings, the conjectured expression is expected to be valid for all volumes for most of the excited states, and as an expansion above the critical volume for the rest.

Formation of excited states in high-Z helium-like systems

International Nuclear Information System (INIS)

Fritzsche, S.; Fricke, B.; Brinzanescu, O.

1999-12-01

High-Z helium-like ions represent the simplest multi-electron systems for studying the interplay between electron-electron correlations, relativistic as well as quantum electrodynamical effects in strong fields. In contrast to the adjacent lithium-like ions, however, almost no experimental information is available about the excited states in the high-Z domain of the helium sequence. Here, we present a theoretical analysis of the X-ray production and decay dynamics of the excited states in helium-like uranium. Emphasize has been paid particularly to the formation of the 3 P 0 and 3 P 2 levels by using electron capture into hydrogen-like U 91+ . Both states are of interest for precise measurements on high-Z helium-like ions in the future. (orig.)

Direct Electron Impact Excitation of Rydberg-Valence States of Molecular Nitrogen

Science.gov (United States)

Malone, C. P.; Johnson, P. V.; Liu, X.; Ajdari, B.; Muleady, S.; Kanik, I.; Khakoo, M. A.

2012-12-01

Collisions between electrons and neutral N2 molecules result in emissions that provide an important diagnostic probe for understanding the ionospheric energy balance and the effects of space weather in upper atmospheres. Also, transitions to singlet ungerade states cause N2 to be a strong absorber of solar radiation in the EUV spectral range where many ro-vibrational levels of these Rydberg-valence (RV) states are predissociative. Thus, their respective excitation and emission cross sections are important parameters for understanding the [N]/[N2] ratio in the thermosphere of nitrogen dominated atmospheres. The following work provides improved constraints on absolute and relative excitation cross sections of numerous RV states of N2, enabling more physically accurate atmospheric modeling. Here, we present recent integral cross sections (ICSs) for electron impact excitation of RV states of N2 [6], which were based on the differential cross sections (DCSs) derived from electron energy-loss (EEL) spectra of [5]. This work resulted in electronic excitation cross sections over the following measured vibrational levels: b 1Πu (v‧=0-14), c3 1Πu (v‧=0-3), o3 1Πu (v‧=0-3), b‧ 1Σu+ (v‧=0-10), c‧4 1Σu+ (v‧=0-3), G 3Πu (v‧=0-3), and F 3Πu (v‧=0-3). We further adjusted the cross sections of the RV states by extending the vibronic contributions to unmeasured v‧-levels via the relative excitation probabilities (REPs) as discussed in [6]. This resulted in REP-scaled ICSs over the following vibrational levels for the singlet ungerade states: b(0-19), c3(0-4), o3(0-4), b‧(0-16), and c‧4(0-8). Comparison of the ICSs of [6] with available EEL based measurements, theoretical calculations, and emission based work generally shows good agreement within error estimations, except with the recent reevaluation provided by [1]. Further, we have extended these results, using the recent EEL data of [3], to include the unfolding of better resolved features above ~13

Broadband transient absorption spectroscopy with 1- and 2-photon excitations: Relaxation paths and cross sections of a triphenylamine dye in solution

Energy Technology Data Exchange (ETDEWEB)

Moreno, J.; Dobryakov, A. L.; Hecht, S., E-mail: sh@chemie.hu-berlin.de, E-mail: skovale@chemie.hu-berlin.de; Kovalenko, S. A., E-mail: sh@chemie.hu-berlin.de, E-mail: skovale@chemie.hu-berlin.de [Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-St. 2, 12489 Berlin (Germany); Ioffe, I. N. [Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Granovsky, A. A. [Firefly Project, 117593 Moscow (Russian Federation)

