Multipulse spectroscopy on the wild-type and YM210W Bacterial Reaction Centre uncovers a new intermediate state in the special pair excited state

Science.gov (United States)

Cohen Stuart, T. A.; van Grondelle, R.

2009-06-01

The Bacterial Reaction Centre (BRC) has a complex electronic excited state, P ∗, that evolves into subsequent charge separated product states P +H - and P +B -. Pump-dump-probe spectroscopy on the wild-type BRC and on YM210W, a mutant with a stabilized, long-lived P ∗ excited state, has uncovered a new charge-separated state in both BRC's. When P ∗ is dumped, a fraction of its population is transferred to this state that has a strong Stark shift in the accessory bacteriochlorophyll (B M) region which serves as a signature for P + and a lifetime highly comparable to the slow phase of P ∗ decay. This lead us propose this intermediate to be P +/P -.

Room temperature excitation spectroscopy of single quantum dots

Directory of Open Access Journals (Sweden)

Christian Blum

2011-08-01

Full Text Available We report a single molecule detection scheme to investigate excitation spectra of single emitters at room temperature. We demonstrate the potential of single emitter photoluminescence excitation spectroscopy by recording excitation spectra of single CdSe nanocrystals over a wide spectral range of 100 nm. The spectra exhibit emission intermittency, characteristic of single emitters. We observe large variations in the spectra close to the band edge, which represent the individual heterogeneity of the observed quantum dots. We also find specific excitation wavelengths for which the single quantum dots analyzed show an increased propensity for a transition to a long-lived dark state. We expect that the additional capability of recording excitation spectra at room temperature from single emitters will enable insights into the photophysics of emitters that so far have remained inaccessible.

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

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.

Measuring 13Cβ chemical shifts of invisible excited states in proteins by relaxation dispersion NMR spectroscopy

International Nuclear Information System (INIS)

Lundstroem, Patrik; Lin Hong; Kay, Lewis E.

2009-01-01

A labeling scheme is introduced that facilitates the measurement of accurate 13 C β chemical shifts of invisible, excited states of proteins by relaxation dispersion NMR spectroscopy. The approach makes use of protein over-expression in a strain of E. coli in which the TCA cycle enzyme succinate dehydrogenase is knocked out, leading to the production of samples with high levels of 13 C enrichment (30-40%) at C β side-chain carbon positions for 15 of the amino acids with little 13 C label at positions one bond removed (∼5%). A pair of samples are produced using [1- 13 C]-glucose/NaH 12 CO 3 or [2- 13 C]-glucose as carbon sources with isolated and enriched (>30%) 13 C β positions for 11 and 4 residues, respectively. The efficacy of the labeling procedure is established by NMR spectroscopy. The utility of such samples for measurement of 13 C β chemical shifts of invisible, excited states in exchange with visible, ground conformations is confirmed by relaxation dispersion studies of a protein-ligand binding exchange reaction in which the extracted chemical shift differences from dispersion profiles compare favorably with those obtained directly from measurements on ligand free and fully bound protein samples

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

Two-photon-excited fluorescence spectroscopy of atomic fluorine at 170 nm

Science.gov (United States)

Herring, G. C.; Dyer, Mark J.; Jusinski, Leonard E.; Bischel, William K.

1988-01-01

Two-photon-excited fluorescence spectroscopy of atomic fluorine is reported. A doubled dye laser at 286-nm is Raman shifted in H2 to 170 nm (sixth anti-Stokes order) to excite ground-state 2P(0)J fluorine atoms to the 2D(0)J level. The fluorine atoms are detected by one of two methods: observing the fluorescence decay to the 2PJ level or observing F(+) production through the absorption of an additional photon by the excited atoms. Relative two-photon absorption cross sections to and the radiative lifetimes of the 2D(0)J states are measured.

Low-energy d-d excitations in MnO studied by resonant x-ray fluorescence spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Butorin, S.M.; Guo, J.; Magnuson, M. [Uppsala Univ. (Sweden)] [and others

1997-04-01

Resonant soft X-ray emission spectroscopy has been demonstrated to possess interesting abilities for studies of electronic structure in various systems, such as symmetry probing, alignment and polarization dependence, sensitivity to channel interference, etc. In the present abstract the authors focus on the feasibility of resonant soft X-ray emission to probe low energy excitations by means of resonant electronic X-ray Raman scattering. Resonant X-ray emission can be regarded as an inelastic scattering process where a system in the ground state is transferred to a low excited state via a virtual core excitation. The energy closeness to a core excitation of the exciting radiation enhances the (generally) low probability for inelastic scattering at these wavelengths. Therefore soft X-ray emission spectroscopy (in resonant electronic Raman mode) can be used to study low energy d-d excitations in transition metal systems. The involvement of the intermediate core state allows one to use the selection rules of X-ray emission, and the appearance of the elastically scattered line in the spectra provides the reference to the ground state.

Low-energy d-d excitations in MnO studied by resonant x-ray fluorescence spectroscopy

International Nuclear Information System (INIS)

Butorin, S.M.; Guo, J.; Magnuson, M.

1997-01-01

Resonant soft X-ray emission spectroscopy has been demonstrated to possess interesting abilities for studies of electronic structure in various systems, such as symmetry probing, alignment and polarization dependence, sensitivity to channel interference, etc. In the present abstract the authors focus on the feasibility of resonant soft X-ray emission to probe low energy excitations by means of resonant electronic X-ray Raman scattering. Resonant X-ray emission can be regarded as an inelastic scattering process where a system in the ground state is transferred to a low excited state via a virtual core excitation. The energy closeness to a core excitation of the exciting radiation enhances the (generally) low probability for inelastic scattering at these wavelengths. Therefore soft X-ray emission spectroscopy (in resonant electronic Raman mode) can be used to study low energy d-d excitations in transition metal systems. The involvement of the intermediate core state allows one to use the selection rules of X-ray emission, and the appearance of the elastically scattered line in the spectra provides the reference to the ground state

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

Core excitation and de-excitation spectroscopies of free atoms and molecules

International Nuclear Information System (INIS)

Ueda, Kiyoshi

2006-01-01

This article provides a review of the current status of core excitation and de-excitation spectroscopy studies of free atoms molecules using a high-resolution soft X-ray monochromator and a high-resolution electron energy analyzer, installed in the soft X-ray photochemistry beam line at SPring-8. Experimental results are discussed for 1s excitation of Ne, O 1s excitation of CO and H 2 O, and F 1s excitation of CF 4 . (author)

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

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

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.

Femtosecond stimulated Raman spectroscopy as a tool to detect molecular vibrations in ground and excited electronic states

Energy Technology Data Exchange (ETDEWEB)

Gelin, Maxim F.; Domcke, Wolfgang [Department of Chemistry, Technische Universität München, D-85747 Garching (Germany); Rao, B. Jayachander [Departamento de Química and Centro de Química, Universidade de Coimbra, 3004-535 Coimbra (Portugal)

2016-05-14

We give a detailed theoretical analysis of the simplest variant of femtosecond stimulated Raman spectroscopy, where a picosecond Raman pump pulse and a femtosecond Raman probe pulse are applied resonantly to a chromophore in thermal equilibrium in the ground electronic state. We demonstrate that this technique is capable of the detection of dephasing-free Raman-like lines revealing vibrational modes not only in the electronic ground state but also in the excited electronic state of the chromophore. The analytical results obtained with simplifying assumptions for the shape of the laser pulses are substantiated by numerical simulations with realistic laser pulses, employing the equation-of-motion phase-matching approach.

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.

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

Laser techniques for spectroscopy of core-excited atomic levels

Science.gov (United States)

Harris, S. E.; Young, J. F.; Falcone, R. W.; Rothenberg, J. E.; Willison, J. R.

1982-01-01

We discuss three techniques which allow the use of tunable lasers for high resolution and picosecond time scale spectroscopy of core-excited atomic levels. These are: anti-Stokes absorption spectroscopy, laser induced emission from metastable levels, and laser designation of selected core-excited levels.

On the investigation of electronic defect states in ZnO thin films by space charge spectroscopy with optical excitation

Science.gov (United States)

Schmidt, Matthias; Wenckstern, Holger von; Pickenhain, Rainer; Grundmann, Marius

2012-09-01

Electronic defect states in a n-type conducting zinc oxide thin film sample were investigated by means of space charge spectroscopy focussing on levels in the midgap region as well as on hole traps. To overcome the experimental difficulties arising from the wide bandgap and the lack of p-type conduction, optical excitation was employed to measure the emission of trapped charge carriers from these levels. Therefore - besides deep-level transient spectroscopy measurements - photo-capacitance, optically chopped photo-current, minority carrier transient spectroscopy, and optical capacitance-voltage experiments were conducted. In doing so, a midgap level labelled T4, and hole traps labelled TH1 and TH2 were detected. In the case of T4 and TH1 the photo-ionisation cross-section spectra were determined.

Hertzian spectroscopy application to excited states in accelerated ion beams

Energy Technology Data Exchange (ETDEWEB)

Gaillard, M L

1974-01-01

Accelerated ion beams enables the application of optical hertzian spectrometry methods to be extended to research on the excited states of free ionic systems. The photon beat method has proved especially simple to apply in beam foil geometry because of the unidirectional beam velocity while the beam gas device is suitable for experiments of the energy level crossing type. Only the resonance technique involving direct application of high-frequency magnetic fields poses serious problems because of the high HF powers necessary. So far structure intervals have been measured in ions carrying up to three charges (seven in the special case of Lamb shift measurements) with a precision of a few percent. Study of hydrogen-like or helium-like ions of high Z allows the fundamental calculations of quantum electrodynamics to be checked with regard to the Lamb shift or the spontaneous emission theory. In more complex electronic systems, optical spectroscopy of accelerated ion beams gives wavelengths with a resolution reaching 10/sup -5/, lifetimes with an accuracy better than 10% when the cascade effects are properly studied, and Lande factors with a precision of several % under present technical conditions. The photon beat method concerns hyperfine nuclear effects in light atoms of Z < = 20. (FR)

Single-photon cesium Rydberg excitation spectroscopy using 318.6-nm UV laser and room-temperature vapor cell.

Science.gov (United States)

Wang, Jieying; Bai, Jiandong; He, Jun; Wang, Junmin

2017-09-18

We demonstrate a single-photon Rydberg excitation spectroscopy of cesium (Cs) atoms in a room-temperature vapor cell. Cs atoms are excited directly from 6S 1/2 ground state to nP 3/2 (n = 70 - 100) Rydberg states with a 318.6 nm ultraviolet (UV) laser, and Rydberg excitation spectra are obtained by transmission enhancement of a probe beam resonant to Cs 6S 1/2 , F = 4 - 6P 3/2 , F' = 5 transition as partial population on F = 4 ground state are transferred to Rydberg state. Analysis reveals that the observed spectra are velocity-selective spectroscopy of Rydberg state, from which the amplitude and linewidth influenced by lasers' Rabi frequency have been investigated. Fitting to energies of Cs nP 3/2 (n = 70 -100) states, the determined quantum defect is 3.56671(42). The demodulated spectra can also be employed as frequency references to stabilize the UV laser frequency to specific Cs Rydberg transition.

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

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.

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.

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

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

Electronic excitation of furfural as probed by high-resolution vacuum ultraviolet spectroscopy, electron energy loss spectroscopy, and ab initio calculations

Science.gov (United States)

Ferreira da Silva, F.; Lange, E.; Limão-Vieira, P.; Jones, N. C.; Hoffmann, S. V.; Hubin-Franskin, M.-J.; Delwiche, J.; Brunger, M. J.; Neves, R. F. C.; Lopes, M. C. A.; de Oliveira, E. M.; da Costa, R. F.; Varella, M. T. do N.; Bettega, M. H. F.; Blanco, F.; García, G.; Lima, M. A. P.; Jones, D. B.

2015-10-01

The electronic spectroscopy of isolated furfural (2-furaldehyde) in the gas phase has been investigated using high-resolution photoabsorption spectroscopy in the 3.5-10.8 eV energy-range, with absolute cross section measurements derived. Electron energy loss spectra are also measured over a range of kinematical conditions. Those energy loss spectra are used to derive differential cross sections and in turn generalised oscillator strengths. These experiments are supported by ab initio calculations in order to assign the excited states of the neutral molecule. The good agreement between the theoretical results and the measurements allows us to provide the first quantitative assignment of the electronic state spectroscopy of furfural over an extended energy range.

Electronic excitation of furfural as probed by high-resolution vacuum ultraviolet spectroscopy, electron energy loss spectroscopy, and ab initio calculations

International Nuclear Information System (INIS)

Ferreira da Silva, F.; Lange, E.; Limão-Vieira, P.; Jones, N. C.; Hoffmann, S. V.; Hubin-Franskin, M.-J.; Delwiche, J.; Brunger, M. J.

2015-01-01

The electronic spectroscopy of isolated furfural (2-furaldehyde) in the gas phase has been investigated using high-resolution photoabsorption spectroscopy in the 3.5–10.8 eV energy-range, with absolute cross section measurements derived. Electron energy loss spectra are also measured over a range of kinematical conditions. Those energy loss spectra are used to derive differential cross sections and in turn generalised oscillator strengths. These experiments are supported by ab initio calculations in order to assign the excited states of the neutral molecule. The good agreement between the theoretical results and the measurements allows us to provide the first quantitative assignment of the electronic state spectroscopy of furfural over an extended energy range

Electronic excitation of furfural as probed by high-resolution vacuum ultraviolet spectroscopy, electron energy loss spectroscopy, and ab initio calculations

Energy Technology Data Exchange (ETDEWEB)

Ferreira da Silva, F.; Lange, E. [Laboratório de Colisões Atómicas e Moleculares, CEFITEC, Departamento de Física, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Limão-Vieira, P., E-mail: plimaovieira@fct.unl.pt, E-mail: michael.brunger@flinders.edu.au, E-mail: maplima@ifi.unicamp.br [Laboratório de Colisões Atómicas e Moleculares, CEFITEC, Departamento de Física, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001 (Australia); Jones, N. C.; Hoffmann, S. V. [ISA, Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Århus C (Denmark); Hubin-Franskin, M.-J.; Delwiche, J. [Départment de Chimie, Institut de Chimie-Bât. B6C, Université de Liège, B-4000 Liège 1 (Belgium); Brunger, M. J., E-mail: plimaovieira@fct.unl.pt, E-mail: michael.brunger@flinders.edu.au, E-mail: maplima@ifi.unicamp.br [School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, South Australia 5001 (Australia); Institute of Mathematical Sciences, University of Malaya, 50603 Kuala Lumpur (Malaysia); and others

2015-10-14

The electronic spectroscopy of isolated furfural (2-furaldehyde) in the gas phase has been investigated using high-resolution photoabsorption spectroscopy in the 3.5–10.8 eV energy-range, with absolute cross section measurements derived. Electron energy loss spectra are also measured over a range of kinematical conditions. Those energy loss spectra are used to derive differential cross sections and in turn generalised oscillator strengths. These experiments are supported by ab initio calculations in order to assign the excited states of the neutral molecule. The good agreement between the theoretical results and the measurements allows us to provide the first quantitative assignment of the electronic state spectroscopy of furfural over an extended energy range.

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.

Excitation transfer and trapping kinetics in plant photosystem I probed by two-dimensional electronic spectroscopy.

Science.gov (United States)

Akhtar, Parveen; Zhang, Cheng; Liu, Zhengtang; Tan, Howe-Siang; Lambrev, Petar H

2018-03-01

Photosystem I is a robust and highly efficient biological solar engine. Its capacity to utilize virtually every absorbed photon's energy in a photochemical reaction generates great interest in the kinetics and mechanisms of excitation energy transfer and charge separation. In this work, we have employed room-temperature coherent two-dimensional electronic spectroscopy and time-resolved fluorescence spectroscopy to follow exciton equilibration and excitation trapping in intact Photosystem I complexes as well as core complexes isolated from Pisum sativum. We performed two-dimensional electronic spectroscopy measurements with low excitation pulse energies to record excited-state kinetics free from singlet-singlet annihilation. Global lifetime analysis resolved energy transfer and trapping lifetimes closely matches the time-correlated single-photon counting data. Exciton energy equilibration in the core antenna occurred on a timescale of 0.5 ps. We further observed spectral equilibration component in the core complex with a 3-4 ps lifetime between the bulk Chl states and a state absorbing at 700 nm. Trapping in the core complex occurred with a 20 ps lifetime, which in the supercomplex split into two lifetimes, 16 ps and 67-75 ps. The experimental data could be modelled with two alternative models resulting in equally good fits-a transfer-to-trap-limited model and a trap-limited model. However, the former model is only possible if the 3-4 ps component is ascribed to equilibration with a "red" core antenna pool absorbing at 700 nm. Conversely, if these low-energy states are identified with the P 700 reaction centre, the transfer-to-trap-model is ruled out in favour of a trap-limited model.

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.

Emission and absorption spectroscopy study of Ar excited states in 13.56 MHz argon plasma operating at sub-atmospheric to atmospheric pressure

Energy Technology Data Exchange (ETDEWEB)

Li, L. [Department of Applied Physics, Research Unit Plasma Technology, Ghent University, Jozef Plateaustraat 22, Ghent B-9000 (Belgium); Nikiforov, A., E-mail: anton.nikiforov@ugent.be [Department of Applied Physics, Research Unit Plasma Technology, Ghent University, Jozef Plateaustraat 22, Ghent B-9000 (Belgium); Institute of Solution Chemistry of the Russian Academy of Science, Academicheskaya St., 1, Ivanovo, 153045 (Russian Federation); Britun, N. [Chimie des Interactions Plasma-Surface (ChIPS), CIRMAP, Universite de Mons, 23 Place du Parc, B-7000 Mons (Belgium); Snyders, R. [Chimie des Interactions Plasma-Surface (ChIPS), CIRMAP, Universite de Mons, 23 Place du Parc, B-7000 Mons (Belgium); Materia Nova Research Centre, Parc Initialis, B-7000 Mons (Belgium); Leys, C. [Department of Applied Physics, Research Unit Plasma Technology, Ghent University, Jozef Plateaustraat 22, Ghent B-9000 (Belgium)

2015-05-01

The densities of metastable and resonant states of Ar atoms are measured in high pressure Ar radio frequency discharge. Resonant absorption spectroscopy for the case of a low pressure spectral lamp and high-pressure plasma absorption lines is implemented for this purpose. The necessary generalizations for the high-pressure resonant absorption method are given. Absolute density of Ar 1s levels obtained at different RF input power and operating pressures are of the order of 10{sup 11} cm{sup −3}, which is in a good agreement with those reported in the literature. The population distribution on the Ar 2p (excited) levels, obtained from the optical emission spectroscopy, reveals strong deviation from thermal equilibrium for these levels in the high-pressure case. The generation of the Ar excited states in the studied discharges is compared to the previously reported results. - Highlights: • Strong non-equilibrium distribution of Ar 2p levels is observed. • The absolute number density of non-radiative Ar 1s states is determined by the easier and low cost spectral-lamp absorption method. • The modified absorption theory of Mitchell and Zemanski was used to obtain the absolute number density of Ar 1s states at high pressure. • The developed RF source with 5 cm long gap can be a possible alternative to micro-plasma working in Ar at atmospheric pressure.

Spectroscopy at the two-proton drip line: Excited states in 158W

Directory of Open Access Journals (Sweden)

D.T. Joss

2017-09-01

Full Text Available Excited states have been identified in the heaviest known even-Z N=84 isotone 158W, which lies in a region of one-proton emitters and the two-proton drip line. The observation of γ-ray transitions feeding the ground state establishes the excitation energy of the yrast 6+ state confirming the spin-gap nature of the α-decaying 8+ isomer. The 8+ isomer is also expected to be unbound to two-proton emission but no evidence for this decay mode was observed. An upper limit for the two-proton decay branch has been deduced as b2p≤ 0.17% at the 90% confidence level. The possibility of observing two-proton emission from multiparticle isomers in nearby nuclides is considered.

Spectroscopy at the two-proton drip line: Excited states in 158W

Science.gov (United States)

Joss, D. T.; Page, R. D.; Herzán, A.; Donosa, L.; Uusitalo, J.; Carroll, R. J.; Darby, I. G.; Andgren, K.; Cederwall, B.; Eeckhaudt, S.; Grahn, T.; Greenlees, P. T.; Hadinia, B.; Jakobsson, U.; Jones, P. M.; Julin, R.; Juutinen, S.; Leino, M.; Leppanen, A.-P.; Nyman, M.; O'Donnell, D.; Pakarinen, J.; Rahkila, P.; Sandzelius, M.; Sarén, J.; Scholey, C.; Seweryniak, D.; Simpson, J.; Sorri, J.

2017-09-01

Excited states have been identified in the heaviest known even-Z N = 84 isotone 158W, which lies in a region of one-proton emitters and the two-proton drip line. The observation of γ-ray transitions feeding the ground state establishes the excitation energy of the yrast 6+ state confirming the spin-gap nature of the α-decaying 8+ isomer. The 8+ isomer is also expected to be unbound to two-proton emission but no evidence for this decay mode was observed. An upper limit for the two-proton decay branch has been deduced as b2p ≤ 0.17% at the 90% confidence level. The possibility of observing two-proton emission from multiparticle isomers in nearby nuclides is considered.

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

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

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.

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.

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.

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.

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.

Studies of photoionization processes from ground-state and excited-state atoms and molecules

International Nuclear Information System (INIS)

Ederer, D.L.; Parr, A.C.; West, J.B.

1982-01-01

Recent triply-differential photoelectron spectroscopy experiments designed for the study of correlation effects in atoms and molecules are described. Final-state symmetry of the n=2 state of helium has been determined. The non-Franck-Condon behavior of vibrational branching ratios and large variations of the angular asymmetry parameter has been observed for shape resonances and autoionizing resonances in CO and other molecules. Recent observations of the photoionization of excited sodium atoms are also described

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

Liquid-Arc/Spark-Excitation Atomic-Emission Spectroscopy

Science.gov (United States)

Schlagen, Kenneth J.

1992-01-01

Constituents of solutions identified in situ. Liquid-arc/spark-excitation atomic-emission spectroscopy (LAES) is experimental variant of atomic-emission spectroscopy in which electric arc or spark established in liquid and spectrum of light from arc or spark analyzed to identify chemical elements in liquid. Observations encourage development of LAES equipment for online monitoring of process streams in such industries as metal plating, electronics, and steel, and for online monitoring of streams affecting environment.

High-Resolution Spectroscopy of Jet-Cooled 1,1 '-Diphenylethylene: Electronically Excited and Ionic States of a Prototypical Cross-Conjugated System

NARCIS (Netherlands)

Smolarek, S.; Vdovin, A.; Rijs, A.; van Walree, C. A.; Zgierski, M. Z.; Buma, W. J.

2011-01-01

The photophysics of a prototypical cross-conjugated pi-system, 1,1'-diphenylethylene, have been studied using high-resolution resonance enhanced multiphoton ionization excitation spectroscopy and zero kinetic energy photoelectron spectroscopy, in combination with advanced ab initio

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.)

Solvent control of charge transfer excited state relaxation pathways in [Fe(2,2 '-bipyridine)(CN)4]2-

DEFF Research Database (Denmark)

Kjær, Kasper Skov; Kunnus, Kristjan; Harlang, Tobias C. B.

2018-01-01

The excited state dynamics of solvated [Fe(bpy)(CN)4]2-, where bpy = 2,2'-bipyridine, show significant sensitivity to the solvent Lewis acidity. Using a combination of optical absorption and X-ray emission transient spectroscopies, we have previously shown that the metal to ligand charge transfer...... the MLCT excited state relaxation dynamics of [Fe(bpy)(CN)4]2- in water, a strong Lewis acid solvent. The charge-transfer excited state is now found to decay in less than 100 femtoseconds, forming a quasi-stable metal centered excited state with a 13 picosecond lifetime. We find that this MC excited state...... developed for solar applications....

Excited-state spectroscopy of singly, doubly and triply-charmed baryons from lattice QCD

Energy Technology Data Exchange (ETDEWEB)

Padmanath, M. [Tata Institute; Edwards, Robert G. [JLAB; Mathur, Nilmani [Tata Institute; Peardon, Michael [Trinity College

2014-07-01

We present the ground and excited state spectra of singly, doubly and triply-charmed baryons by using dynamical lattice QCD. A large set of baryonic operators that respect the symmetries of the lattice and are obtained after subduction from their continuum analogues are utilized. These operators transform as irreducible representations of SU(3)F symmetry for flavour, SU(4) symmetry for Dirac spins of quarks and O(3) symmetry for orbital angular momenta. Using novel computational techniques correlation functions of these operators are generated and the variational method is exploited to extract excited states. The lattice spectra that we obtain have baryonic states with well-defined total spins up to 7/2 and the low lying states remarkably resemble the expectations of quantum numbers from SU(6)ⓍO(3) symmetry.

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

Deciphering excited state evolution in halorhodopsin with stimulated emission pumping.

Science.gov (United States)

Bismuth, Oshrat; Komm, Pavel; Friedman, Noga; Eliash, Tamar; Sheves, Mordechai; Ruhman, Sanford

2010-03-04

The primary photochemical dynamics of Hb. pharaonis Halorhodopsin (pHR) are investigated by femtosecond visible pump-near IR dump-hyperspectral probe spectroscopy. The efficiency of excited state depletion is deduced from transient changes in absorption, recorded with and without stimulated emission pumping (SEP), as a function of the dump delay. The concomitant reduction of photocycle population is assessed by probing the "K" intermediate difference spectrum. Results show that the cross section for stimulating emission is nearly constant throughout the fluorescent state lifetime. Probing "K" demonstrates that dumping produces a proportionate reduction in photocycle yields. We conclude that, despite its nonexponential internal conversion (IC) kinetics, the fluorescent state in pHR constitutes a single intermediate in the photocycle. This contrasts with conclusions drawn from the study of primary events in the related chloride pump from Hb. salinarum (sHR), believed to produce the "K" intermediate from a distinct short-lived subpopulation in the excited state. Our discoveries concerning internal conversion dynamics in pHR are discussed in light of recent expectations for similar excited state dynamics in both proteins.

High-resolution spectroscopy of jet-cooled 1,1 '-diphenylethylene: electronically excited and ionic states of a prototypical cross-conjugated system

NARCIS (Netherlands)

Smolarek, S.; Vdovin, A.; Rijs, A.; van Walree, C.A.; Zgierski, M.Z.; Buma, W.J.

2011-01-01

The photophysics of a prototypical cross-conjugated π-system, 1,1′-diphenylethylene, have been studied using high-resolution resonance enhanced multiphoton ionization excitation spectroscopy and zero kinetic energy photoelectron spectroscopy, in combination with advanced ab initio calculations. We

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...

International conference: Features of nuclear excitation states and mechanisms of nuclear reactions. 51. Meeting on nuclear spectroscopy and nuclear structure. The book of abstracts

International Nuclear Information System (INIS)

2001-01-01

Results of the LI Meeting on Nuclear Spectroscopy and Nuclear Structure are presented. Properties of excited states of atomic nuclei and mechanisms of nuclear reactions are considered. Studies on the theory of nucleus and fundamental interactions pertinent to experimental study of nuclei properties and mechanisms of nuclear reactions, technique and methods of experiment, application of nuclear-physical method, are provided [ru

Effect of carotenoid structure on excited-state dynamics of carbonyl carotenoids

Czech Academy of Sciences Publication Activity Database

Chábera, P.; Fuciman, M.; Hříbek, P.; Polívka, Tomáš

2009-01-01

Roč. 11, - (2009), s. 8795-8703 ISSN 1463-9076 R&D Projects: GA AV ČR IAA608170604 Institutional research plan: CEZ:AV0Z50510513 Keywords : excited-state dynamics * carbonyl carotenoids * femtosecond spectroscopy Subject RIV: BO - Biophysics Impact factor: 4.116, year: 2009

Resonantly enhanced production of excited fragments of gaseous molecules following core-level excitation

International Nuclear Information System (INIS)

Chen, J.M.; Lu, K.T.; Lee, J.M.; Ho, S.C.; Chang, H.W.; Lee, Y.Y.

2005-01-01

State-selective dissociation dynamics for the excited fragments of gaseous Si(CH 3 ) 2 Cl 2 following Cl 2p and Si 2p core-level excitations have been investigated by resonant photoemission spectroscopy and dispersed UV/optical fluorescence spectroscopy. The main features in the gaseous Si(CH 3 ) 2 Cl 2 fluorescence spectrum are identified as the emission from excited Si*, Si + *, CH* and H*. The core-to-Rydberg excitations at both Si 2p and Cl 2p edges lead to a noteworthy production of not only the excited atomic fragments, neutral and ionic (Si*, Si + *) but also the excited diatomic fragments (CH*). In particular, the excited neutral atomic fragments Si* are significantly reinforced. The experimental results provide deeper insight into the state-selective dissociation dynamics for the excited fragments of molecules via core-level excitation

Laser-excited photoemission spectroscopy study of superconducting boron-doped diamond

Directory of Open Access Journals (Sweden)

K. Ishizaka, R. Eguchi, S. Tsuda, T. Kiss, T. Shimojima, T. Yokoya, S. Shin, T. Togashi, S. Watanabe, C.-T. Chen, C.Q. Zhang, Y. Takano, M. Nagao, I. Sakaguchi, T. Takenouchi and H. Kawarada

2006-01-01

Full Text Available We have investigated the low-energy electronic state of boron-doped diamond thin film by the laser-excited photoemission spectroscopy. A clear Fermi-edge is observed for samples doped above the semiconductor–metal boundary, together with the characteristic structures at 150×n meV possibly due to the strong electron–lattice coupling effect. In addition, for the superconducting sample, we observed a shift of the leading edge below Tc indicative of a superconducting gap opening. We discuss the electron–lattice coupling and the superconductivity in doped diamond.

Spectroscopy and intramolecular relaxation of methyl salicylate in its first excited singlet state

Science.gov (United States)

Kuper, Jerry W.; Perry, David S.

1984-05-01

High resolution fluorescence excitation experiments are reported for the blue emitting rotamer of methyl salicylate in its first excited singlet state. These experiments employ moderate expansions of methyl salicylate seeded in argon ( P0D=5-8 Torr cm) to achieve rotational and vibrational cooling in a pulsed supersonic jet. The rotational contour of the electronic origin at 30 055.3 cm-1 is shown to be consistent with a geometrically distorted π-π* excited state, partially polarized along the A axis and with a rotational temperature of 5-7 K. A noticeable broadening of the spectral features beyond the rotational contour begins at 500 cm-1 above the origin and then increases rapidly above 900 cm-1 reaching a width of 12 cm-1 near 1200 cm-1. The constancy of fluorescence decay lifetimes in this region indicate that intramolecular vibrational relaxation in the S1 manifold is the broadening mechanism.

Investigation of triply excited states of Li-like ions in fast ion-atom collisions by zero-degree Auger projectile electron spectroscopy

International Nuclear Information System (INIS)

Zouros, T.J.M.; Benis, E.P.; Zamkov, M.; Lin, C.D.; Lee, T.G.; Richard, P.; Gorczyca, T.W.; Morishita, T.

2005-01-01

The production of triply excited states of Li-like systems has recently been extended beyond the lithium atom using two different ion-atom collisional techniques: (a) Triple-electron capture into 2s2p 2 and 2p 3 states of F 6+ formed in fast collisions of bare F 9+ ions with Ar and Kr atoms and (b) 180 deg. resonant scattering of quasi-free electrons of H 2 from the 1s2s 3 S metastable state of He-like B, C, N, O and F ions via the 2s2p 2 2 D resonance. Autoionization energies, decay branching ratios and production cross sections for these states were measured using zero-degree Auger projectile electron spectroscopy and compared to theoretical calculations using hyperspherical close coupling (HSCC) and R-matrix methods

Two-photon excitation spectroscopy of carotenoid-containing and carotenoid-depleted LH2 complexes from purple bacteria.

Science.gov (United States)

Stepanenko, Ilya; Kompanetz, Viktor; Makhneva, Zoya; Chekalin, Sergey; Moskalenko, Andrei; Razjivin, Andrei

2009-08-27

We applied two-photon fluorescence excitation spectroscopy to LH2 complex from purple bacteria Allochromatium minutissimum and Rhodobacter sphaeroides . Bacteriochlorophyll fluorescence was measured under two-photon excitation of the samples within the 1200-1500 nm region. Spectra were obtained for both carotenoid-containing and -depleted complexes of each bacterium to allow their direct comparison. The depletion of carotenoids did not alter the two-photon excitation spectra of either bacteria. The spectra featured a wide excitation band around 1350 nm (2x675 nm, 14,800 cm(-1)) which strongly resembled two-photon fluorescence excitation spectra of similar complexes published by other authors. We consider obtained experimental data to be evidence of direct two-photon excitation of bacteriochlorophyll excitonic states in this spectral region.

Excited state dynamics & optical control of molecular motors

Science.gov (United States)

Wiley, Ted; Sension, Roseanne

2014-03-01

Chiral overcrowded alkenes are likely candidates for light driven rotary molecular motors. At their core, these molecular motors are based on the chromophore stilbene, undergoing ultrafast cis/trans photoisomerization about their central double bond. Unlike stilbene, the photochemistry of molecular motors proceeds in one direction only. This unidirectional rotation is a result of helicity in the molecule induced by steric hindrance. However, the steric hindrance which ensures unidirectional excited state rotation, has the unfortunate consequence of producing large ground state barriers which dramatically decrease the overall rate of rotation. These molecular scale ultrafast motors have only recently been studied by ultrafast spectroscopy. Our lab has studied the photochemistry and photophysics of a ``first generation'' molecular motor with UV-visible transient absorption spectroscopy. We hope to use optical pulse shaping to enhance the efficiency and turnover rate of these molecular motors.

Room temperature triplet state spectroscopy of organic semiconductors.

Science.gov (United States)

Reineke, Sebastian; Baldo, Marc A

2014-01-21

Organic light-emitting devices and solar cells are devices that create, manipulate, and convert excited states in organic semiconductors. It is crucial to characterize these excited states, or excitons, to optimize device performance in applications like displays and solar energy harvesting. This is complicated if the excited state is a triplet because the electronic transition is 'dark' with a vanishing oscillator strength. As a consequence, triplet state spectroscopy must usually be performed at cryogenic temperatures to reduce competition from non-radiative rates. Here, we control non-radiative rates by engineering a solid-state host matrix containing the target molecule, allowing the observation of phosphorescence at room temperature and alleviating constraints of cryogenic experiments. We test these techniques on a wide range of materials with functionalities spanning multi-exciton generation (singlet exciton fission), organic light emitting device host materials, and thermally activated delayed fluorescence type emitters. Control of non-radiative modes in the matrix surrounding a target molecule may also have broader applications in light-emitting and photovoltaic devices.

Isoelectronic study of triply excited Li-like states

International Nuclear Information System (INIS)

Benis, E P; Zouros, T J M; Gorczyca, T W; Zamkov, M; Richard, P

2003-01-01

Absolute doubly differential cross sections (DDCSs) for the production and Auger decay of the intra-shell 2s2p 22 D triply excited state formed in collisions of He-like ions (Z = 5-9) with H 2 were determined experimentally, using zero-degree Auger projectile electron spectroscopy. The 2 D e state was directly produced by 180 deg. resonant scattering of the quasi-free H 2 electrons from the 1s2s 3 S metastable state of the ion. Resonant energies and DDCSs calculated using the R-matrix approach within the electron scattering model were found to be in good overall agreement with experiment. (letter to the editor)

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.

Spectroscopy of weakly-bound complexes in highly excited electronic states: the He-I2(E3Πg) ion-pair state

International Nuclear Information System (INIS)

Prosmiti, Rita; Valdés, Álvaro; Kalemost, Apostolos

2014-01-01

The study of electronically excited van der Waals (vdW) systems presents a challenge for the theory of intermolecular interactions, and here we show how far ab initio computations can go. We found that the interaction energies for such electronically excited systems can indeed be determined, providing a reliable and accurate description for the E state potential of the HeI 2 , that in combination with the ground X and electronic excited B state of the complex, is useful to model experimental data related with potential minima and also predict higher vibrational vdW states

Broadband Doppler-limited two-photon and stepwise excitation spectroscopy with laser frequency combs

Science.gov (United States)

Hipke, Arthur; Meek, Samuel A.; Ideguchi, Takuro; Hänsch, Theodor W.; Picqué, Nathalie

2014-07-01

Multiplex two-photon excitation spectroscopy is demonstrated at Doppler-limited resolution. We describe first Fourier-transform two-photon spectroscopy of an atomic sample with two mode-locked laser oscillators in a dual-comb technique. Each transition is uniquely identified by the modulation imparted by the interfering comb excitations. The temporal modulation of the spontaneous two-photon fluorescence is monitored with a single photodetector, and the spectrum of all excited transitions is revealed by a Fourier transform.

Microwave spectroscopy of HCOO13CH3 in the second methyl torsional excited state

Science.gov (United States)

Kobayashi, Kaori; Kuwahara, Takuro; Tachi, Haruka; Urata, Yuki; Tsunekawa, Shozo; Hayashi, Naoto; Higuchi, Hiroyuki; Fujitake, Masaharu; Ohashi, Nobukimi

2018-01-01

The new experimental results and analysis of the microwave spectra of HCOO13CH3 in the second methyl torsional excited state are reported. Pseudo-principal axis method (pseudo-PAM) was successfully applied to the normal methyl formate in the second torsional excited state and again applied to this isotopologue. We succeeded to assign 536 A-species transitions up to J = 33 and Ka = 15 and 417 E-species transitions up to J = 32 and Ka = 14. Thirty parameters were used to do the least-squares-analysis by using the pseudo-PAM Hamiltonian consisting of rotational, centrifugal distortion, and internal-rotational constants.

Millimeterwave spectroscopy of active laser plasmas; the excited vibrational states of HCN

International Nuclear Information System (INIS)

De Lucia, F.C.; Helminger, P.A.

1977-01-01

Millimeter and submillimeter microwave techniques have been used for the spectroscopic study of an HCN laser plasma. Forty-seven rotational transitions in 12 excited vibrational states have been observed. Numerous rotational, vibrational, and perturbation parameters have been calculated from these data. A discussion of experimental techniques is included

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 .

Influence of the excited states on the electron-energy distribution function in low-pressure microwave argon plasmas

International Nuclear Information System (INIS)

Yanguas-Gil, A.; Cotrino, J.; Gonzalez-Elipe, A.R.

2005-01-01

In this work the influence of the excited states on the electron-energy distribution function has been determined for an argon microwave discharge at low pressure. A collisional-radiative model of argon has been developed taking into account the most recent experimental and theoretical values of argon-electron-impact excitation cross sections. The model has been solved along with the electron Boltzmann equation in order to study the influence of the inelastic collisions from the argon excited states on the electron-energy distribution function. Results show that under certain conditions the excited states can play an important role in determining the shape of the distribution function and the mean kinetic energy of the electrons, deplecting the high-energy tail due to inelastic processes from the excited states, especially from the 4s excited configuration. It has been found that from the populations of the excited states an excitation temperature can be defined. This excitation temperature, which can be experimentally determined by optical emission spectroscopy, is lower than the electron kinetic temperature obtained from the electron-energy distribution function

The Microwave Spectroscopy of HCOO^{13}CH_3 in the Second Torsional Excited State

Science.gov (United States)

Kobayashi, Kaori; Kuwahara, Takuro; Urata, Yuki; Ohashi, Nobukimi; Fujitake, Masaharu

2017-06-01

Methyl formate (HCOOCH_3) is an abundant interstellar molecule, found almost everywhere in the star-forming region. The interstellar abundance of the ^{13}C is about 1/50 of ^{12}C. The ^{13}C substituted methyl formate in the ground and first excited states were already found toward massive star-forming regions including Orion KL. With the aid of the state-of-the-art telescope like ALMA, the pure rotational transitions in the second torsional excited may be identified in the near future and laboratory data are necessary. We recorded the spectra of HCOOCH_3 below 340 GHz by using conventional source-modulation microwave spectrometer. The assignment of the pure rotational spectra in the second torsional excited state and the analysis by using pseudo-PAM Hamiltonian, which was effective to analyze the normal species, will be reported. C. Favre, M. Carvajal, D. Field, J. K. Jørgensen, S. E. Bisschop, N. Brouillet, D. Despois, A. Baudry, I. Kleiner, E. A. Bergin, N. R. Crockett, J. L. Neill, L. Marguès, T. R. Huet, and J. Demaison, Astrophys. J. Suppl. Ser. 215, 25 (2014).

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.

Excited states above the proton threshold in {sup 26}Si

Energy Technology Data Exchange (ETDEWEB)

Komatsubara, T. [Institute for Basic Science (IBS), Rare Isotope Science Project, Yuseong-gu Daejeon (Korea, Republic of); Kubono, S.; Ito, Y. [RIKEN, Saitama (Japan); Hayakawa, T.; Shizuma, T. [Japan Atomic Energy Agency, Tokai, Ibaraki (Japan); Ozawa, A.; Ishibashi, Y. [University of Tsukuba, Institute of Physics, Tsukuba, Ibaraki (Japan); Moriguchi, T. [National Cerebral and Cardiovascular Center Research Institute, Suita, Osaka (Japan); Yamaguchi, H.; Kahl, D. [University of Tokyo, Wako Branch, Center for Nuclear Study (CNS), Wako, Saitama (Japan); Hayakawa, S. [Laboratori Nazionali del Sud-INFN, Catania (Italy); Nguyen Binh, Dam [Vietnamese Academy for Science and Technology, Institute of Physics, Hanoi (Viet Nam); Chen, A.A.; Chen, J. [McMaster University, Hamilton, Ontario (Canada); Setoodehnia, K. [University of Notre Dame, Department of Physics, Notre Dame, Indiana (United States); Kajino, T. [National Astronomical Observatory, Tokyo (Japan); University of Tokyo, Department of Astronomy, Graduate School of Science, Tokyo (Japan)

2014-09-15

The level scheme above the proton threshold in {sup 26}Si is crucial for evaluating the {sup 25}Al(p, γ){sup 26}Si stellar reaction, which is important for understanding the astrophysical origin of the long-lived cosmic radioactivity {sup 26}Al(T{sub 1/2} = 7.17 x 10{sup 5} y) in the Galaxy. The excited states in {sup 26}Si have been studied using an in-beam γ-ray spectroscopy technique with the {sup 24}Mg({sup 3}He, nγ){sup 26}Si reaction. γ-rays with energies up to 4.6 MeV emitted from excited states in {sup 26}Si have been measured using large volume HPGe detectors. The spin-parity of one of the most important states reported recently at 5890.0keV has been assigned as 0{sup +} by γ-γ angular correlation measurements in this work. (orig.)