2015-07-14

1-photon (382 nm) and 2-photon (752 nm) excitations to the S{sub 1} state are applied to record and compare transient absorption spectra of a push-pull triphenylamine (TrP) dye in solution. After 1-photon excitation, ultrafast vibrational and structural molecular relaxations are detected on a 0.1 ps time scale in nonpolar hexane, while in polar acetonitrile, the spectral evolution is dominated by dipolar solvation. Upon 2-photon excitation, transient spectra in hexane reveal an unexpected growth of stimulated emission (SE) and excited-state absorption (ESA) bands. The behavior is explained by strong population transfer S{sub 1} → S{sub n} due to resonant absorption of a third pump photon. Subsequent S{sub n} → S{sub 1} internal conversion (with τ{sub 1} = 1 ps) prepares a very hot S{sub 1} state which cools down with τ{sub 2} = 13 ps. The pump pulse energy dependence proves the 2-photon origin of the bleach signal. At the same time, SE and ESA are strongly affected by higher-order pump absorptions that should be taken into account in nonlinear fluorescence applications. The 2-photon excitation cross sections σ{sup (2)} = 32 ⋅ 10{sup −50} cm{sup 4} s at 752 nm are evaluated from the bleach signal.

Laboratory characterization and astrophysical detection of vibrationally excited states of vinyl cyanide in Orion-KL

Science.gov (United States)

López, A.; Tercero, B.; Kisiel, Z.; Daly, A. M.; Bermúdez, C.; Calcutt, H.; Marcelino, N.; Viti, S.; Drouin, B. J.; Medvedev, I. R.; Neese, C. F.; Pszczółkowski, L.; Alonso, J. L.; Cernicharo, J.

2014-12-01

Context. We perform a laboratory characterization in the 18-1893 GHz range and astronomical detection between 80-280 GHz in Orion-KL with IRAM-30 m of CH2CHCN (vinyl cyanide) in its ground and vibrationally excited states. Aims: Our aim is to improve the understanding of rotational spectra of vibrationally excited vinyl cyanide with new laboratory data and analysis. The laboratory results allow searching for these excited state transitions in the Orion-KL line survey. Furthermore, rotational lines of CH2CHCN contribute to the understanding of the physical and chemical properties of the cloud. Methods: Laboratory measurements of CH2CHCN made on several different frequency-modulated spectrometers were combined into a single broadband 50-1900 GHz spectrum and its assignment was confirmed by Stark modulation spectra recorded in the 18-40 GHz region and by ab-initio anharmonic force field calculations. For analyzing the emission lines of vinyl cyanide detected in Orion-KL we used the excitation and radiative transfer code (MADEX) at LTE conditions. Results: Detailed characterization of laboratory spectra of CH2CHCN in nine different excited vibrational states: ν11 = 1, ν15 = 1, ν11 = 2, ν10 = 1 ⇔ (ν11 = 1,ν15 = 1), ν11 = 3/ν15 = 2/ν14 = 1, (ν11 = 1,ν10 = 1) ⇔ (ν11 = 2,ν15 = 1), ν9 = 1, (ν11 = 1,ν15 = 2) ⇔ (ν10 = 1,ν15 = 1) ⇔ (ν11 = 1,ν14 = 1), and ν11 = 4 are determined, as well as the detection of transitions in the ν11 = 2 and ν11 = 3 states for the first time in Orion-KL and of those in the ν10 = 1 ⇔ (ν11 = 1,ν15 = 1) dyad of states for the first time in space. The rotational transitions of the ground state of this molecule emerge from four cloud components of hot core nature, which trace the physical and chemical conditions of high mass star forming regions in the Orion-KL Nebula. The lowest energy vibrationally excited states of vinyl cyanide, such as ν11 = 1 (at 328.5 K), ν15 = 1 (at 478.6 K), ν11 = 2 (at 657.8 K), the ν10

Excited state dynamics of DNA bases

Czech Academy of Sciences Publication Activity Database

Kleinermanns, K.; Nachtigallová, Dana; de Vries, M. S.

2013-01-01

Roč. 32, č. 2 (2013), s. 308-342 ISSN 0144-235X R&D Projects: GA ČR GAP208/12/1318 Grant - others:National Science Foundation(US) CHE-0911564; NASA (US) NNX12AG77G; Deutsche Forschungsgemeinschaft(DE) SFB 663; Deutsche Forschungsgemeinschaft(DE) KI 531-29 Institutional support: RVO:61388963 Keywords : DNA bases * nucleobases * excited state * dynamics * computations * gas phase * conical intersections Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.920, year: 2013

Triplet state photochemistry and the three-state crossing of acetophenone within time-dependent density-functional theory