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.

Pressure dependence of excited-state charge-carrier dynamics in organolead tribromide perovskites

Science.gov (United States)

Liu, X. C.; Han, J. H.; Zhao, H. F.; Yan, H. C.; Shi, Y.; Jin, M. X.; Liu, C. L.; Ding, D. J.

2018-05-01

Excited-state charge-carrier dynamics governs the performance of organometal trihalide perovskites (OTPs) and is strongly influenced by the crystal structure. Characterizing the excited-state charge-carrier dynamics in OTPs under high pressure is imperative for providing crucial insights into structure-property relations. Here, we conduct in situ high-pressure femtosecond transient absorption spectroscopy experiments to study the excited-state carrier dynamics of CH3NH3PbBr3 (MAPbBr3) under hydrostatic pressure. The results indicate that compression is an effective approach to modulate the carrier dynamics of MAPbBr3. Across each pressure-induced phase, carrier relaxation, phonon scattering, and Auger recombination present different pressure-dependent properties under compression. Responsiveness is attributed to the pressure-induced variation in the lattice structure, which also changes the electronic band structure. Specifically, simultaneous prolongation of carrier relaxation and Auger recombination is achieved in the ambient phase, which is very valuable for excess energy harvesting. Our discussion provides clues for optimizing the photovoltaic performance of OTPs.

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

A conceptual design of the set-up for solid state spectroscopy with free electron laser and insertion device radiation

CERN Document Server

Makhov, V N

2001-01-01

The set-up for complex solid state spectroscopy with the use of enhanced properties of radiation from insertion devices and free electron lasers is proposed. Very high flux and pulsed properties of radiation from insertion devices and free electron lasers offer the possibility for the use of such powerful techniques as electron paramagnetic resonance (EPR) and optically detected magnetic resonance (ODMR) for the studies of excited states of electronic excitations or defects in solids. The power density of radiation can become high enough for one more method of exited-state spectroscopy: transient optical absorption spectroscopy. The set-up is supposed to combine the EPR/ODMR spectrometer, i.e. cryostat supplied with superconducting magnet and microwave system, and the optical channels for excitation (by radiation from insertion devices or free electron laser) and detection of luminescence (i.e. primary and secondary monochromators). The set-up can be used both for 'conventional' spectroscopy of solids (reflec...

An excited state underlies gene regulation of a transcriptional riboswitch

Science.gov (United States)

Zhao, Bo; Guffy, Sharon L.; Williams, Benfeard; Zhang, Qi

2017-01-01

Riboswitches control gene expression through ligand-dependent structural rearrangements of the sensing aptamer domain. However, we found that the Bacillus cereus fluoride riboswitch aptamer adopts identical tertiary structures in solution with and without ligand. Using chemical exchange saturation transfer (CEST) NMR spectroscopy, we revealed that the structured ligand-free aptamer transiently accesses a low-populated (~1%) and short-lived (~3 ms) excited conformational state that unravels a conserved ‘linchpin’ base pair to signal transcription termination. Upon fluoride binding, this highly localized fleeting process is allosterically suppressed to activate transcription. We demonstrated that this mechanism confers effective fluoride-dependent gene activation over a wide range of transcription rates, which is essential for robust toxicity response across diverse cellular conditions. These results unveil a novel switching mechanism that employs ligand-dependent suppression of an aptamer excited state to coordinate regulatory conformational transitions rather than adopting distinct aptamer ground-state tertiary architectures, exemplifying a new mode of ligand-dependent RNA regulation. PMID:28719589

Rotational Spectra in 29 Vibrationally Excited States of Interstellar Aminoacetonitrile

Energy Technology Data Exchange (ETDEWEB)

Kolesniková, L.; Alonso, E. R.; Mata, S.; Alonso, J. L. [Grupo de Espectroscopia Molecular (GEM), Edificio Quifima, Área de Química-Física, Laboratorios de Espectroscopia y Bioespectroscopia, Parque Científico UVa, Unidad Asociada CSIC, Universidad de Valladolid, E-47011 Valladolid (Spain)

2017-04-01

We report a detailed spectroscopic investigation of the interstellar aminoacetonitrile, a possible precursor molecule of glycine. Using a combination of Stark and frequency-modulation microwave and millimeter wave spectroscopies, we observed and analyzed the room-temperature rotational spectra of 29 excited states with energies up to 1000 cm{sup −1}. We also observed the {sup 13}C isotopologues in the ground vibrational state in natural abundance (1.1%). The extensive data set of more than 2000 new rotational transitions will support further identifications of aminoacetonitrile in the interstellar medium.

Spectroscopy of nitrophenolates in vacuo: effect of spacer, configuration, and microsolvation on the charge-transfer excitation energy.

Science.gov (United States)

Brøndsted Nielsen, Steen; Brøndsted Nielsen, Mogens; Rubio, Angel

2014-04-15

In a charge-transfer (CT) transition, electron density moves from one end of the molecule (donor) to the other end (acceptor). This type of transition is of paramount importance in nature, for example, in photosynthesis, and it governs the excitation of several protein biochromophores and luminophores such as the oxyluciferin anion that accounts for light emission from fireflies. Both transition energy and oscillator strength are linked to the coupling between the donor and acceptor groups: The weaker the coupling, the smaller the excitation energy. But a weak coupling necessarily also causes a low oscillator strength possibly preventing direct excitation (basically zero probability in the noncoupling case). The coupling is determined by the actual spacer between the two groups, and whether the spacer acts as an insulator or a conductor. However, it can be difficult or even impossible to distinguish the effect of the spacer from that of local solvent molecules that often cause large solvent shifts due to different ground-state and excited-state stabilization. This calls for gas-phase spectroscopy experiments where absorption by the isolated molecule is identified to unequivocally establish the intrinsic molecular properties with no perturbations from a microenvironment. From such insight, the effect of a protein microenvironment on the CT excited state can be deduced. In this Account, we review our results over the last 5 years from mass spectroscopy experiments using specially designed apparatus on several charged donor-acceptor ions that are based on the nitrophenolate moiety and π-extended derivatives, which are textbook examples of donor-acceptor chromophores. The phenolate oxygen is the donor, and the nitro group is the acceptor. The choice of this system is also based on the fact that phenolate is a common structural motif of biochromophores and luminophores, for example, it is a constituent of the oxyluciferin anion. A presentation of the setups used for

Ultrafast S1 and ICT state dynamics of a marine carotenoid probed by femtosecond one- and two-photon pump-probe spectroscopy

International Nuclear Information System (INIS)

Kosumi, Daisuke; Kusumoto, Toshiyuki; Fujii, Ritsuko; Sugisaki, Mitsuru; Iinuma, Yoshiro; Oka, Naohiro; Takaesu, Yuki; Taira, Tomonori; Iha, Masahiko; Frank, Harry A.; Hashimoto, Hideki

2011-01-01

Ultrafast relaxation kinetics of fucoxanthin in polar and non-polar solvents have been studied by femtosecond pump-probe spectroscopy. Transient absorption associated with S 1 or intramolecular charge transfer (ICT) excited state has been observed following either one-photon excitation to the optically allowed S 2 state or two-photon excitation to the symmetry-forbidden S 1 state. The results suggest that the ICT state formed after excitation of fucoxanthin in a polar solvent is a distinct excited state from S 1 .

Excited-state intramolecular proton transfer of 2-acetylindan-1,3-dione studied by ultrafast absorption and fluorescence spectroscopy

Directory of Open Access Journals (Sweden)

Pramod Kumar Verma

2016-03-01

Full Text Available We employ transient absorption from the deep-UV to the visible region and fluorescence upconversion to investigate the photoinduced excited-state intramolecular proton-transfer dynamics in a biologically relevant drug molecule, 2-acetylindan-1,3-dione. The molecule is a ß-diketone which in the electronic ground state exists as exocyclic enol with an intramolecular H-bond. Upon electronic excitation at 300 nm, the first excited state of the exocyclic enol is initially populated, followed by ultrafast proton transfer (≈160 fs to form the vibrationally hot endocyclic enol. Subsequently, solvent-induced vibrational relaxation takes place (≈10 ps followed by decay (≈390 ps to the corresponding ground state.

Near-infrared spectroscopy (NIRS - electroencephalography (EEG based brain-state dependent electrotherapy (BSDE: A computational approach based on excitation-inhibition balance hypothesis

Directory of Open Access Journals (Sweden)

Snigdha Dagar

2016-08-01

Full Text Available Stroke is the leading cause of severe chronic disability and the second cause of death worldwide with 15 million new cases and 50 million stroke survivors. The post stroke chronic disability may be ameliorated with early neuro rehabilitation where non-invasive brain stimulation (NIBS techniques can be used as an adjuvant treatment to hasten the effects. However, the heterogeneity in the lesioned brain will require individualized NIBS intervention where innovative neuroimaging technologies of portable electroencephalography (EEG and functional-near-infrared spectroscopy (fNIRS can be leveraged for Brain State Dependent Electrotherapy (BSDE. In this hypothesis and theory article, we propose a computational approach based on excitation-inhibition (E-I balance hypothesis to objectively quantify the post stroke individual brain state using online fNIRS-EEG joint imaging. One of the key events that occurs following Stroke is the imbalance in local excitation-inhibition (that is the ratio of Glutamate/GABA which may be targeted with NIBS using a computational pipeline that includes individual forward models to predict current flow patterns through the lesioned brain or brain target region. The current flow will polarize the neurons which can be captured with excitation-inhibition based brain models. Furthermore, E-I balance hypothesis can be used to find the consequences of cellular polarization on neuronal information processing which can then be implicated in changes in function. We first review evidence that shows how this local imbalance between excitation-inhibition leading to functional dysfunction can be restored in targeted sites with NIBS (Motor Cortex, Somatosensory Cortex resulting in large scale plastic reorganization over the cortex, and probably facilitating recovery of functions. Secondly, we show evidence how BSDE based on inhibition–excitation balance hypothesis may target a specific brain site or network as an adjuvant treatment

A study of the excited 1Σ+sub(g) states in Na2

International Nuclear Information System (INIS)

Taylor, A.J.; Jones, K.M.; Schawlow, A.L.

1981-01-01

Using the technique of two-step polarization labeling spectroscopy seven excited 1 Σ + sub(g) states in Na 2 have been found. Molecular constants are derived from a Dunham expansion. Tentative assignments are made to the 3p + 3p, 3s + nd and 3s + ns atomic asymptotes. (orig.)

Ligand manipulation of charge transfer excited state relaxation and spin crossover in [Fe(2,2′-bipyridine)₂(CN)₂

DEFF Research Database (Denmark)

Kjær, Kasper Skov; Zhang, Wenkai; Alonso-Mori, Roberto

2017-01-01

We have used femtosecond resolution UV-visible and Kβ x-ray emission spectroscopy to characterize the electronic excited state dynamics of [Fe(bpy)2(CN)2], where bpy=2,2′-bipyridine, initiated by metal-to-ligand charge transfer (MLCT) excitation. The excited-state absorption in the transient UV-visible...

Continuous Flow-Resonance Raman Spectroscopy of an Intermediate Redox State of Cytochrome-C

DEFF Research Database (Denmark)

Forster, M.; Hester, R. E.; Cartling, B.

1982-01-01

An intermediate redox state of cytochrome c at alkaline pH, generated upon rapid reduction by sodium dithionite, has been observed by resonance Raman (RR) spectroscopy in combination with the continuous flow technique. The RR spectrum of the intermediate state is reported for excitation both...... in the (alpha, beta) and the Soret optical absorption band. The spectra of the intermediate state are more like those of the stable reduced form than those of the stable oxidized form. For excitation of 514.5 nm, the most prominent indication of an intermediate state is the wave-number shift of one RR band from...... 1,562 cm-1 in the stable oxidized state through 1,535 cm-1 in the intermediate state to 1,544 cm-1 in the stable reduced state. For excitation at 413.1 nm, a band, present at 1,542 cm-1 in the stable reduced state but not present in the stable oxidized state, is absent in the intermediate state. We...

Chemical modulation of electronic structure at the excited state

Science.gov (United States)

Li, F.; Song, C.; Gu, Y. D.; Saleem, M. S.; Pan, F.

2017-12-01

Spin-polarized electronic structures are the cornerstone of spintronics, and have thus attracted a significant amount of interest; in particular, researchers are looking into how to modulate the electronic structure to enable multifunctional spintronics applications, especially in half-metallic systems. However, the control of the spin polarization has only been predicted in limited two-dimensional systems with spin-polarized Dirac structures and is difficult to achieve experimentally. Here, we report the modulation of the electronic structure in the light-induced excited state in a typical half-metal, L a1 /2S r1 /2Mn O3 -δ . According to the spin-transport measurements, there appears a light-induced increase in magnetoresistance due to the enhanced spin scattering, which is closely associated with the excited spin polarization. Strikingly, the light-induced variation can be enhanced via alcohol processing and reduced by oxygen annealing. X-ray photoelectron spectroscopy measurements show that in the chemical process, a redox reaction occurs with a change in the valence of Mn. Furthermore, first-principles calculations reveal that the change in the valence of Mn alters the electronic structure and consequently modulates the spin polarization in the excited state. Our findings thus report a chemically tunable electronic structure, demonstrating interesting physics and the potential for multifunctional applications and ultrafast spintronics.

Electronic states of thiophene/phenylene co-oligomers: Extreme-ultra violet excited photoelectron spectroscopy observations and density functional theory calculations

International Nuclear Information System (INIS)

Kawaguchi, Yoshizo; Sasaki, Fumio; Mochizuki, Hiroyuki; Ishitsuka, Tomoaki; Tomie, Toshihisa; Ootsuka, Teruhisa; Watanabe, Shuji; Shimoi, Yukihiro; Yamao, Takeshi; Hotta, Shu

2013-01-01

We have investigated electronic states in the valence electron bands for the thin films of three thiophene/phenylene co-oligomer (TPCO) compounds, 2,5-bis(4-biphenylyl)thiophene (BP1T), 1,4-bis(5-phenylthiophen-2-yl)benzene (AC5), and 1,4-bis{5-[4-(trifluoromethyl)phenyl]thiophen-2-yl}benzene (AC5-CF 3 ), by using extreme-UV excited photoelectron spectroscopy (EUPS). By comparing both EUPS spectra and secondary electron spectra between AC5 and AC5-CF 3 , we confirm that CF 3 substitution to AC5 deepens valence states by 2 eV, and increases the ionization energy by 3 eV. From the cut-off positions of secondary electron spectra, the work functions of AC5, AC5-CF 3 , and BP1T are evaluated to be 3.8 eV, 4.8 eV, and 4.0 eV, respectively. We calculate molecular orbital (MO) energy levels by the density functional theory and compare results of calculations with those of experiments. Densities of states obtained by broadening MO levels well explain the overall features of experimental EUPS spectra of three TPCOs.

Dark excited states of carotenoid in light harvesting complex probing with femtosecond stimulated Raman spectroscopy

Directory of Open Access Journals (Sweden)

Sakai S.

2013-03-01

Full Text Available Vibrational dynamics of dark excited states in carotenoids have been investigated using tunable Raman pump pulses. The S1 state has same vibrational dynamics in light-harvesting complex (LH1 and solution. The S* state in LH1 has similar vibrational modes with the triplet state of carotenoid. However, the so-called S* state in solution does not have the modes and is concluded to be different from the S* state in LH1.

Ethanol- and trifluoroethanol-induced changes in phase states of DPPC membranes. Prodan emission-excitation fluorescence spectroscopy supported by PARAFAC analysis

Science.gov (United States)

Horochowska, Martyna; Cieślik-Boczula, Katarzyna; Rospenk, Maria

2018-03-01

It has been shown that Prodan emission-excitation fluorescence spectroscopy supported by Parallel Factor (PARAFAC) analysis is a fast, simple and sensitive method used in the study of the phase transition from the noninterdigitated gel (Lβ‧) state to the interdigitated gel (LβI) phase, triggered by ethanol and 2,2,2-trifluoroethanol (TFE) molecules in dipalmitoylphosphatidylcholines (DPPC) membranes. The relative contribution of lipid phases with spectral characteristics of each pure phase component has been presented as a function of an increase in alcohol concentration. It has been stated that both alcohol molecules can induce a formation of the LβI phase, but TFE is over six times stronger inducer of the interdigitated phase in DPPC membranes than ethanol molecules. Moreover, in the TFE-mixed DPPC membranes, the transition from the Lβ‧ to LβI phase is accompanied by a formation of the fluid phase, which most probably serves as a boundary phase between the Lβ‧ and LβI regions. Contrary to the three phase-state model of TFE-mixed DPPC membranes, in ethanol-mixed DPPC membranes only the two phase-state model has been detected.

Ultrafast S{sub 1} and ICT state dynamics of a marine carotenoid probed by femtosecond one- and two-photon pump-probe spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Kosumi, Daisuke, E-mail: kosumi@sci.osaka-cu.ac.j [CREST/JST and Department of Physics, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 (Japan); Kusumoto, Toshiyuki [CREST/JST and Department of Physics, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 (Japan); Fujii, Ritsuko; Sugisaki, Mitsuru [CREST/JST and Department of Physics, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 (Japan); Osaka City University Advanced Research Institute for Natural Science and Technology (OCARINA), Osaka (Japan); Iinuma, Yoshiro; Oka, Naohiro; Takaesu, Yuki; Taira, Tomonori; Iha, Masahiko [South Product Co. Ltd., 12-75 Suzaki, Uruma-shi, Okinawa 904-2234 (Japan); Frank, Harry A. [Department of Chemistry, University of Connecticut, Storrs, CT 06269-3060 (United States); Hashimoto, Hideki, E-mail: hassy@sci.osaka-cu.ac.j [CREST/JST and Department of Physics, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585 (Japan); Osaka City University Advanced Research Institute for Natural Science and Technology (OCARINA), Osaka (Japan)

2011-03-15

Ultrafast relaxation kinetics of fucoxanthin in polar and non-polar solvents have been studied by femtosecond pump-probe spectroscopy. Transient absorption associated with S{sub 1} or intramolecular charge transfer (ICT) excited state has been observed following either one-photon excitation to the optically allowed S{sub 2} state or two-photon excitation to the symmetry-forbidden S{sub 1} state. The results suggest that the ICT state formed after excitation of fucoxanthin in a polar solvent is a distinct excited state from S{sub 1}.

Photoluminescence excitation spectroscopy of SiV- and GeV- color center in diamond

Science.gov (United States)

Häußler, Stefan; Thiering, Gergő; Dietrich, Andreas; Waasem, Niklas; Teraji, Tokuyuki; Isoya, Junichi; Iwasaki, Takayuki; Hatano, Mutsuko; Jelezko, Fedor; Gali, Adam; Kubanek, Alexander

2017-06-01

Color centers in diamond are important quantum emitters for a broad range of applications ranging from quantum sensing to quantum optics. Understanding the internal energy level structure is of fundamental importance for future applications. We experimentally investigate the level structure of an ensemble of few negatively charged silicon-vacancy (SiV-) and germanium-vacancy (GeV-) centers in bulk diamond at room temperature by photoluminescence (PL) and excitation (PLE) spectroscopy over a broad wavelength range from 460 to 650 {nm} and perform power-dependent saturation measurements. For SiV- our experimental results confirm the presence of a higher energy transition at ˜ 2.31 {eV}. By comparison with detailed theoretical simulations of the imaginary dielectric function we interpret the transition as a dipole-allowed transition from {}2{E}g-state to {}2{A}2u-state where the corresponding a 2u -level lies deeply inside the diamond valence band. Therefore, the transition is broadened by the diamond band. At higher excitation power of 10 {mW} we indicate signs of a parity-conserving transition at ˜ 2.03 {eV} supported by saturation measurements. For GeV- we demonstrate that the PLE spectrum is in good agreement with the mirror image of the PL spectrum of the zero-phonon line. Experimentally we do not observe a higher lying energy level up to a transition wavelength of 460 {nm}. The observed PL spectra are identical, independent of excitation wavelength, suggesting a rapid decay to {}2{E}u excited state and followed by optical transition to {}2{E}g ground state. Our investigations convey important insights for future quantum optics and quantum sensing experiments based on SiV--center and GeV--center in diamond.

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.

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.)

Extended Lagrangian Excited State Molecular Dynamics.

Science.gov (United States)

Bjorgaard, J A; Sheppard, D; Tretiak, S; Niklasson, A M N

2018-02-13

An extended Lagrangian framework for excited state molecular dynamics (XL-ESMD) using time-dependent self-consistent field theory is proposed. The formulation is a generalization of the extended Lagrangian formulations for ground state Born-Oppenheimer molecular dynamics [Phys. Rev. Lett. 2008 100, 123004]. The theory is implemented, demonstrated, and evaluated using a time-dependent semiempirical model, though it should be generally applicable to ab initio theory. The simulations show enhanced energy stability and a significantly reduced computational cost associated with the iterative solutions of both the ground state and the electronically excited states. Relaxed convergence criteria can therefore be used both for the self-consistent ground state optimization and for the iterative subspace diagonalization of the random phase approximation matrix used to calculate the excited state transitions. The XL-ESMD approach is expected to enable numerically efficient excited state molecular dynamics for such methods as time-dependent Hartree-Fock (TD-HF), Configuration Interactions Singles (CIS), and time-dependent density functional theory (TD-DFT).

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

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....

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....

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.

Product state resolved excitation spectroscopy of He-, Ne-, and Ar-Br2 linear isomers: experiment and theory.

Science.gov (United States)

Pio, Jordan M; van der Veer, Wytze E; Bieler, Craig R; Janda, Kenneth C

2008-04-07

Valence excitation spectra for the linear isomers of He-, Ne-, and Ar-Br2 are reported and compared to a two-dimensional simulation using the currently available potential energy surfaces. Excitation spectra from the ground electronic state to the region of the inner turning point of the Rg-Br2 (B,nu') stretching coordinate are recorded while probing the asymptotic Br2 (B,nu') state. Each spectrum is a broad continuum extending over hundreds of wavenumbers, becoming broader and more blueshifted as the rare gas atom is changed from He to Ne to Ar. In the case of Ne-Br2, the threshold for producing the asymptotic product state reveals the X-state linear isomer bond energy to be 71+/-3 cm(-1). The qualitative agreement between experiment and theory shows that the spectra can be correctly regarded as revealing the one-atom solvent shifts and also provides new insight into the one-atom cage effect on the halogen vibrational relaxation. The measured spectra provide data to test future ab initio potential energy surfaces in the interaction of rare gas atoms with the halogen valence excited state.

Quanty for core level spectroscopy - excitons, resonances and band excitations in time and frequency domain

International Nuclear Information System (INIS)

Haverkort, Maurits W.

2016-01-01

Depending on the material and edge under consideration, core level spectra manifest themselves as local excitons with multiplets, edge singularities, resonances, or the local projected density of states. Both extremes, i.e., local excitons and non-interacting delocalized excitations are theoretically well under control. Describing the intermediate regime, where local many body interactions and band-formation are equally important is a challenge. Here we discuss how Quanty , a versatile quantum many body script language, can be used to calculate a variety of different core level spectroscopy types on solids and molecules, both in the frequency as well as the time domain. The flexible nature of Quanty allows one to choose different approximations for different edges and materials. For example, using a newly developed method merging ideas from density renormalization group and quantum chemistry [1-3], Quanty can calculate excitons, resonances and band-excitations in x-ray absorption, photoemission, x-ray emission, fluorescence yield, non-resonant inelastic x-ray scattering, resonant inelastic x-ray scattering and many more spectroscopy types. Quanty can be obtained from: http://www.quanty.org. (paper)

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

Electronically excited states of chloroethylenes: Experiment and DFT calculations in comparison

International Nuclear Information System (INIS)

Khvostenko, O.G.

2014-01-01

Highlights: • B3LYP/6-311 + G(d,p) calculations of chloroethylenes molecules were performed. • Calculations were correlated with experiment on the molecules ground and excited states. • The general pattern of electron structure of chloroethylenes was obtained. • Necessity of this data for chloroethylenes negative ions study was noted. - Abstract: B3LYP/6-311 + G(d,p) calculations of ground and electronically excited states of ethylene, chloroethylene, 1,1-dichloroethylene, 1,2-dichloroethylene-cis, 1,2-dichloroethylene-trans trichloroethylene and tetrachloroethylene molecules have been performed. Molecular orbitals images and orbital correlation diagram are given. The calculation results for chloroethylenes electronically excited states were compared with experimental data from the energy-loss spectra obtained and generally considered previously by C.F. Koerting, K.N. Walzl and A. Kupperman. Several new additional triplet and singlet transitions were pointed out in these spectra considering the calculation results. The finding of the additional transitions was supported by the UV absorption spectrum of trichloroethylene recorded in big cuvette (10 cm), where the first three triplet and two low-intensive forbidden singlet transitions were registered. The first triplet of this compound was recorded to be at the same energy as was found with the energy-loss spectroscopy

Electronically excited states of chloroethylenes: Experiment and DFT calculations in comparison

Energy Technology Data Exchange (ETDEWEB)

Khvostenko, O.G., E-mail: khv@mail.ru

2014-08-15

Highlights: • B3LYP/6-311 + G(d,p) calculations of chloroethylenes molecules were performed. • Calculations were correlated with experiment on the molecules ground and excited states. • The general pattern of electron structure of chloroethylenes was obtained. • Necessity of this data for chloroethylenes negative ions study was noted. - Abstract: B3LYP/6-311 + G(d,p) calculations of ground and electronically excited states of ethylene, chloroethylene, 1,1-dichloroethylene, 1,2-dichloroethylene-cis, 1,2-dichloroethylene-trans trichloroethylene and tetrachloroethylene molecules have been performed. Molecular orbitals images and orbital correlation diagram are given. The calculation results for chloroethylenes electronically excited states were compared with experimental data from the energy-loss spectra obtained and generally considered previously by C.F. Koerting, K.N. Walzl and A. Kupperman. Several new additional triplet and singlet transitions were pointed out in these spectra considering the calculation results. The finding of the additional transitions was supported by the UV absorption spectrum of trichloroethylene recorded in big cuvette (10 cm), where the first three triplet and two low-intensive forbidden singlet transitions were registered. The first triplet of this compound was recorded to be at the same energy as was found with the energy-loss spectroscopy.

Light emitting diode excitation emission matrix fluorescence spectroscopy.

Science.gov (United States)

Hart, Sean J; JiJi, Renée D

2002-12-01

An excitation emission matrix (EEM) fluorescence instrument has been developed using a linear array of light emitting diodes (LED). The wavelengths covered extend from the upper UV through the visible spectrum: 370-640 nm. Using an LED array to excite fluorescence emission at multiple excitation wavelengths is a low-cost alternative to an expensive high power lamp and imaging spectrograph. The LED-EEM system is a departure from other EEM spectroscopy systems in that LEDs often have broad excitation ranges which may overlap with neighboring channels. The LED array can be considered a hybrid between a spectroscopic and sensor system, as the broad LED excitation range produces a partially selective optical measurement. The instrument has been tested and characterized using fluorescent dyes: limits of detection (LOD) for 9,10-bis(phenylethynyl)-anthracene and rhodamine B were in the mid parts-per-trillion range; detection limits for the other compounds were in the low parts-per-billion range (LED-EEMs were analyzed using parallel factor analysis (PARAFAC), which allowed the mathematical resolution of the individual contributions of the mono- and dianion fluorescein tautomers a priori. Correct identification and quantitation of six fluorescent dyes in two to six component mixtures (concentrations between 12.5 and 500 ppb) has been achieved with root mean squared errors of prediction (RMSEP) of less than 4.0 ppb for all components.

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

The electronically excited states of LH2 complexes from Rhodopseudomonas acidophila strain 10050 studied by time-resolved spectroscopy and dynamic Monte Carlo simulations. II. Homo-arrays of LH2 complexes reconstituted into phospholipid model membranes.

Science.gov (United States)

Pflock, Tobias J; Oellerich, Silke; Krapf, Lisa; Southall, June; Cogdell, Richard J; Ullmann, G Matthias; Köhler, Jürgen

2011-07-21

We performed time-resolved spectroscopy on homoarrays of LH2 complexes from the photosynthetic purple bacterium Rhodopseudomonas acidophila. Variations of the fluorescence transients were monitored as a function of the excitation fluence and the repetition rate of the excitation. These parameters are directly related to the excitation density within the array and to the number of LH2 complexes that still carry a triplet state prior to the next excitation. Comparison of the experimental observations with results from dynamic Monte Carlo simulations for a model cluster of LH2 complexes yields qualitative agreement without the need for any free parameter and reveals the mutual relationship between energy transfer and annihilation processes.

A novel low cost pulse excitation source to study trap spectroscopy of persistent luminescent materials

Science.gov (United States)

Chandrasekhar, Ngangbam; Singh, Nungleppam Monorajan; Gartia, R. K.

2018-04-01

Luminescent techniques require one or the other source of excitations which may vary from high cost X-rays, γ-rays, β-rays etc. to low cost LED. Persistent luminescent materials or Glow-in-the-Dark phosphors are the optical harvesters which store the optical energy from day light illuminating a whole night. They are so sensitive that they can be excited even with the low light of firefly. Therefore, instead of using a high cost excitation source authors have developed a low cost functioning of excitation source controlling short pulses of LED to excite persistent phosphors with the aid of ExpEYES Junior (Hardware/software framework developed by IUAC, New Delhi). Using this, the authors have excited the sample under investigation upto 10 ms. Trap spectroscopy of the pre-excited sample with LED is studied using Thermoluminescence (TL) technique. In this communication, development of the excitation source is discussed and demonstrate the its usefulness in the study of trap spectroscopy of commercially available CaS:Eu2+, Sm3+. Trapping parameters are also evaluated using Computerized Glow Curve Deconvolution (CGCD) technique.

Electronic properties of excited states in single InAs quantum dots; Elektronische Struktur angeregter Zustaende einzelner InAs-Quantenpunkte

Energy Technology Data Exchange (ETDEWEB)

Warming, Till

2009-02-20

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 ({mu}PLE). One of the main difficulties using {mu}PLE to probe single QDs is the unambiguous assignment of the observed resonances in the spectrum to specific transitions. By comparing micro photoluminescence ({mu}PL) and {mu}PLE 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

Perpendicular State of an Electronically Excited Stilbene: Observation by Femtosecond-Stimulated Raman Spectroscopy.

Science.gov (United States)

Quick, Martin; Dobryakov, Alexander L; Ioffe, Ilya N; Granovsky, Alex A; Kovalenko, Sergey A; Ernsting, Nikolaus P

2016-10-20

In the photoisomerization path of stilbene, a perpendicular state P on the S 1 potential energy surface is expected just before internal conversion through a conical intersection S 1 /S 0 . For decades the observation of P was thwarted by a short lifetime τ P in combination with slow population flow over a barrier. But these limitations can be overcome by ethylenic substitution. Following optical excitation of trans-1,1'-dicyanostilbene, P is populated significantly (τ P = 27 ps in n-hexane) and monitored by an exited-state absorption band at 370 nm. Here we report stimulated Raman lines of P. The strongest, at 1558 cm -1 , is attributed to stretching vibrations of the phenyl rings. Transient electronic states, resonance conditions, and corresponding Raman signals are discussed.

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...

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

Molecular spectroscopy

International Nuclear Information System (INIS)

Kokh, Eh.; Zonntag, B.

1981-01-01

The latest investigation results on molecular spectroscopy with application of synchrotron radiation in the region of vacuum ultraviolet are generalized. Some results on investigation of excited, superexcited and ionized molecule states with the use of adsorption spectroscopy, photoelectron spectroscopy, by fluorescent and mass-spectrometric methods are considered [ru

Branching ratios in the radiative decay of helium doubly excited states

International Nuclear Information System (INIS)

Coreno, M.; Prince, K. C.; Richter, R.; De Simone, M.; Bucar, K.; Zitnik, M.

2005-01-01

The doubly excited singlet states of He below the N=2 threshold may decay by autoionization or fluorescence. In the fluorescence decay channel, most decay cascades consist of emission of three photons, of which the first is a VUV photon, the second is in or near the visible range, and the last is another VUV photon. We have studied the fluorescence channel decay dynamics of the (2,0 n ) (2,1 n ) and (2,-1 n ) 1 P, n=3-7, states by wavelength dispersed photon-induced fluorescence spectroscopy. We have detected the photons in the second step of the cascade and determined the branching ratios for the strongest lines in this step. From these data we are able to calculate the branching ratios of the first step in the cascade. The results are in good agreement with calculations of the main decay channels of the higher resonances, but about 20-30 % lower, and so we are able to describe quantitatively the whole fluorescence cascade of the above-mentioned doubly excited states

Spectral reconstruction for shifted-excitation Raman difference spectroscopy (SERDS).

Science.gov (United States)

Guo, Shuxia; Chernavskaia, Olga; Popp, Jürgen; Bocklitz, Thomas

2018-08-15

Fluorescence emission is one of the major obstacles to apply Raman spectroscopy in biological investigations. It is usually several orders more intense than Raman scattering and hampers further analysis. In cases where the fluorescence emission is too intense to be efficiently removed via routine mathematical baseline correction algorithms, an alternative approach is needed. One alternative approach is shifted-excitation Raman difference spectroscopy (SERDS), where two Raman spectra are recorded with two slightly different excitation wavelengths. Ideally, the fluorescence emission at the two excitations does not change while the Raman spectrum shifts according to the excitation wavelength. Hence the fluorescence is removed in the difference of the two recorded Raman spectra. For better interpretability a spectral reconstruction procedure is necessary to recover the fluorescence-free Raman spectrum. This is challenging due to the intensity variations between the two recorded Raman spectra caused by unavoidable experimental changes as well as the presence of noise. Existent approaches suffer from drawbacks like spectral resolution loss, fluorescence residual, and artefacts. In this contribution, we proposed a reconstruction method based on non-negative least squares (NNLS), where the intensity variations between the two measurements are utilized in the reconstruction model. The method achieved fluorescence-free reconstruction on three real-world SERDS datasets without significant information loss. Thereafter, we quantified the performance of the reconstruction based on artificial datasets from four aspects: reconstructed spectral resolution, precision of reconstruction, signal-to-noise-ratio (SNR), and fluorescence residual. The artificial datasets were constructed with varied Raman to fluorescence intensity ratio (RFIR), SNR, full-width at half-maximum (FWHM), excitation wavelength shift, and fluorescence variation between the two spectra. It was demonstrated that

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.)

Excited states rotational effects on the behavior of excited molecules

CERN Document Server

Lim, Edward C

2013-01-01

Excited States, Volume 7 is a collection of papers that discusses the excited states of molecules. The first paper reviews the rotational involvement in intra-molecular in vibrational redistribution. This paper analyzes the vibrational Hamiltonian as to its efficacy in detecting the manifestations of intra-molecular state-mixing in time-resolved and time-averaged spectroscopic measurements. The next paper examines the temporal behavior of intra-molecular vibration-rotation energy transfer (IVRET) and the effects of IVRET on collision, reaction, and the decomposition processes. This paper also

Fluorescence excitation involving multiple electron transition states of N{sub 2} and CO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Wu, C.Y.R.; Chen, F.Z.; Hung, T.; Judge, D.L. [Univ. of Southern California, Los Angeles, CA (United States)

1997-04-01

The electronic states and electronic structures of N{sub 2} and CO{sub 2} in the 8-50 eV energy region have been studied extensively both experimentally and theoretically. In the energy region higher than 25 eV there exists many electronic states including multiple electron transition (MET) states which are responsible for producing most of the dissociative photoionization products. The electronic states at energies higher than 50 eV have been mainly determined by Auger spectroscopy, double charge transfer, photofragment spectroscopy and ion-ion coincidence spectroscopy. The absorption and ionization spectra of these molecules at energies higher than 50 eV mainly show a monotonic decrease in cross section values and exhibit structureless features. The decay channels of MET and Rydberg (or superexcited) states include autoionization, ionization, dissociative ionization, predissociation, and dissociation while those of single ion and multiple ion states may involve predissociation. and dissociation processes. The study of fluorescence specifically probes electronically excited species resulting from the above-mentioned decay channels and provides information for understanding the competition among these channels.

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

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

Diode laser excited optogalvanic spectroscopy of glow discharges

International Nuclear Information System (INIS)

Barshick, C. M.; Shaw, R. W.; Jennings, L. W.; Post-Zwicker, A.; Young, J. P.; Ramsey, J. M.

1997-01-01

The development of diode-laser-excited isotopically-selective optogalvanic spectroscopy (OGS) of uranium metal, oxide and fluoride in a glow discharge (GD) is presented. The technique is useful for determining 235 U/( 235 U+ 238 U) isotope ratios in these samples. The precision and accuracy of this determination is evaluated, and a study of experimental parameters pertaining to optimization of the measurement is discussed. Application of GD-OGS to other f-transition elements is also described

Diode laser excited optogalvanic spectroscopy of glow discharges

International Nuclear Information System (INIS)

Barshick, C.M.; Shaw, R.W.; Post-Zwicker, A., Young, J.P.; Ramsey, J.M.

1996-01-01

The development of diode-laser-excited isotopically-selective optogalvanic spectroscopy (OGS) of uranium metal, oxide and fluoride in a glow discharge (GD) is presented. The technique is useful for determining isotopic ratios of 235 U/( 235 U + 238 U) in the above samples. The precision and accuracy of this determination is evaluated, and a study of experimental parameters pertaining to optimization of he measurement is discussed. Application of the GD-OGS to other f-transition elements is also described

Two-colour dip spectroscopy of jet-cooled molecules

Science.gov (United States)

Ito, Mitsuo

In optical-optical double resonance spectroscopy, the resonance transition from an intermediate state to a final state can be detected by a dip of the signal (fluorescence or ion) associated with the intermediate state. This method probing the signal of the intermediate state may be called `two-colour dip spectroscopy'. Various kinds of two-colour dip spectroscopy such as two-colour fluorescence/ion dip spectroscopy, two-colour ionization dip spectroscopy employing stimulated emission, population labelling spectroscopy and mass-selected ion dip spectroscopy with dissociation were briefly described, paying special attention to their characteristics in excitation, detection and application. They were extensively and successfully applied to jet-cooled large molecules and provided us with new useful information on the energy and dynamics of excited molecules.

Excitations and relaxation dynamics in multiferroic GeV4S8 studied by terahertz and dielectric spectroscopy

Science.gov (United States)

Reschke, S.; Wang, Zhe; Mayr, F.; Ruff, E.; Lunkenheimer, P.; Tsurkan, V.; Loidl, A.

2017-10-01

We report on THz time-domain spectroscopy on multiferroic GeV4S8 , which undergoes orbital ordering at a Jahn-Teller transition at 30.5 K and exhibits antiferromagnetic order below 14.6 K. The THz experiments are complemented by dielectric experiments at audio and radio frequencies. We identify a low-lying excitation close to 0.5 THz, which is only weakly temperature dependent and probably corresponds to a molecular excitation within the electronic level scheme of the V4 clusters. In addition, we detect complex temperature-dependent behavior of a low-lying phononic excitation, closely linked to the onset of orbitally driven ferroelectricity. In the high-temperature cubic phase, which is paramagnetic and orbitally disordered, this excitation is of relaxational character becomes an overdamped Lorentzian mode in the orbitally ordered phase below the Jahn-Teller transition, and finally appears as well-defined phonon excitation in the antiferromagnetic state. Abrupt changes in the real and imaginary parts of the complex dielectric permittivity show that orbital ordering appears via a structural phase transition with strong first-order character and that the onset of antiferromagnetic order is accompanied by significant structural changes, which are of first-order character, too. Dielectric spectroscopy documents that at low frequencies, significant dipolar relaxations are present in the orbitally ordered, paramagnetic phase only. In contrast to the closely related GaV4S8 , this relaxation dynamics that most likely mirrors coupled orbital and polar fluctuations does not seem to be related to the dynamic processes detected in the THz regime.

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

Ligand manipulation of charge transfer excited state relaxation and spin crossover in [Fe(2,2′-bipyridine2(CN2

Directory of Open Access Journals (Sweden)

Kasper S. Kjær

2017-07-01

Full Text Available We have used femtosecond resolution UV-visible and Kβ x-ray emission spectroscopy to characterize the electronic excited state dynamics of [Fe(bpy2(CN2], where bpy=2,2′-bipyridine, initiated by metal-to-ligand charge transfer (MLCT excitation. The excited-state absorption in the transient UV-visible spectra, associated with the 2,2′-bipyridine radical anion, provides a robust marker for the MLCT excited state, while the transient Kβ x-ray emission spectra provide a clear measure of intermediate and high spin metal-centered excited states. From these measurements, we conclude that the MLCT state of [Fe(bpy2(CN2] undergoes ultrafast spin crossover to a metal-centered quintet excited state through a short lived metal-centered triplet transient species. These measurements of [Fe(bpy2(CN2] complement prior measurement performed on [Fe(bpy3]2+ and [Fe(bpy(CN4]2− in dimethylsulfoxide solution and help complete the chemical series [Fe(bpyN(CN6–2N]2N-4, where N = 1–3. The measurements confirm that simple ligand modifications can significantly change the relaxation pathways and excited state lifetimes and support the further investigation of light harvesting and photocatalytic applications of 3d transition metal complexes.

Diode laser excited optogalvanic spectroscopy of glow discharges

International Nuclear Information System (INIS)

Barshick, C.M.; Shaw, R.W.; Jennings, L.W.; Post-Zwicker, A.; Young, J.P.; Ramsey, J.M.

1997-01-01

The development of diode-laser-excited isotopically-selective optogalvanic spectroscopy (OGS) of uranium metal, oxide and fluoride in a glow discharge (GD) is presented. The technique is useful for determining 235 U/( 235 U+ 238 U) isotope ratios in these samples. The precision and accuracy of this determination is evaluated, and a study of experimental parameters pertaining to optimization of the measurement is discussed. Application of GD-OGS to other f-transition elements is also described. copyright 1997 American Institute of Physics

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

Production of excited double hypernuclei via Fermi breakup of excited strange systems

International Nuclear Information System (INIS)

Sanchez Lorente, Alicia; Botvina, Alexander S.; Pochodzalla, Josef

2011-01-01

Precise spectroscopy of multi-strange hypernuclei provides a unique chance to explore the hyperon-hyperon interaction. In the present work we explore the production of excited states in double hypernuclei following the micro-canonical break-up of an initially excited double hypernucleus which is created by the absorption and conversion of a stopped Ξ - hyperon. Rather independent on the spectrum of possible excited states in the produced double hypernuclei the formation of excited states dominates in our model. For different initial target nuclei which absorb the Ξ - , different double hypernuclei nuclei dominate. Thus the ability to assign the various observable γ-transitions in a unique way to a specific double hypernuclei by exploring various light targets as proposed by the PANDA Collaboration seems possible. We also confront our predictions with the correlated pion spectra measured by the E906 Collaboration.

Interaction of VUV-photons with molecules. Spectroscopy and dynamics of molecular superexcited states

International Nuclear Information System (INIS)

Hatano, Y.

2002-01-01

Complete text of publication follows. A survey is given of recent progress in experimental studies of the interaction of VUV-photons with molecules, i.e., those of photoabsorption, photoionization, and photodissociation of molecules in the excitation photon energy range of 10-50 eV, with a particular emphasis placed on current understanding of the spectroscopy and dynamics of formed molecular superexcited states. These studies are of great importance in understanding the interaction of ionizing radiation with matter. Molecules studied are ranged from simple diatomic and triatomic molecules to polyatomic molecules such as hydrocarbons. Most of the observed molecular superexcited states are assigned to high Rydber states which are vibrationally, doubly, or inner-core excited and converge to each of ion states. Non-Rydberg superexcited states are also observed. Dissociation into neutral fragments in comparison with ionization is of unexpectedly great importance in the observed decay of each of these state-assigned superexcited molecules. Dissociation dynamics as well as its products of superexcited states are remarkably different from those of lower excited states below about ionization thresholds. Some remarks are also presented of molecules in the condensed phase

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

Progress in atomic spectroscopy

International Nuclear Information System (INIS)

Beyer, H.J.; Kleinpoppen, H.

1984-01-01

This book presents reviews by leading experts in the field covering areas of research at the forefront of atomic spectroscopy. Topics considered include the k ordering of atomic structure, multiconfiguration Hartree-Fock calculations for complex atoms, new methods in high-resolution laser spectroscopy, resonance ionization spectroscopy (inert atom detection), trapped ion spectroscopy, high-magnetic-field atomic physics, the effects of magnetic and electric fields on highly excited atoms, x rays from superheavy collision systems, recoil ion spectroscopy with heavy ions, investigations of superheavy quasi-atoms via spectroscopy of electron rays and positrons, impact ionization by fast projectiles, and amplitudes and state parameters from ion- and atom-atom excitation processes

Modeling the high-energy electronic state manifold of adenine: Calibration for nonlinear electronic spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Nenov, Artur, E-mail: Artur.Nenov@unibo.it; Giussani, Angelo; Segarra-Martí, Javier; Jaiswal, Vishal K. [Dipartimento di Chimica “G. Ciamician,” Università di Bologna, Via Selmi 2, IT-40126 Bologna (Italy); Rivalta, Ivan [Université de Lyon, CNRS, Institut de Chimie de Lyon, École Normale Supérieure de Lyon, 46 Allée d’Italie, F-69364 Lyon Cedex 07 (France); Cerullo, Giulio [Dipartimento di Fisica, Politecnico di Milano, IFN-CNR, Piazza Leonardo Da Vinci 32, IT-20133 Milano (Italy); Mukamel, Shaul [Department of Chemistry, University of California, Irvine, California 92697-2025 (United States); Garavelli, Marco, E-mail: marco.garavelli@unibo.it, E-mail: marco.garavelli@ens-lyon.fr [Dipartimento di Chimica “G. Ciamician,” Università di Bologna, Via Selmi 2, IT-40126 Bologna (Italy); Université de Lyon, CNRS, Institut de Chimie de Lyon, École Normale Supérieure de Lyon, 46 Allée d’Italie, F-69364 Lyon Cedex 07 (France)

2015-06-07

Pump-probe electronic spectroscopy using femtosecond laser pulses has evolved into a standard tool for tracking ultrafast excited state dynamics. Its two-dimensional (2D) counterpart is becoming an increasingly available and promising technique for resolving many of the limitations of pump-probe caused by spectral congestion. The ability to simulate pump-probe and 2D spectra from ab initio computations would allow one to link mechanistic observables like molecular motions and the making/breaking of chemical bonds to experimental observables like excited state lifetimes and quantum yields. From a theoretical standpoint, the characterization of the electronic transitions in the visible (Vis)/ultraviolet (UV), which are excited via the interaction of a molecular system with the incoming pump/probe pulses, translates into the determination of a computationally challenging number of excited states (going over 100) even for small/medium sized systems. A protocol is therefore required to evaluate the fluctuations of spectral properties like transition energies and dipole moments as a function of the computational parameters and to estimate the effect of these fluctuations on the transient spectral appearance. In the present contribution such a protocol is presented within the framework of complete and restricted active space self-consistent field theory and its second-order perturbation theory extensions. The electronic excited states of adenine have been carefully characterized through a previously presented computational recipe [Nenov et al., Comput. Theor. Chem. 1040–1041, 295-303 (2014)]. A wise reduction of the level of theory has then been performed in order to obtain a computationally less demanding approach that is still able to reproduce the characteristic features of the reference data. Foreseeing the potentiality of 2D electronic spectroscopy to track polynucleotide ground and excited state dynamics, and in particular its expected ability to provide

Excitation dynamics of dye doped tris(8-hydroxy quinoline) aluminum films studied using time-resolved photoelectron spectroscopy

International Nuclear Information System (INIS)

Read, K.; Karlsson, H. S.; Murnane, M. M.; Kapteyn, H. C.; Haight, R.

2001-01-01

In this work, we use excite-probe photoelectron spectroscopy to study the decay of electronic excitation in tris(8-hydroxy quinoline) aluminum (Alq) doped with the organic dye 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM). Ultrashort laser pulses are used to photoexcite electrons into unoccupied molecular orbitals, and the ensuing decay rate is directly observed using photoelectron spectroscopy. Decay of the electronic excitation is studied as a function of DCM doping percentage and excitation intensity. The decay rate is seen to increase with both doping percentage and excitation intensity. These data are explained using a model including Foerster transfer, stimulated emission, concentration quenching, and bimolecular singlet - singlet exciton annihilation. In this model, we find that it is necessary to include a very fast (faster than predicted in standard Foerster transfer theory) excitation transfer of a fraction of the excitation from the Alq to the DCM, where that fraction corresponds to the approximate nearest-neighbor population. [copyright] 2001 American Institute of Physics

Excited-state inter- and intramolecular proton transfer in methyl 3-hydroxy-2-quinoxalinate: effects of solvent and acid or base concentrations

International Nuclear Information System (INIS)

Dogra, S.K.

2005-01-01

Absorption, fluorescence excitation and fluorescence spectroscopy, combined with time-dependent spectroscopy and semi-empirical (AM1) and density functional theory using Gaussian 98 program calculations have been used to study the effects of solvent and acid or base concentration on the spectral characteristics of methyl 3-hydroxy-2-quinoxalinate (M3HQ). M3HQ is present as enol in less polar solvents and as keto in polar media. In non-polar solvents, large Stokes shifted fluorescence band is assigned to the phototautomer, formed by the excited-state intramolecular proton transfer, whereas fluorescence is only observed from keto in the polar solvents. In aqueous and polar solvents the monocation (MC5/MC6) is formed by protonating the carbonyl oxygen atom in the ground (S 0 ) and the first excited singlet states (S 1 ). Dication is formed by protonating one of ?N- atom of MC5/MC6. Monoanion is formed by deprotonating the phenolic proton of enol in the basic solution. pK a values for different prototropic equilibriums were determined in S 0 and S 1 states and discussed

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...

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

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....

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.)

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.

Relaxation of excited surface states of thin Ge-implanted silica films probed by OSEE spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Zatsepin, A.F., E-mail: a.f.zatsepin@urfu.ru [Ural Federal University, Mira Street 19, 620002 Ekaterinburg (Russian Federation); Buntov, E.A.; Mikhailovich, A.P.; Slesarev, A.I. [Ural Federal University, Mira Street 19, 620002 Ekaterinburg (Russian Federation); Schmidt, B. [Research Center Dresden-Rossendorf, Institute of Ion Beam Physics and Materials Research, P.O. Box 510119, D-01314 Dresden (Germany); Czarnowski, A. von; Fitting, Hans-Joachim [Institute of Physics, University of Rostock, Universitätsplatz 3, D-18051 Rostock (Germany)

2016-01-15

As an example of thin silica films, 30 nm SiO{sub 2}–Si heterostructures implanted with Ge{sup +} ions (10{sup 16} cm{sup −2} fluence) and rapid thermally annealed (RTA) at 950 °C are studied by means of optically stimulated electron emission (OSEE) in the spectral region of optical transparency for bulk silica. Quartz glass samples were used as references. Experimental data revealed a strong dependence between electron emission spectral features and RTA annealing time. The spectral contributions of both surface band tail states and interband transitions were clearly distinguished. The application of emission Urbach rule as well as Kane and Pässler equations allowed to analyze the OSEE spectra at different optical excitation energy ranges and to retrieve the important microstructural and energy parameters. The observed correlations between parameter values of Urbach- and Kane-related models suggest the implantation-induced conversion of both the vibrational subsystem and energy band of surface and interface electronic states. - Highlights: • Peculiarities of electron emission from excited surface states of SiO{sub 2}:Ge structures are studied. • Spectral contributions of surface band tails and interband transitions are distinguished. • Urbach and Kane models allow to examine photo-thermal emission mechanism. • Surface energy gap and structural disorder parameters are determined.

Eu/RG absorption and excitation spectroscopy in the solid rare gases: state dependence of crystal field splitting and Jahn-Teller coupling.

Science.gov (United States)

Byrne, Owen; McCaffrey, John G

2011-03-28

Absorption spectroscopy recorded for annealed samples of matrix-isolated atomic europium reveals a pair of thermally stable sites in Ar and Kr while a single site exists in Xe. Plots of the matrix shifts of the visible s → p bands versus host polarizability, allowed the association of the single site in Xe and the blue sites in Ar and Kr. On the basis of the similar ground state bond lengths expected for the Eu-rare gas (RG) diatomics and the known Na-RG molecules, the blue sites are attributed to Eu occupancy in the smaller tetra-vacancy while the red sites are proposed to arise from hexa-vacancy sites. Both sites are of cubic symmetry, consistent with the pronounced Jahn-Teller structure present on the y(8)P ← a(8)S(7/2) transition for these bands in the three hosts studied. Site-selective excitation spectroscopy has been used to reanalyze complex absorption spectra previously published by Jakob et al. [Phys. Lett. A 57, 67 (1976)] for the near-UV f → d transitions. On the basis that a pair of thermally stable sites exist in solid argon, the occurrence of crystal field splitting has been identified to occur for the J ≥ 5/2 level of the (8)P state when isolated in these two sites with cubic symmetry. From a detailed lineshape analysis, the magnitude of the crystal field splittings on the J = 5/2 level in Ar is found to be 105 and 123 cm(-1) for the red and blue sites, respectively.

Laser excitation of 8-eV electronic states in Th{sup +}. A first pillar of the electronic bridge toward excitation of the Th-229 nucleus

Energy Technology Data Exchange (ETDEWEB)

Herrera-Sancho, Oscar-Andrey

2012-11-23

The possibility to realize a nuclear clock based on the optical magnetic dipole transition from the ground state to the low-energy isomeric state in the {sup 229}Th nucleus has motivated experiments and proposals toward highly accurate clocks with trapped ions and highly stable optical frequency standards with Th-doped solids. These systems hold great promise to open a field of research in the borderland between atomic and nuclear physics, which will enable highly sensitive tests of postulates from fundamental physics and also will allow us to coherently excite and control nuclear states, opening a wonderful and intriguing new field in physics. A major experimental obstacle that has to be overcome before any precision spectroscopy can be performed with this system is however the insufficient knowledge on the exact transition energy. The best experimental result so far is an indirect determination from {gamma}-spectroscopy with a relative uncertainty of about 6%. To facilitate the search for the nuclear transition within a wide uncertainty range around 8 eV, we investigate two-photon excitation in the dense electronic level structure of Th{sup +}, which enables the nuclear excitation via a resonantly enhanced inverse electronic bridge process. Experiments on one- and two-photon laser excitation of buffer gas cooled {sup 232}Th{sup +} ions in a radio-frequency ion trap are reported in this thesis. The strongest resonance line at 402 nm from the (6d{sup 2}7s)J=3/2 ground state to the (6d7s7p)J=5/2 state is driven as the first excitation step. Using nanosecond laser pulses in the 250-nm wavelength range for the second step of a two-photon excitation, we have observed seven previously unknown levels in the unexplored region of the electronic level structure around 8 eV. This investigation shows that the Th{sup +} ion seems to be well suited for the search of the isomer transition because both, theory and experimental results, agree on the density of strong transitions

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.

Excited meson spectroscopy with two chirally improved quarks

Science.gov (United States)

Engel, G.; Lang, C. B.; Mohler, D.; Limmer, M.; Schäfer, A.

The excited isovector meson spectrum is explored using two chirally improved dynamical quarks. Seven ensembles, with pion masses down to \\approx 250 MeV are discussed and used for extrapolations to the physical point. Strange mesons are investigated using partially quenched s-quarks. Using the variational method, we extract excited states in several channels and most of the results are in good agreement with experiment.

The electronically excited states of LH2 complexes from Rhodopseudomonas acidophila strain 10050 studied by time-resolved spectroscopy and dynamic Monte Carlo simulations. I. Isolated, non-interacting LH2 complexes.

Science.gov (United States)

Pflock, Tobias J; Oellerich, Silke; Southall, June; Cogdell, Richard J; Ullmann, G Matthias; Köhler, Jürgen

2011-07-21

We have employed time-resolved spectroscopy on the picosecond time scale in combination with dynamic Monte Carlo simulations to investigate the photophysical properties of light-harvesting 2 (LH2) complexes from the purple photosynthetic bacterium Rhodopseudomonas acidophila. The variations of the fluorescence transients were studied as a function of the excitation fluence, the repetition rate of the excitation and the sample preparation conditions. Here we present the results obtained on detergent solubilized LH2 complexes, i.e., avoiding intercomplex interactions, and show that a simple four-state model is sufficient to grasp the experimental observations quantitatively without the need for any free parameters. This approach allows us to obtain a quantitative measure for the singlet-triplet annihilation rate in isolated, noninteracting LH2 complexes.

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.

Atomic hydrogen and argon ground state density determination in a recombining plasma using visible light absorption spectroscopy

NARCIS (Netherlands)

Otorbaev, D.K.; Buuron, A.J.M.; Sanden, van de M.C.M.; Meulenbroeks, R.F.G.; Schram, D.C.

1995-01-01

The atomic radical density in the first excited state, obtained by the technique of optical absorption spectroscopy, and a simple kinetic model are used to determine the radical ground state density in a recombining expanding plasma. The kinetic model used does not require knowledge of the shape of

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.

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.

Selective Coherent Excitation of Charged Density Waves

NARCIS (Netherlands)

Tsvetkov, A.A.; Sagar, D.M.; Loosdrecht, P.H.M. van; Marel, D. van der

2003-01-01

Real time femtosecond pump-probe spectroscopy is used to study collective and single particle excitations in the charge density wave state of the quasi-1D metal, blue bronze. Along with the previously observed collective amplitudon excitation, the spectra show several additional coherent features.

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.

Laser-excited fluorescence spectroscopy of oxide glasses

International Nuclear Information System (INIS)

Weber, M.J.

1977-01-01

Laser-induced fluorescence line narrowing was applied to investigate the local fields and interactions of paramagnetic ions in oxide glasses. Studies included the site dependence of energy levels, radiative and nonradiative transition probabilities, homogeneous line broadening, and ion--ion energy transfer of rare earth ions. These results and the experimental techniques are reviewed briefly; the use of paramagnetic ions other than the rare earths is also considered. Recently, laser-excited fluorescence spectroscopy was used to investigate modifications in the local structure of lithium borate glass caused by compositional changes and phase separation and the site dependence of nonradiative relaxation of paramagnetic ions by multiphonon processes. These results and their implications are discussed. 6 figures

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

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.

Electron spectroscopy studies of argon K-shell excitation and vacancy cascades

International Nuclear Information System (INIS)

Southworth, S.H.; MacDonald, M.A.; LeBrun, T.; Azuma, Y.; Cooper, J.W.

1995-01-01

Electron spectroscopy combined with tunable synchrotron radiation has been used for studies of Ar K-shell excitation and vacancy decay processes. In addition, electrons and fluorescent X-rays have been recorded in coincidence to select subsets of the ejected electron spectra. Examples are presented for Ar 1s photoelectrons and KLL and LMM Auger spectra

Fluorescence excitation-emission matrix spectroscopy for degradation monitoring of machinery lubricants

Science.gov (United States)

Sosnovski, Oleg; Suresh, Pooja; Dudelzak, Alexander E.; Green, Benjamin

2018-02-01

Lubrication oil is a vital component of heavy rotating machinery defining the machine's health, operational safety and effectiveness. Recently, the focus has been on developing sensors that provide real-time/online monitoring of oil condition/lubricity. Industrial practices and standards for assessing oil condition involve various analytical methods. Most these techniques are unsuitable for online applications. The paper presents the results of studying degradation of antioxidant additives in machinery lubricants using Fluorescence Excitation-Emission Matrix (EEM) Spectroscopy and Machine Learning techniques. EEM Spectroscopy is capable of rapid and even standoff sensing; it is potentially applicable to real-time online monitoring.

Addressing the electronic properties of III–V nanowires by photoluminescence excitation spectroscopy

International Nuclear Information System (INIS)

De Luca, M

2017-01-01

Semiconductor nanowires (NWs) have been attracting an increasing interest in the scientific community. This is due to their peculiar filamentary shape and nanoscale diameter, which renders them versatile and cost-effective components of novel technological devices and also makes them an ideal platform for the investigation of a variety of fascinating physical effects. Absorption spectroscopy is a powerful and non-destructive technique able to provide information on the physical properties of the NWs. However, standard absorption spectroscopy is hard to perform in NWs, because of their small volume and the presence of opaque substrates. Here, we demonstrate that absorption can be successfully replaced by photoluminescence excitation (PLE). First, the use of polarization-resolved PLE to address the complex and highly-debated electronic band structure of wurtzite GaAs and InP NWs is shown. Then, PLE is used as a statistically-relevant method to localize the presence of separate wurtzite and zincblende NWs in the same InP sample. Finally, a variety of resonant exotic effects in the density of states of In x Ga 1−x As/GaAs core/shell NWs are highlighted by high-resolution PLE. (paper)

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.

Modeling of charge-transfer transitions and excited states in d6 transition metal complexes by DFT techniques

Czech Academy of Sciences Publication Activity Database

Vlček, Antonín; Záliš, Stanislav

2007-01-01

Roč. 251, 3-4 (2007), s. 258-287 ISSN 0010-8545 R&D Projects: GA MŠk 1P05OC068; GA MŠk OC 139 Institutional research plan: CEZ:AV0Z40400503 Keywords : charge-transfer transition * DFT technique * excited states * spectroscopy Subject RIV: CG - Electrochemistry Impact factor: 8.568, year: 2007

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.

Structural dynamics of phenylisothiocyanate in the light-absorbing excited states: Resonance Raman and complete active space self-consistent field calculation study

International Nuclear Information System (INIS)

Ouyang, Bing; Xue, Jia-Dan; Zheng, Xuming; Fang, Wei-Hai

2014-01-01

The excited state structural dynamics of phenyl isothiocyanate (PITC) after excitation to the light absorbing S 2 (A′), S 6 (A′), and S 7 (A′) excited states were studied by using the resonance Raman spectroscopy and complete active space self-consistent field method calculations. The UV absorption bands of PITC were assigned. The vibrational assignments were done on the basis of the Fourier transform (FT)-Raman and FT-infrared measurements, the density-functional theory computations, and the normal mode analysis. The A-, B-, and C-bands resonance Raman spectra in cyclohexane, acetonitrile, and methanol solvents were, respectively, obtained at 299.1, 282.4, 266.0, 252.7, 228.7, 217.8, and 208.8 nm excitation wavelengths to probe the corresponding structural dynamics of PITC. The results indicated that the structural dynamics in the S 2 (A′), S 6 (A′), and S 7 (A′) excited states were very different. The conical intersection point CI(S 2 /S 1 ) were predicted to play important role in the low-lying excited state decay dynamics. Two major decay channels were predicted for PITC upon excitation to the S 2 (A′) state: the radiative S 2,min → S 0 transition and the nonradiative S 2 → S 1 internal conversion via CI(S 2 /S 1 ). The differences in the decay dynamics between methyl isothiocyanate and PITC in the first light absorbing excited state were discussed. The role of the intersystem crossing point ISC(S 1 /T 1 ) in the excited state decay dynamics of PITC is evaluated

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.

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;

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

Molecular excitation dynamics and relaxation quantum theory and spectroscopy

CERN Document Server

Valkunas, Leonas; Mancal, Tomas

2013-01-01

Meeting the need for a work that brings together quantum theory and spectroscopy to convey excitation processes to advanced students and specialists wishing to conduct research and understand the entire field rather than just single aspects.Written by an experienced author and recognized authority in the field, this text covers numerous applications and offers examples taken from different disciplines. As a result, spectroscopists, molecular physicists, physical chemists, and biophysicists will all find this a must-have for their research. Also suitable as supplementary reading in graduate

Three-photon laser spectroscopy of even-parity bound states of samarium atom

International Nuclear Information System (INIS)

Gomonaj, O.Yi.; Kudelich, O.Yi.

2002-01-01

The energy spectrum of highly-excited even-parity bound states of a Sm atom, lying in the energy range 34421.1 - 36031.8 cm -1 , is investigated using three-photon resonance-ionization spectroscopy. The energies and total momenta of 48 levels are determined. Eight new levels not observed before are discovered. Thirteen intense two-photon transitions, which can be used in the schemes of Sm atom effective photoionization, are observed

Free electrons and ionic liquids: study of excited states by means of electron-energy loss spectroscopy and the density functional theory multireference configuration interaction method.

Science.gov (United States)

Regeta, Khrystyna; Bannwarth, Christoph; Grimme, Stefan; Allan, Michael

2015-06-28

The technique of low energy (0-30 eV) electron impact spectroscopy, originally developed for gas phase molecules, is applied to room temperature ionic liquids (IL). Electron energy loss (EEL) spectra recorded near threshold, by collecting 0-2 eV electrons, are largely continuous, assigned to excitation of a quasi-continuum of high overtones and combination vibrations of low-frequency modes. EEL spectra recorded by collecting 10 eV electrons show predominantly discrete vibrational and electronic bands. The vibrational energy-loss spectra correspond well to IR spectra except for a broadening (∼0.04 eV) caused by the liquid surroundings, and enhanced overtone activity indicating a contribution from resonant excitation mechanism. The spectra of four representative ILs were recorded in the energy range of electronic excitations and compared to density functional theory multireference configuration interaction (DFT/MRCI) calculations, with good agreement. The spectra up to about 8 eV are dominated by π-π* transitions of the aromatic cations. The lowest bands were identified as triplet states. The spectral region 2-8 eV was empty in the case of a cation without π orbitals. The EEL spectrum of a saturated solution of methylene green in an IL band showed the methylene green EEL band at 2 eV, indicating that ILs may be used as a host to study nonvolatile compounds by this technique in the future.

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

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.

Photophysical properties of 1-acetoxy-8-hydroxy-1,4,4a,9a-tetrahydroanthraquinone: Evidence for excited state proton transfer reaction

International Nuclear Information System (INIS)

Singh, Rupashree Balia; Mahanta, Subrata; Guchhait, Nikhil

2007-01-01

The photophysical properties of 1-acetoxy-8-hydroxy-1,4,4a,9a-tetrahydroanthraquinone (HTHQ) have been investigated by steady state and time resolved spectroscopy in combination with quantum chemical calculations. The effects of various parameters such as the nature of solvent and pH of the medium on the spectral properties confirm the existence of different neutral and ionic species in the ground and excited states. In the ground state, HTHQ exists as intramolecularly hydrogen bonded closed conformer in non-polar and polar aprotic solvents. Apart from the closed conformer, the intermolecular hydrogen bonded solvated species and the anion of HTHQ are present in hydroxylic solvents. The closed conformer shows excited state intramolecular proton transfer in all solvents and the solvent polarity independent red shifted emission indicates only keto-enol tautomerism. Evaluation of the potential energy surfaces by quantum chemical calculation using density functional theory point towards the possibility of proton transfer reaction in the first excited state but not in the ground state

Spectroscopy of dark soliton states in Bose-Einstein condensates

International Nuclear Information System (INIS)

Bongs, K; Burger, S; Hellweg, D; Kottke, M; Dettmer, S; Rinkleff, T; Cacciapuoti, L; Arlt, J; Sengstock, K; Ertmer, W

2003-01-01

Experimental and numerical studies of the velocity field of dark solitons in Bose-Einstein condensates are presented. The formation process after phase imprinting as well as the propagation of the emerging soliton are investigated using spatially resolved Bragg spectroscopy of soliton states in Bose-Einstein condensates of 87 Rb. A comparison of experimental data to results from numerical simulations of the Gross-Pitaevskii equation clearly identifies the flux underlying a dark soliton propagating in a Bose-Einstein condensate. The results allow further optimization of the phase imprinting method for creating collective excitations of Bose-Einstein condensates

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.

Spatially improved operators for excited hadrons on the lattice

International Nuclear Information System (INIS)

Burch, Tommy; Gattringer, Christof; Schaefer, Andreas; Glozman, Leonid Ya.; Kleindl, Reinhard; Lang, C.B.

2004-01-01

We present a new approach for determining spatially optimized operators that can be used for lattice spectroscopy of excited hadrons. Jacobi smeared quark sources with different widths are combined to construct hadron operators with different spatial wave functions. We use the variational method to determine those linear combinations of operators that have optimal overlap with ground and excited states. The details of the new approach are discussed and we demonstrate the power of the method using examples from quenched baryon and meson spectroscopy. In particular, we study the Roper state and ρ(1450) and discuss some physical implications of our tests

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.

Excited state electron and energy relays in supramolecular dinuclear complexes revealed by ultrafast optical and X-ray transient absorption spectroscopy.

Science.gov (United States)

Hayes, Dugan; Kohler, Lars; Hadt, Ryan G; Zhang, Xiaoyi; Liu, Cunming; Mulfort, Karen L; Chen, Lin X

2018-01-28

The kinetics of photoinduced electron and energy transfer in a family of tetrapyridophenazine-bridged heteroleptic homo- and heterodinuclear copper(i) bis(phenanthroline)/ruthenium(ii) polypyridyl complexes were studied using ultrafast optical and multi-edge X-ray transient absorption spectroscopies. This work combines the synthesis of heterodinuclear Cu(i)-Ru(ii) analogs of the homodinuclear Cu(i)-Cu(i) targets with spectroscopic analysis and electronic structure calculations to first disentangle the dynamics at individual metal sites by taking advantage of the element and site specificity of X-ray absorption and theoretical methods. The excited state dynamical models developed for the heterodinuclear complexes are then applied to model the more challenging homodinuclear complexes. These results suggest that both intermetallic charge and energy transfer can be observed in an asymmetric dinuclear copper complex in which the ground state redox potentials of the copper sites are offset by only 310 meV. We also demonstrate the ability of several of these complexes to effectively and unidirectionally shuttle energy between different metal centers, a property that could be of great use in the design of broadly absorbing and multifunctional multimetallic photocatalysts. This work provides an important step toward developing both a fundamental conceptual picture and a practical experimental handle with which synthetic chemists, spectroscopists, and theoreticians may collaborate to engineer cheap and efficient photocatalytic materials capable of performing coulombically demanding chemical transformations.

Tunable submillimeter sources applied to the excited state rotational spectroscopy and kinetics of CH3F

International Nuclear Information System (INIS)

Blumberg, W.A.M.; Fetterman, H.R.; Peck, D.D.; Goldsmith, P.F.

1979-01-01

Tunable submillimeter radiation, generated and detected using optically pumped lasers and Schottky diode mixers, has been used in an infrared-submillimeter double resonance investigation of CH 3 F. This technique permits the direct observation of the molecular rotational spectra and kinetics of excited vibrational states and is particularly important for those molecules which are candidates for optically pumped submillimeter lasers

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)

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

Ultrafast X-Ray Spectroscopy of Conical Intersections

Science.gov (United States)

Neville, Simon P.; Chergui, Majed; Stolow, Albert; Schuurman, Michael S.

2018-06-01

Ongoing developments in ultrafast x-ray sources offer powerful new means of probing the complex nonadiabatically coupled structural and electronic dynamics of photoexcited molecules. These non-Born-Oppenheimer effects are governed by general electronic degeneracies termed conical intersections, which play a key role, analogous to that of a transition state, in the electronic-nuclear dynamics of excited molecules. Using high-level ab initio quantum dynamics simulations, we studied time-resolved x-ray absorption (TRXAS) and photoelectron spectroscopy (TRXPS) of the prototypical unsaturated organic chromophore, ethylene, following excitation to its S2(π π*) state. The TRXAS, in particular, is highly sensitive to all aspects of the ensuing dynamics. These x-ray spectroscopies provide a clear signature of the wave packet dynamics near conical intersections, related to charge localization effects driven by the nuclear dynamics. Given the ubiquity of charge localization in excited state dynamics, we believe that ultrafast x-ray spectroscopies offer a unique and powerful route to the direct observation of dynamics around conical intersections.

The importance of spectroscopy for infrared multiphoton excitation

International Nuclear Information System (INIS)

Fuss, W.; Kompa, K.L.

1980-07-01

It is substantiated by examples that the infrared spectra of molecules in high vibrational states are similar in width to those of the ground states. Therefore in order to explain collisionless infrared multiphoton excitation, the existence of resonance has to be checked, not only for the first three steps, but for all of them. That is, their (low resolution) spectra should be studied. This review summarizes the spectroscopic mechanisms contributing to multiphoton excitation, which have been suggested to date, including several kinds of rotational compensation and of vibrational level splitting, which cooperate to overcome the anharmonic shift. The spectral quasicontinuum, generated by intensity borrowing, must neither be very broad nor dense, and collisionless vibrational relaxation is only important at very high energies. Knowledge of relatively few spectroscopic detailes helps to understand many details and many differences in multiphoton excitatio. (orig.)

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.

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

Photo-excited charge collection spectroscopy probing the traps in field-effect transistors

CERN Document Server

Im, Seongil; Kim, Jae Hoon

2013-01-01

Solid state field-effect devices such as organic and inorganic-channel thin-film transistors (TFTs) have been expected to promote advances in display and sensor electronics. The operational stabilities of such TFTs are thus important, strongly depending on the nature and density of charge traps present at the channel/dielectric interface or in the thin-film channel itself. This book contains how to characterize these traps, starting from the device physics of field-effect transistor (FET). Unlike conventional analysis techniques which are away from well-resolving spectral results, newly-introduced photo-excited charge-collection spectroscopy (PECCS) utilizes the photo-induced threshold voltage response from any type of working transistor devices with organic-, inorganic-, and even nano-channels, directly probing on the traps. So, our technique PECCS has been discussed through more than ten refereed-journal papers in the fields of device electronics, applied physics, applied chemistry, nano-devices and materia...

Studies on the substrate mediated vibrational excitation of CO/Si(100) by means of SFG spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Han, Xu; Lass, Kristian; Balgar, Thorsten; Hasselbrink, Eckart [Universitaet Duisburg-Essen, Fachbereich Chemie, 45117 Essen (Germany)

2009-07-01

Vibrational excitations of adsorbates play an important role in chemical reaction dynamics. In the past decade CO on solid surfaces was chosen as adequate model system for studying vibrational relaxation dynamics. Our work is focused on the energy dissipation of vibrationally excited CO adsorbed on a silicon surface by means of IR/Vis sum frequency generation (SFG) spectroscopy. Here we present studies on substrate mediated excitation of vibrational modes of CO on Si(100) induced by UV radiation. We suppose the observation of highly excited internal stretch vibrations of CO caused by hot electrons generated within the silicon substrate.

Ab initio interaction potentials for X and B excited states of He-I2 for studying dynamics

International Nuclear Information System (INIS)

Prosmiti, Rita; Garcia-Gutierrez, Leonor; Delgado-Tellez, Laura; Valdes, Alvaro; Villarreal, Pablo; Delgado-Barrio, Gerardo

2009-01-01

Ab initio CCSD(T) and MRCI approaches were employed to construct potential energy surfaces of the ground and the B electronic excited states of He-I 2 complex, while full quantum mechanical methods were applied to study its spectroscopy and dynamics. A description of the approach adopted, together with the results obtained and their comparison with recent experimental data, as well as further improvements are presented.

Nuclear Gamma-Ray Spectroscopy at the Limit of Particle Stability

International Nuclear Information System (INIS)

Dr. Norbert Pietralla

2006-01-01

The research project ''Nuclear Gamma-Ray Spectroscopy at the Limit of Particle Stability'' with sponsor ID ''DE-FG02-04ER41334'' started late-summer 2004 and aims at the investigation of highly excited low-spin states of selected key-nuclei in the vicinity of the particle separation threshold by means of high-resolution gamma-ray spectroscopy in electromagnetic excitation reactions. This work addresses nuclear structures with excitation energies close to the binding energy or highly excited off-yrast states in accordance with the NSAC milestones. In 2005 the program was extended towards additional use of virtual photons and theoretical description of the low-lying collective excitations in the well deformed nuclei

Luminescence and excited state dynamics in Bi{sup 3+}-doped LiLaP{sub 4}O{sub 12} phosphates

Energy Technology Data Exchange (ETDEWEB)

Babin, V. [Institute of Physics AS CR, Cukrovarnicka 10, 16200 Prague (Czech Republic); Chernenko, K., E-mail: nuclearphys@yandex.ru [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Peter the Great Saint-Petersburg Polytechnic University, Polytekhnicheskaya 29, 195251 St.Petersburg (Russian Federation); Demchenko, P. [Ivan Franko National University of Lviv, Kyryla i Mefodiya 8a, 79005 Lviv (Ukraine); Mihokova, E.; Nikl, M. [Institute of Physics AS CR, Cukrovarnicka 10, 16200 Prague (Czech Republic); Pashuk, I. [Ivan Franko National University of Lviv, Kyryla i Mefodiya 8a, 79005 Lviv (Ukraine); Shalapska, T. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia); Voloshinovskii, A. [Ivan Franko National University of Lviv, Kyryla i Mefodiya 8a, 79005 Lviv (Ukraine); Zazubovich, S. [Institute of Physics, University of Tartu, Ravila 14c, 50411 Tartu (Estonia)

2016-08-15

Photo- and X-ray-excited luminescence characteristics of Bi-doped LiLaP{sub 4}O{sub 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{sub 4}O{sub 12} phosphate. The broad 2.95 eV emission band of LiLaP{sub 4}O{sub 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{sup 3+} ion. No spectral bands are observed, arising from the electron transitions between the energy levels of Bi{sup 3+} ions. Phenomenological model is proposed for the description of the excited state dynamics of the Bi{sup 3+}-related localized exciton in LiLaP{sub 4}O{sub 12}:Bi and the parameters of the triplet localized exciton state are determined. Keywords: Photoluminescence; Time-resolved spectroscopy; Excited states; Bi{sup 3+} centers; LiLaP{sub 4}O{sub 12}:Bi powders.

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)

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

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)

Ultrafast Optical Excitation of a Persistent Surface-State Population in the Topological Insulator Bi2Se3

Energy Technology Data Exchange (ETDEWEB)

Sobota, Jonathan

2012-03-14

Using femtosecond time- and angle-resolved photoemission spectroscopy, we investigated the nonequilibrium dynamics of the topological insulator Bi{sub 2}Se{sub 3}. We studied p-type Bi{sub 2}Se{sub 3}, in which the metallic Dirac surface state and bulk conduction bands are unoccupied. Optical excitation leads to a meta-stable population at the bulk conduction band edge, which feeds a nonequilibrium population of the surface state persisting for >10 ps. This unusually long-lived population of a metallic Dirac surface state with spin texture may present a channel in which to drive transient spin-polarized currents.

The photoluminescence/excitation (PL/E) spectroscopy of Eu-implanted GaN

KAUST Repository

O'Donnell, Kevin Peter

2011-05-01

Several distinct luminescent centres form in GaN samples doped with Eu. One centre, Eu2, recently identified as the isolated, substitutional Eu impurity, EuGa, is dominant in ion-implanted samples annealed under very high pressures (1 GPa) of N2. According to structural determinations, such samples exhibit an essentially complete removal of lattice damage caused by the implantation process. A second centre, Eu1, probably comprising EuGa in association with an intrinsic lattice defect, produces a more complex emission spectrum. In addition there are several unidentified features in the 5D0 to 7F2 spectral region near 620 nm. We can readily distinguish Eu1 and Eu2 by their excitation spectra, in particular through their different sensitivities to above-gap and below-gap excitation. The present study extends recent work on photoluminescence/ excitation (PL/E) spectroscopy of Eu1 and Eu2 to arrive at an understanding of these mechanisms in terms of residual optically active defect concentrations. We also report further on the \\'host-independent\\' excitation mechanism that is active in the case of a prominent minority centre. The relevance of this work to the operation of the red GaN:Eu light-emitting diode is discussed. © 2010 Elsevier B.V. All rights reserved.

The photoluminescence/excitation (PL/E) spectroscopy of Eu-implanted GaN

KAUST Repository

O'Donnell, Kevin Peter; Roqan, Iman S.; Wang, Ke; Lorenz, Katharina; Alves, Eduardo Jorge; Boćkowski, Michał X.

2011-01-01

Several distinct luminescent centres form in GaN samples doped with Eu. One centre, Eu2, recently identified as the isolated, substitutional Eu impurity, EuGa, is dominant in ion-implanted samples annealed under very high pressures (1 GPa) of N2. According to structural determinations, such samples exhibit an essentially complete removal of lattice damage caused by the implantation process. A second centre, Eu1, probably comprising EuGa in association with an intrinsic lattice defect, produces a more complex emission spectrum. In addition there are several unidentified features in the 5D0 to 7F2 spectral region near 620 nm. We can readily distinguish Eu1 and Eu2 by their excitation spectra, in particular through their different sensitivities to above-gap and below-gap excitation. The present study extends recent work on photoluminescence/ excitation (PL/E) spectroscopy of Eu1 and Eu2 to arrive at an understanding of these mechanisms in terms of residual optically active defect concentrations. We also report further on the 'host-independent' excitation mechanism that is active in the case of a prominent minority centre. The relevance of this work to the operation of the red GaN:Eu light-emitting diode is discussed. © 2010 Elsevier B.V. All rights reserved.

Bound state and localization of excitation in many-body open systems

Science.gov (United States)

Cui, H. T.; Shen, H. Z.; Hou, S. C.; Yi, X. X.

2018-04-01

We study the exact bound state and time evolution for single excitations in one-dimensional X X Z spin chains within a non-Markovian reservoir. For the bound state, a common feature is the localization of single excitations, which means the spontaneous emission of excitations into the reservoir is prohibited. Exceptionally, the pseudo-bound state can be found, for which the single excitation has a finite probability of emission into the reservoir. In addition, a critical energy scale for bound states is also identified, below which only one bound state exists, and it is also the pseudo-bound state. The effect of quasirandom disorder in the spin chain is also discussed; such disorder induces the single excitation to locate at some spin sites. Furthermore, to display the effect of bound state and disorder on the preservation of quantum information, the time evolution of single excitations in spin chains is studied exactly. An interesting observation is that the excitation can stay at its initial location with high probability only when the bound state and disorder coexist. In contrast, when either one of them is absent, the information of the initial state can be erased completely or becomes mixed. This finding shows that the combination of bound state and disorder can provide an ideal mechanism for quantum memory.

Nanoantennas for surface enhanced infrared spectroscopy: Effects of interaction and higher order resonant excitations

Directory of Open Access Journals (Sweden)

J. Aizpurua

2011-09-01

Full Text Available The sensitivity in surface enhanced infrared spectroscopy (SEIRS strongly depends on where the resonant excitation is spectrally located compared to the molecular vibration that is to be enhanced. In this contribution, we study the effect of coupling in the electromagnetic properties of 2D gold nanorod arrays in the IR. We also study the SEIRS activity of higher order resonant excitations in long nanoantennas to identify polaritonic signals of a supporting SiO2 layer with nanometer thickness (3 nm on a silicon substrate.

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...

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.

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.)

Crystal and solution spectroscopy of einsteinium

International Nuclear Information System (INIS)

Carnall, W.T.

1978-01-01

Work on spectra and electronic structure of Es 3+ is reviewed. Laser-excited fluorescence spectroscopy was used to study Es 3+ -doped LaCl 3 crystals; fluorescence transitions and lifetimes were determined. A complete ground-state splitting diagram was also constructed for Es 3+ : LaCl 3 . Some data on excited states of Fm 3+ are also included. 12 figures

More about orbitally excited hadrons from lattice QCD

International Nuclear Information System (INIS)

DeGrand, T.A.; Hecht, M.W.

1992-01-01

This is the second of two papers describing the calculation of spectroscopy for orbitally excited states from lattice simulations of quantum chromodynamics. New features include higher statistics for P-wave systems and first results for the spectroscopy of D-wave mesons and baryons, for relatively heavy-quark masses. We parametrize the Coulomb gauge wave functions for P- and D-wave systems and compare them to those of their corresponding S-wave states

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.

Two-dimensional electronic femtosecond stimulated Raman spectroscopy

Directory of Open Access Journals (Sweden)

Ogilvie J.P.

2013-03-01

Full Text Available We report two-dimensional electronic spectroscopy with a femtosecond stimulated Raman scattering probe. The method reveals correlations between excitation energy and excited state vibrational structure following photoexcitation. We demonstrate the method in rhodamine 6G.

Kinetic studies following state-selective laser excitation: Annual performance report for the period March 15, 1987-March 14, 1988

International Nuclear Information System (INIS)

Keto, J.W.

1987-11-01

The objective of this contract is the study of state-to-state, electronic energy transfer reactions following two-photon laser excitation. We have specifically been studying reactions of Xe 5p 5 6p 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 in experiments in the coming months 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. 4 figs

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.

Spectroscopy of hadron resonances on the lattice

Energy Technology Data Exchange (ETDEWEB)

Bali, Gunnar; Burch, Tommy; Ehmann, Christian; Goeckeler, Meinulf; Hagen, Christian; Schaefer, Andreas [Institut fuer Theoretische Physik, Universitaet Regensburg, D-93040 Regensburg (Germany); Gattringer, Christof; Lang, Christian; Limmer, Markus; Mohler, Daniel [Institut fuer Physik, FB Theoretische Physik, Universitaet Graz, A-8010 Graz (Austria)

2009-07-01

The reproduction of the hadron mass spectrum from first principles is an important task for lattice QCD. While ground state spectroscopy, especially in the quenched approximation, is by now well understood, a clean extraction of excited hadron masses from a lattice QCD simulation still is a serious challenge. We discuss the relevant techniques for spectroscopy calculations on the lattice, in particular the variational technique which is needed for separating the different excited states from the ground state. Using this method we study three different sectors of the hadron spectrum. In the light quark sector we present hadron masses obtained from simulations with dynamical approximately chiral fermions, so-called Chirally Improved Fermions. For charmonium, we are able to extract masses for a number of excited states including ones with higher spin and exotic quantum numbers. The heavy-light hadron sector is investigated in the static-light approximation, i.e., the heavy quark is treated as infinitely heavy. Also here we are able to determine a large number of excitations.

On excited states in real-time AdS/CFT

Energy Technology Data Exchange (ETDEWEB)

Botta-Cantcheff, Marcelo; Martínez, Pedro J.; Silva, Guillermo A. [Instituto de Física de La Plata - CONICET & Departamento de Física - UNLP,C.C. 67, 1900 La Plata (Argentina)

2016-02-25

The Skenderis-van Rees prescription, which allows the calculation of time-ordered correlation functions of local operators in CFT’s using holographic methods is studied and applied for excited states. Calculation of correlators and matrix elements of local CFT operators between generic in/out states are carried out in global Lorentzian AdS. We find the precise form of such states, obtain an holographic formula to compute the inner product between them, and using the consistency with other known prescriptions, we argue that the in/out excited states built according to the Skenderis-Van Rees prescription correspond to coherent states in the (large-N) AdS-Hilbert space. This is confirmed by explicit holographic computations. The outcome of this study has remarkable implications on generalizing the Hartle-Hawking construction for wave functionals of excited states in AdS quantum gravity.

Investigation of excited states populations density of Hall thruster plasma in three dimensions by laser-induced fluorescence spectroscopy

Science.gov (United States)

Krivoruchko, D. D.; Skrylev, A. V.

2018-01-01

The article deals with investigation of the excited states populations distribution of a low-temperature xenon plasma in the thruster with closed electron drift at 300 W operating conditions were investigated by laser-induced fluorescence (LIF) over the 350-1100 nm range. Seven xenon ions (Xe II) transitions were analyzed, while for neutral atoms (Xe I) just three transitions were explored, since the majority of Xe I emission falls into the ultraviolet or infrared part of the spectrum and are difficult to measure. The necessary spontaneous emission probabilities (Einstein coefficients) were calculated. Measurements of the excited state distribution were made for points (volume of about 12 mm3) all over the plane perpendicular to thruster axis in four positions on it (5, 10, 50 and 100 mm). Measured LIF signal intensity have differences for each location of researched point (due to anisotropy of thruster plume), however the structure of states populations distribution persisted at plume and is violated at the thruster exit plane and cathode area. Measured distributions show that for describing plasma of Hall thruster one needs to use a multilevel kinetic model, classic model can be used just for far plume region or for specific electron transitions.

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.)

Laser pulses for coherent xuv Raman excitation

Science.gov (United States)

Greenman, Loren; Koch, Christiane P.; Whaley, K. Birgitta

2015-07-01

We combine multichannel electronic structure theory with quantum optimal control to derive femtosecond-time-scale Raman pulse sequences that coherently populate a valence excited state. For a neon atom, Raman target populations of up to 13% are obtained. Superpositions of the ground and valence Raman states with a controllable relative phase are found to be reachable with up to 4.5% population and arbitrary phase control facilitated by the pump pulse carrier-envelope phase. Analysis of the optimized pulse structure reveals a sequential mechanism in which the valence excitation is reached via a fast (femtosecond) population transfer through an intermediate resonance state in the continuum rather than avoiding intermediate-state population with simultaneous or counterintuitive (stimulated Raman adiabatic passage) pulse sequences. Our results open a route to coupling valence excitations and core-hole excitations in molecules and aggregates that locally address specific atoms and represent an initial step towards realization of multidimensional spectroscopy in the xuv and x-ray regimes.

Role of Solvent, pH, and Molecular Size in Excited-State Deactivation of Key Eumelanin Building Blocks: Implications for Melanin Pigment Photostability

DEFF Research Database (Denmark)

Gauden, M.; Pezzella, A.; Panzella, L.

2008-01-01

  Ultrafast time-resolved fluorescence spectroscopy has been used to investigate the excited state dynamics of the basic eumelanin building block 5,6-dihydroxyindole-2-carboxylic acid  (DHICA) its acetylated, methylated and carboxylic ester derivatives as well as two oligomers, a dimer and a trim...

Detailed Characterization of a Nanosecond-Lived Excited State: X-ray and Theoretical Investigation of the Quintet State in Photoexcited [Fe(terpy) 2 ] 2+

International Nuclear Information System (INIS)

Vanko, Gyorgy; Bordage, Amelie; Papai, Matyas; Haldrup, Kristoffer; March, Anne Marie; Galler, Andreas; Assefa, Tadesse; Cabaret, Delphine; Juhin, Amelie; Driel, Tim B. van; Gallo, Erik; Rovezzi, Mauro; Nemeth, Zoltan; Rozsalyi, Emese; Rozgonyi, Tamas; Uhlig, Jens; Gawelda, Wojciech

2015-01-01

Theoretical predictions show that depending on the populations of the Fe 3d xy , 3d xz , and 3d yz orbitals two possible quintet states can exist for the high-spin state of the photoswitchable model system [Fe(terpy) 2 ] 2+ . The differences in the structure and molecular properties of these 5B2 and 5E quintets are very small and pose a substantial challenge for experiments to resolve them. Yet for a better understanding of the physics of this system, which can lead to the design of novel molecules with enhanced photoswitching performance, it is vital to determine which high-spin state is reached in the transitions that follow the light excitation. The quintet state can be prepared with a short laser pulse and can be studied with cutting-edge time-resolved X-ray techniques. Here we report on the application of an extended set of X-ray spectroscopy and scattering techniques applied to investigate the quintet state of [Fe(terpy) 2 ] 2+ 80 ps after light excitation. High-quality X-ray absorption, nonresonant emission, and resonant emission spectra as well as X-ray diffuse scattering data clearly reflect the formation of the high-spin state of the [Fe(terpy) 2 ] 2+ molecule; moreover, extended X-ray absorption fine structure spectroscopy resolves the Fe-ligand bond-length variations with unprecedented bond-length accuracy in time-resolved experiments. With ab initio calculations we determine why, in contrast to most related systems, one configurational mode is insufficient for the description of the low-spin (LS)-high-spin (HS) transition. We identify the electronic structure origin of the differences between the two possible quintet modes, and finally, we unambiguously identify the formed quintet state as 5E, in agreement with our theoretical expectations

Shifted excitation Raman difference spectroscopy for authentication of cheese and cheese analogues

Science.gov (United States)

Sowoidnich, Kay; Kronfeldt, Heinz-Detlef

2016-04-01

Food authentication and the detection of adulterated products are recent major issues in the food industry as these topics are of global importance for quality control and food safety. To effectively address this challenge requires fast, reliable and non-destructive analytical techniques. Shifted Excitation Raman Difference Spectroscopy (SERDS) is well suited for identification purposes as it combines the chemically specific information obtained by Raman spectroscopy with the ability for efficient fluorescence rejection. The two slightly shifted excitation wavelengths necessary for SERDS are realized by specially designed microsystem diode lasers. At 671 nm the laser (optical power: 50 mW, spectral shift: 0.7 nm) is based on an external cavity configuration whereas an emission at 783 nm (optical power: 110 mW, spectral shift: 0.5 nm) is achieved by a distributed feedback laser. To investigate the feasibility of SERDS for rapid and nondestructive authentication purposes four types of cheese and three different cheese analogues were selected. Each sample was probed at 8 different positions using integration times of 3-10 seconds and 10 spectra were recorded at each spot. Principal components analysis was applied to the SERDS spectra revealing variations in fat and protein signals as primary distinction criterion between cheese and cheese analogues for both excitation wavelengths. Furthermore, to some extent, minor compositional differences could be identified to discriminate between individual species of cheese and cheese analogues. These findings highlight the potential of SERDS for rapid food authentication potentially paving the way for future applications of portable SERDS systems for non-invasive in situ analysis.

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

Low energy nuclear spin excitations in Ho metal investigated by high resolution neutron spectroscopy.

Science.gov (United States)

Chatterji, Tapan; Jalarvo, Niina

2013-04-17

We have investigated the low energy excitations in metallic Ho by high resolution neutron spectroscopy. We found at T = 3 K clear inelastic peaks in the energy loss and energy gain sides, along with the central elastic peak. The energy of this low energy excitation, which is 26.59 ± 0.02 μeV at T = 3 K, decreased continuously and became zero at TN ≈ 130 K. By fitting the data in the temperature range 100-127.5 K with a power law we obtained the power-law exponent β = 0.37 ± 0.02, which agrees with the expected value β = 0.367 for a three-dimensional Heisenberg model. Thus the energy of the low energy excitations can be associated with the order parameter.

Comparison endpoint study of process plasma and secondary electron beam exciter optical emission spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Stephan Thamban, P. L.; Yun, Stuart; Padron-Wells, Gabriel; Hosch, Jimmy W.; Goeckner, Matthew J. [Department of Mechanical Engineering, University of Texas at Dallas, 800W Campbell Road, Richardson, Texas 75080 (United States); Department of Electrical Engineering, University of Texas at Dallas, 800W Campbell Road, Richardson, Texas 75080 (United States); Verity Instruments, Inc., 2901 Eisenhower Street, Carrollton, Texas 75007 (United States); Department of Mathematical Sciences, University of Texas at Dallas, 800 W Campbell Road, Richardson, Texas 75080 (United States)

2012-11-15

Traditionally process plasmas are often studied and monitored by optical emission spectroscopy. Here, the authors compare experimental measurements from a secondary electron beam excitation and direct process plasma excitation to discuss and illustrate its distinctiveness in the study of process plasmas. They present results that show excitations of etch process effluents in a SF{sub 6} discharge and endpoint detection capabilities in dark plasma process conditions. In SF{sub 6} discharges, a band around 300 nm, not visible in process emission, is observed and it can serve as a good indicator of etch product emission during polysilicon etches. Based on prior work reported in literature the authors believe this band is due to SiF{sub 4} gas phase species.

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.

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.

Ultrafast Excited-State Dynamics of Diketopyrrolopyrrole (DPP)-Based Materials: Static versus Diffusion-Controlled Electron Transfer Process

KAUST Repository

Alsulami, Qana

2015-06-25

Singlet-to-triplet intersystem crossing (ISC) and photoinduced electron transfer (PET) of platinum(II) containing diketopyrrolopyrrole (DPP) oligomer in the absence and presence of strong electron-acceptor tetracyanoethylene (TCNE) were investigated using femtosecond and nanosecond transient absorption spectroscopy with broadband capabilities. The role of platinum(II) incorporation in those photophysical properties was evaluated by comparing the excited-state dynamics of DPP with and without the metal centers. The steady-state measurements reveal that platinum(II) incorporation facilitates dramatically the interactions between DPP-Pt(acac) and TCNE, resulting in charge transfer (CT) complex formation. The transient absorption spectra in the absence of TCNE reveal ultrafast ISC of DPP-Pt(acac) followed by their long-lived triplet state. In the presence of TCNE, PET from the excited DPP-Pt(acac) and DPP to TCNE, forming the radical ion pairs. The ultrafast PET which occurs statically from DPP-Pt(acac) to TCNE in picosecond regime, is much faster than that from DPP to TCNE (nanosecond time scale) which is diffusion-controlled process, providing clear evidence that PET rate is eventually controlled by the platinum(II) incorporation.

Ultrafast Excited-State Dynamics of Diketopyrrolopyrrole (DPP)-Based Materials: Static versus Diffusion-Controlled Electron Transfer Process

KAUST Repository

Alsulami, Qana; Aly, Shawkat Mohammede; Goswami, Subhadip; Alarousu, Erkki; Usman, Anwar; Schanze, Kirk S.; Mohammed, Omar F.

2015-01-01

Singlet-to-triplet intersystem crossing (ISC) and photoinduced electron transfer (PET) of platinum(II) containing diketopyrrolopyrrole (DPP) oligomer in the absence and presence of strong electron-acceptor tetracyanoethylene (TCNE) were investigated using femtosecond and nanosecond transient absorption spectroscopy with broadband capabilities. The role of platinum(II) incorporation in those photophysical properties was evaluated by comparing the excited-state dynamics of DPP with and without the metal centers. The steady-state measurements reveal that platinum(II) incorporation facilitates dramatically the interactions between DPP-Pt(acac) and TCNE, resulting in charge transfer (CT) complex formation. The transient absorption spectra in the absence of TCNE reveal ultrafast ISC of DPP-Pt(acac) followed by their long-lived triplet state. In the presence of TCNE, PET from the excited DPP-Pt(acac) and DPP to TCNE, forming the radical ion pairs. The ultrafast PET which occurs statically from DPP-Pt(acac) to TCNE in picosecond regime, is much faster than that from DPP to TCNE (nanosecond time scale) which is diffusion-controlled process, providing clear evidence that PET rate is eventually controlled by the platinum(II) incorporation.

Auger electron spectroscopy, ionization loss spectroscopy, appearance potential spectroscopy

International Nuclear Information System (INIS)

Riwan, R.

1973-01-01

The spectroscopy of surfaces using an incident electron beam is studied. The fundamental mechanisms are discussed together with the parameters involved in Auger emission: excitation of the atom, de-excitation by electron emission, and the migration of electrons towards the surface and their ejection. Some examples of applications are given (surface structures, metallurgy, chemical information). Two new techniques for analyzing surfaces are studied: ionization spectroscopy, and appearance potential spectroscopy [fr

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.

Emission Spectroscopy as a Probe into Photoinduced Intramolecular Electron Transfer in Polyazine Bridged Ru(II,Rh(III Supramolecular Complexes

Directory of Open Access Journals (Sweden)

Karen J. Brewer

2010-08-01

Full Text Available Steady-state and time-resolved emission spectroscopy are valuable tools to probe photochemical processes of metal-ligand, coordination complexes. Ru(II polyazine light absorbers are efficient light harvesters absorbing in the UV and visible with emissive 3MLCT excited states known to undergo excited state energy and electron transfer. Changes in emission intensity, energy or band-shape, as well as excited state lifetime, provide insight into excited state dynamics. Photophysical processes such as intramolecular electron transfer between electron donor and electron acceptor sub-units may be investigated using these methods. This review investigates the use of steady-state and time-resolved emission spectroscopy to measure excited state intramolecular electron transfer in polyazine bridged Ru(II,Rh(III supramolecular complexes. Intramolecular electron transfer in these systems provides for conversion of the emissive 3MLCT (metal-to-ligand charge transfer excited state to a non-emissive, but potentially photoreactive, 3MMCT (metal-to-metal charge transfer excited state. The details of the photophysics of Ru(II,Rh(III and Ru(II,Rh(III,Ru(II systems as probed by steady-state and time-resolved emission spectroscopy will be highlighted.

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

Participation of electronic excited states in the positronium formation mechanism in the Gd(III) pentakis (picrate) complexes with imidazolium countercations

Energy Technology Data Exchange (ETDEWEB)

Fulgêncio, F., E-mail: fefulgencio@gmail.com [Departam ento de Química – ICEx Universidade Federal de Minas Gerais – UFMG, Belo Horizonte, MG (Brazil); Borges, A.S. [Coordenadoria de Química e Biologia – Instituto Federal do Espírito Santos – IFES, Campus Vitória, ES (Brazil); Araújo, M.H. [Departam ento de Química – ICEx Universidade Federal de Minas Gerais – UFMG, Belo Horizonte, MG (Brazil); Brito, H.F. [Instituto de Química, Departamento de Química Fundamental, Universidade de São Paulo, São Paulo (Brazil); Oliveira, F.C. [Departamento de Metalurgia e Química, Centro Federal de Educação Tecnológica de Minas Gerais – CEFET-MG, Campus Timóteo, MG (Brazil); Ribeiro, T.; Windmöller, D. [Departam ento de Química – ICEx Universidade Federal de Minas Gerais – UFMG, Belo Horizonte, MG (Brazil); Magalhães, W.F., E-mail: welmag@ufmg.br [Departam ento de Química – ICEx Universidade Federal de Minas Gerais – UFMG, Belo Horizonte, MG (Brazil)

2016-02-15

In this work, positron annihilation lifetime (PALS) and optical spectroscopies measurements were performed on [Gd(pic){sub 2}(H{sub 2}O){sub 6}](pic)·6H{sub 2}O and on complexes of general formula C{sub 2}[Gd(pic){sub 5}], where pic corresponds to picrate ligands and C to the countercations butyl-methyl, hexyl-methyl, butyl-ethyl and butyl-butyl imidazoles. Since all of these complexes have high energy ligand-to-metal charge transfer states (LMCTS) but form low amounts of Positronium (Ps), the LMCTS do not act here as a mechanism that suppress luminescence nor prevents Ps formation. This result suggests that, besides LMCTS, other effects should also contribute to prevent Ps formation. The results indicate that the electron withdrawing –NO{sub 2} groups in the picrate ligand are responsible by the effect that prevents Ps formation. Also, a rough correlation between the ligands' triplet states lifetimes and Ps formation was observed. The insertion of electron donor groups (the imidazolium countercations) increased the ligands' first triplet excited states ({sup 3}π{sup ⁎}) lifetimes and Ps formation, indicating that these two spectroscopic parameters are correlated. Also, it is demonstrated that there is no clear correlation between Ps formation probability and the excitation energy of the ligands' first triplet excited states. The results were discussed in terms of the recently proposed Ps formation mechanism, named cybotactic correlated system kinetic mechanism (CCSKM), showing that the Ps formation process involves molecular excited states and is kinetically controlled. - Highlights: • PALS and optical spectroscopies measurements performed on Gd{sup 3+} complexes. • A correlation was obtained between the ligands' {sup 3}π{sup ⁎} lifetimes and Ps formation. • Electronegative groups increased the ligands' {sup 3}π{sup ⁎} lifetimes and Ps formation. • Results discussed in terms of a new Ps formation mechanism (ccskm).

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.

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.

Excited State Charge Transfer reaction with dual emission from 5-(4-dimethylamino-phenyl)-penta-2,4-dienenitrile: Spectral measurement and theoretical density functional theory calculation

Science.gov (United States)

Jana, Sankar; Dalapati, Sasanka; Ghosh, Shalini; Kar, Samiran; Guchhait, Nikhil

2011-07-01

The excited state intramolecular charge transfer process in donor-chromophore-acceptor system 5-(4-dimethylamino-phenyl)-penta-2,4-dienenitrile (DMAPPDN) has been investigated by steady state absorption and emission spectroscopy in combination with Density Functional Theory (DFT) calculations. This flexible donor acceptor molecule DMAPPDN shows dual fluorescence corresponding to emission from locally excited and charge transfer state in polar solvent. Large solvatochromic emission shift, effect of variation of pH and HOMO-LUMO molecular orbital pictures support excited state intramolecular charge transfer process. The experimental findings have been correlated with the calculated structure and potential energy surfaces based on the Twisted Intramolecular Charge Transfer (TICT) model obtained at DFT level using B3LYP functional and 6-31+G( d, p) basis set. The theoretical potential energy surfaces for the excited states have been generated in vacuo and acetonitrile solvent using Time Dependent Density Functional Theory (TDDFT) and Time Dependent Density Functional Theory Polarized Continuum Model (TDDFT-PCM) method, respectively. All the theoretical results show well agreement with the experimental observations.

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.

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

Baryon excitations in the bag model

International Nuclear Information System (INIS)

Jaffe, R.L.

1976-07-01

Two recent spectroscopic applications of the bag model are discussed. The first is a study of the place of multiquark states in meson and baryon spectroscopy, and the second is an attempt to sort out the P-wave baryon excitations in a bag model. 33 references

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.

Time-resolved spectroscopy defines perturbation in molecules

International Nuclear Information System (INIS)

Ahmed, K.

1998-01-01

Time-resolved LIF spectroscopy is employed in order to investigate perturbations in different excited electronic state of alkali molecules. Dunham Coefficients are used to search the selected excited ro-vibrational level, which is overlap with the other nearby excited states. Lifetime measurement has been performed of more than 50 ro-vibrational levels. Out of these 25 levels were observed drastically different lifetimes from the other unperturbed levels. In this report, influence of different perturbations on this anomalous behavior is investigated and discussed. (author)

A study of relaxation mechanisms in the A{sup 2}{Sigma}{sup +} state of nitric oxide by time resolved double resonant polarization spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Stampanoni-Panariello, A; Bombach, R; Hemmerling, B; Hubschmid, W [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-06-01

Double resonant polarization labeling spectroscopy is applied to detect nitric oxide in flames and to characterize rotational energy transfer and orientation changing collisions in its first excited electronic state. (author) 4 figs., 3 refs.

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)

First excited states in doubly-odd 110Sb: Smooth band termination in the A ∼ 110 region

International Nuclear Information System (INIS)

Lane, G.J.; Fossan, D.B.; Thorslund, I.

1996-01-01

Excited states have been identified for the first time in 110 Sb in a comprehensive series of γ-spectroscopy experiments, including recoil-mass and neutron-field measurements. Three high-spin decoupled bands with configurations based on 2p-2h excitations across the Z = 50 shell gap, are observed to show the features of smooth band termination, the first such observation in an odd-odd nucleus. The yrast intruder band has been connected to the low spin levels and is tentatively identified up to its predicred termination at I π = (45 + ). Detailed configuration assignments are made through comparison with configuration-dependent cranked Nilsson-Strutinsky calculations; excellent agreement with experiment is obtained. The systematic occurrence of smoothly terminating bands in the neighboring isotopes is discussed

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

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

Coulomb excitation of neutron-rich odd-$A$ Cd isotopes

CERN Multimedia

Reiter, P; Kruecken, R; Gernhaeuser, R A; Kroell, T; Leske, J; Marginean, N M

We propose to study excited states in the odd-${A}$ isotopes $^{123,125,127}$Cd by ${\\gamma}$-ray spectroscopy following "safe" Coulomb excitation. The experiment aims to determine the B(E2) values connecting excited states with the ground state as well as the long-lived (11/2$^{-}$) isomer. The proposed study profits from the unique capability of ISOLDE to produce beams containing Cd in the ground state or in the isomeric state. Our recent results on the neutron-rich even-A Cd nuclei appear to show that these nuclei may possess some collectivity beyond that calculated by modern shell-model predictions. Beyond-mean-field calculations also predict these nuclei to be weakly deformed. These facets are surprising considering their proximity to the doubly magic $^{132}$Sn. Coulomb-excitation studies of odd-${A}$ Cd isotopes may give a unique insight into the deformation-driving roles played by different orbits in this region. Such studies of the onset of collectivity become especially important in light of recent...

Temperature dependence of the hydrated electron's excited-state relaxation. I. Simulation predictions of resonance Raman and pump-probe transient absorption spectra of cavity and non-cavity models

Science.gov (United States)

Zho, Chen-Chen; Farr, Erik P.; Glover, William J.; Schwartz, Benjamin J.

2017-08-01

We use one-electron non-adiabatic mixed quantum/classical simulations to explore the temperature dependence of both the ground-state structure and the excited-state relaxation dynamics of the hydrated electron. We compare the results for both the traditional cavity picture and a more recent non-cavity model of the hydrated electron and make definite predictions for distinguishing between the different possible structural models in future experiments. We find that the traditional cavity model shows no temperature-dependent change in structure at constant density, leading to a predicted resonance Raman spectrum that is essentially temperature-independent. In contrast, the non-cavity model predicts a blue-shift in the hydrated electron's resonance Raman O-H stretch with increasing temperature. The lack of a temperature-dependent ground-state structural change of the cavity model also leads to a prediction of little change with temperature of both the excited-state lifetime and hot ground-state cooling time of the hydrated electron following photoexcitation. This is in sharp contrast to the predictions of the non-cavity model, where both the excited-state lifetime and hot ground-state cooling time are expected to decrease significantly with increasing temperature. These simulation-based predictions should be directly testable by the results of future time-resolved photoelectron spectroscopy experiments. Finally, the temperature-dependent differences in predicted excited-state lifetime and hot ground-state cooling time of the two models also lead to different predicted pump-probe transient absorption spectroscopy of the hydrated electron as a function of temperature. We perform such experiments and describe them in Paper II [E. P. Farr et al., J. Chem. Phys. 147, 074504 (2017)], and find changes in the excited-state lifetime and hot ground-state cooling time with temperature that match well with the predictions of the non-cavity model. In particular, the experiments

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.

Impact of nuclear lattice relaxation on the excitation energy transfer along a chain of pi-conjugated molecules

NARCIS (Netherlands)

Schmid, S.A.; Abbel, R.J.; Schenning, A.P.H.J.; Meijer, E.W.; Herz, L.M.

2010-01-01

We have investigated the extent to which delocalization of the ground-state and excited-state wave functions of a p-conjugated molecule affects the excitation energy transfer (EET) between such molecules. Using femtosecond photoluminescence spectroscopy, we experimentally monitored the EET along

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

Inner-shell excitation and ionic fragmentation of molecules

International Nuclear Information System (INIS)

Hitchcock, A.P.; Tyliszczak, T.; Cavell, R.G.

1997-01-01

Inner-shell excitation and associated decay spectroscopies are site specific probes of electronic and geometrical structure and photoionization dynamics. X-ray absorption probes the geometric and electronic structure, while time-of-flight mass spectrometry with multi-coincidence detection provides information on the photofragmentation dynamics of the initially produced inner-shell state. Auger decay of inner-shell excited and ionised states is an efficient source of multiply charged ions. The charge separation and fragmentation of these species, studied by photoelectron-photoion-photoion coincidence (also called charge separation mass spectrometry) gives insights into bonding and electronic structure. In molecules, the dependence of the fragmentation process on the X-ray energy can reveal cases of site and/or state selective fragmentation. At the ALS the authors have examined the soft X-ray spectroscopy and ionic fragmentation of a number of molecules, including carboranes, silylenes, phosphorus halides, SF 6 and CO 2 . Their work is illustrated using results from the carborane and PF 3 studies

Inner-shell excitation and ionic fragmentation of molecules

Energy Technology Data Exchange (ETDEWEB)

Hitchcock, A.P.; Tyliszczak, T. [McMaster Univ., Hamilton, Ontario (Canada); Cavell, R.G. [Univ. of Alberta, Edmonton (Canada)] [and others

1997-04-01

Inner-shell excitation and associated decay spectroscopies are site specific probes of electronic and geometrical structure and photoionization dynamics. X-ray absorption probes the geometric and electronic structure, while time-of-flight mass spectrometry with multi-coincidence detection provides information on the photofragmentation dynamics of the initially produced inner-shell state. Auger decay of inner-shell excited and ionised states is an efficient source of multiply charged ions. The charge separation and fragmentation of these species, studied by photoelectron-photoion-photoion coincidence (also called charge separation mass spectrometry) gives insights into bonding and electronic structure. In molecules, the dependence of the fragmentation process on the X-ray energy can reveal cases of site and/or state selective fragmentation. At the ALS the authors have examined the soft X-ray spectroscopy and ionic fragmentation of a number of molecules, including carboranes, silylenes, phosphorus halides, SF{sub 6} and CO{sub 2}. Their work is illustrated using results from the carborane and PF{sub 3} studies.

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....

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

Hard X-ray photoemission spectroscopy

International Nuclear Information System (INIS)

Kobayashi, Keisuke

2009-01-01

Except in the very early stage of the development of X-ray photoemission spectroscopy (XPS) by Kai Siegbahn and his coworkers, the excitation sources for XPS studies have predominantly been the Al Kα and Mg Kα emission lines. The advent of synchrotron radiation sources opened up the possibility of tuning the excitation photon energy with much higher throughputs for photoemission spectroscopy, however the excitation energy range was limited to the vacuum ultra violet and soft X-ray regions. Over the past 5-6 years, bulk-sensitive hard X-ray photoemission spectroscopy using high-brilliance high-flux X-rays from third generation synchrotron radiation facilities has been developed. This article reviews the history of HXPES covering the period from Kai Siegbahn and his coworkers' pioneering works to the present, and describes the fundamental aspects, instrumentation, applications to solid state physics, applied physics, materials science, and industrial applications of HXPES. Finally, several challenging new developments which have been conducted at SPring-8 by collaborations among several groups are introduced.

Femtosecond pump–probe spectroscopy of graphene oxide in water

International Nuclear Information System (INIS)

Shang, Jingzhi; Ma, Lin; Li, Jiewei; Ai, Wei; Yu, Ting; Gurzadyan, Gagik G

2014-01-01

Transient absorption properties of aqueous graphene oxide (GO) have been studied by use of femtosecond pump–probe spectroscopy. Excited state absorption and photobleaching are observed in the wide spectral range. The observed fast three lifetime components are attributed to the absorption of upper excited states and localized states, which is confirmed by both laser induced absorption and transmission kinetics. The longest time component is assigned to the lowest excited state of GO, which mainly originates from the sp2 domains. With the increase of the excitation power, two-quantum absorption occurs, which results in an additional rise-time component of the observed transients. (paper)

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.

Sub-Doppler spectroscopy of thioformaldehyde: Excited state perturbations and evidence for rotation-induced vibrational mixing in the ground state

International Nuclear Information System (INIS)

Clouthier, D.J.; Huang, G.; Adam, A.G.; Merer, A.J.

1994-01-01

High-resolution intracavity dye laser spectroscopy has been used to obtain sub-Doppler spectra of transitions to 350 rotational levels in the 4 1 0 band of the A 1 A 2 --X 1 A 1 electronic transition of thioformaldehyde. Ground state combination differences from the sub-Doppler spectra, combined with microwave and infrared data, have been used to improve the ground state rotational and centrifugal distortion constants of H 2 CS. The upper state shows a remarkable number of perturbations. The largest of these are caused by nearby triplet levels, with matrix elements of 0.05--0.15 cm -1 . A particularly clear singlet--triplet avoided crossing in K a ' = 7 has been shown to be caused by interaction with the F 1 component of the 3 1 6 2 vibrational level of the a 3 A 2 state. At least 53% of the S 1 levels show evidence of very small perturbations by high rovibronic levels of the ground state. The number of such perturbations is small at low J, but increases rapidly beyond J=5 such that 40%--80% of the observed S 1 levels of any given J are perturbed by ground state levels. Model calculations show that the density and J dependence of the number of perturbed levels can be explained if there is extensive rotation-induced mixing of the vibrational levels in the ground state

Electronic excited states and relaxation dynamics in polymer heterojunction systems

Science.gov (United States)

Ramon, John Glenn Santos

The potential for using conducting polymers as the active material in optoelectronic devices has come to fruition in the past few years. Understanding the fundamental photophysics behind their operations points to the significant role played by the polymer interface in their performance. Current device architectures involve the use of bulk heterojunctions which intimately blend the donor and acceptor polymers to significantly increase not only their interfacial surface area but also the probability of exciton formation within the vicinity of the interface. In this dissertation, we detail the role played by the interface on the behavior and performance of bulk heterojunction systems. First, we explore the relation between the exciton binding energy to the band offset in determining device characteristics. As a general rule, when the exciton binding energy is greater than the band offset, the exciton remains the lowest energy excited state leading to efficient light-emitting properties. On the other hand, if the offset is greater than the binding energy, charge separation becomes favorable leading to better photovoltaic behavior. Here, we use a Wannier function, configuration interaction based approach to examine the essential excited states and predict the vibronic absorption and emission spectra of the PPV/BBL, TFB/F8BT and PFB/F8BT heterojunctions. Our results underscore the role of vibrational relaxation in the formation of charge-transfer states following photoexcitation. In addition, we look at the relaxation dynamics that occur upon photoexcitation. For this, we adopt the Marcus-Hush semiclassical method to account for lattice reorganization in the calculation of the interconversion rates in TFB/F8BT and PFB/F8BT. We find that, while a tightly bound charge-transfer state (exciplex) remains the lowest excited state, a regeneration pathway to the optically active lowest excitonic state in TFB/F8BT is possible via thermal repopulation from the exciplex. Finally

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 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.

Excited state non-adiabatic dynamics of the smallest polyene, trans 1,3-butadiene. II. Ab initio multiple spawning simulations

Science.gov (United States)

Glover, William J.; Mori, Toshifumi; Schuurman, Michael S.; Boguslavskiy, Andrey E.; Schalk, Oliver; Stolow, Albert; Martínez, Todd J.

2018-04-01

The excited state non-adiabatic dynamics of the smallest polyene, trans 1,3-butadiene (BD), has long been the subject of controversy due to its strong coupling, ultrafast time scales and the difficulties that theory faces in describing the relevant electronic states in a balanced fashion. Here we apply Ab Initio Multiple Spawning (AIMS) using state-averaged complete active space multistate second order perturbation theory [SA-3-CAS(4/4)-MSPT2] which describes both static and dynamic electron correlation effects, providing a balanced description of both the initially prepared bright 11Bu (ππ*) state and non-adiabatically coupled dark 21Ag state of BD. Importantly, AIMS allows for on-the-fly calculations of experimental observables. We validate our approach by directly simulating the time resolved photoelectron-photoion coincidence spectroscopy results presented in Paper I [A. E. Boguslavskiy et al., J. Chem. Phys. 148, 164302 (2018)], demonstrating excellent agreement with experiment. Our simulations reveal that the initial excitation to the 11Bu state rapidly evolves via wavepacket dynamics that follow both bright- and dark-state pathways as well as mixtures of these. In order to test the sensitivity of the AIMS results to the relative ordering of states, we considered two hypothetical scenarios biased toward either the bright 1Bu or the dark 21Ag state. In contrast with AIMS/SA-3-CAS(4/4)-MSPT2 simulations, neither of these scenarios yields favorable agreement with experiment. Thus, we conclude that the excited state non-adiabatic dynamics in BD involves both of these ultrafast pathways.

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

Quantum entanglement of localized excited states at finite temperature

Energy Technology Data Exchange (ETDEWEB)

Caputa, Paweł [Yukawa Institute for Theoretical Physics (YITP), Kyoto University,Kyoto 606-8502 (Japan); Nordita, KTH Royal Institute of Technology and Stockholm University,Roslagstullsbacken 23, SE-106 91 Stockholm (Sweden); Simón, Joan; Štikonas, Andrius [School of Mathematics and Maxwell Institute for Mathematical Sciences,University of Edinburgh,King’s Buildings, Edinburgh EH9 3FD (United Kingdom); Takayanagi, Tadashi [Yukawa Institute for Theoretical Physics (YITP), Kyoto University,Kyoto 606-8502 (Japan); Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU),University of Tokyo,Kashiwa, Chiba 277-8582 (Japan)

2015-01-20

In this work we study the time evolutions of (Renyi) entanglement entropy of locally excited states in two dimensional conformal field theories (CFTs) at finite temperature. We consider excited states created by acting with local operators on thermal states and give both field theoretic and holographic calculations. In free field CFTs, we find that the growth of Renyi entanglement entropy at finite temperature is reduced compared to the zero temperature result by a small quantity proportional to the width of the localized excitations. On the other hand, in finite temperature CFTs with classical gravity duals, we find that the entanglement entropy approaches a characteristic value at late time. This behaviour does not occur at zero temperature. We also study the mutual information between the two CFTs in the thermofield double (TFD) formulation and give physical interpretations of our results.

High resolution spectroscopy in the second excited torsional state of $CH_{3}/OD$ and the atlas of the Fourier transform spectrum in the range 20-205 cm$^{-1}/$...

CERN Document Server

Mukhopadhyay, I

1999-01-01

In this work, the reduced eighth order Hamiltonian that has been used for the determination of the molecular parameters-using the high resolution Fourier transform far-infrared (FIR) assigned transitions in the ground and first $9 excited torsional states of CH/sub 3/OD-has been applied to assign and refine the model for the second excited torsional state. The data set consisted of 1220 FIR transitions with the rotational angular momentum J<21 and K<7 in the $9 second excited torsional state. It should be noted that the second excited torsional states of methanol are almost at the top of the torsional barrier. Thus it was interesting to see how the large amplitude motion is taken care of by $9 the eighth order Hamiltonian. We are in the process of a global fit including all the assigned transitions up to the second excited state. Additionally, in this paper we present the detailed Fourier transform spectral map of CH/sub $9 3/OD in the range 20-205 cm/sup -1/, as was done for the parent species. This sp...

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.

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.

Hybridized electronic states in potassium-doped picene probed by soft x-ray spectroscopies

Directory of Open Access Journals (Sweden)

Hiroyuki Yamane

2012-12-01

Full Text Available The electronic structure of the unoccupied and occupied states of potassium (K-doped and undoped picene crystalline films has been investigated by using the element-selective and bulk-sensitive photon-detection methods of X-ray absorption and emission spectroscopies. We observed the formation of the doping-induced unoccupied and occupied electronic states in K-doped picene. By applying the inner-shell resonant-excitation experiments, we observed the evidence for the orbital hybridization between K and picene near the Fermi energy. Furthermore, the resonant X-ray emission experiment suggests the presence of the Raman-active vibronic interaction in K-doped picene. These experimental evidences play a crucial role in the superconductivity of K-doped picene.

X-ray spectroscopy studies of nonradiative energy transfer processes in luminescent lanthanide materials

Science.gov (United States)

Pacold, Joseph I.

Luminescent materials play important roles in energy sciences, through solid state lighting and possible applications in solar energy utilization, and in biomedical research and applications, such as in immunoassays and fluorescence microscopy. The initial excitation of a luminescent material leads to a sequence of transitions between excited states, ideally ending with the emission of one or more optical-wavelength photons. It is essential to understand the microscopic physics of this excited state cascade in order to rationally design materials with high quantum efficiencies or with other fine-tuning of materials response. While optical-wavelength spectroscopies have unraveled many details of the energy transfer pathways in luminescent materials, significant questions remain open for many lanthanide-based luminescent materials. For organometallic dyes in particular, quantum yields remain limited in comparison with inorganic phosphors. This dissertation reports on a research program of synchrotron x-ray studies of the excited state electronic structure and energy-relaxation cascade in trivalent lanthanide phosphors and dyes. To this end, one of the primary results presented here is the first time-resolved x-ray absorption near edge spectroscopy studies of the transient 4f excited states in lanthanide-activated luminescent dyes and phosphors. This is a new application of time-resolved x-ray absorption spectroscopy that makes it possible to directly observe and, to some extent, quantify intramolecular nonradiative energy transfer processes. We find a transient increase in 4f spectral weight associated with an excited state confined to the 4f shell of trivalent Eu. This result implies that it is necessary to revise the current theoretical understanding of 4f excitation in trivalent lanthanide activators: either transient 4f-5d mixing effects are much stronger than previously considered, or else the lanthanide 4f excited state has an unexpectedly large contribution

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.)

LABORATORY CHARACTERIZATION AND ASTROPHYSICAL DETECTION OF VIBRATIONALLY EXCITED STATES OF ETHYL CYANIDE

Energy Technology Data Exchange (ETDEWEB)

Daly, A. M.; Bermudez, C.; Alonso, J. L. [Grupo de Espectroscopia Molecular (GEM), Edificio Quifima, Area de Quimica-Fisica, Laboratorios de Espectroscopia y Bioespectroscopia, Unidad Asociada del CSIC, Universidad de Valladolid, E-47005 Valladolid (Spain); Lopez, A.; Tercero, B.; Cernicharo, J. [Department of Astrophysics, CAB, INTA-CSIC, Crta Torrejon, E-28850 Torrejon de Ardoz, Madrid (Spain); Pearson, J. C. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Padadena, CA 91109 (United States); Marcelino, N., E-mail: adammichael.daly@uva.es, E-mail: cbermu@qf.uva.es, E-mail: jlalonso@qf.uva.es, E-mail: lopezja@cab.inta-csic.es, E-mail: terceromb@cab.inta-csic.es, E-mail: jcernicharo@cab.inta-csic.es, E-mail: John.C.Pearson@jpl.nasa.gov, E-mail: nmarceli@nrao.edu [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States)

2013-05-01

Ethyl cyanide, CH{sub 3}CH{sub 2}CN, is an important interstellar molecule with a very dense rotational-vibrational spectrum. On the basis of new laboratory data in the range of 17-605 GHz and ab initio calculations, two new vibrational states, {nu}{sub 12} and {nu}{sub 20}, have been detected in molecular clouds of Orion. Laboratory data consist of Stark spectroscopy (17-110 GHz) and frequency-modulated spectrometers (GEM laboratory in Valladolid: 17-170, 270-360 GHz; Toyama: 26-200 GHz; Emory: 200-240 GHz; Ohio State: 258-368 GHz; and JPL: 270-318, 395-605 GHz). More than 700 distinct lines of each species were measured in J up to 71 and in K{sub a} up to 25. The states were fitted with Watson's S-reduction Hamiltonian. The two new states have been identified in the interstellar medium toward the Orion Nebula (Orion KL). The ground state, the isotopologues of CH{sub 3}CH{sub 2}CN, and the vibrationally excited states have been fitted to obtain column densities and to derive vibrational temperatures. All together, ethyl cyanide is responsible for more than 2000 lines in the observed frequency range of 80-280 GHz.

Photoinduced dynamics of a cyanine dye: parallel pathways of non-radiative deactivation involving multiple excited-state twisted transients.

Science.gov (United States)

Upadhyayula, Srigokul; Nuñez, Vicente; Espinoza, Eli M; Larsen, Jillian M; Bao, Duoduo; Shi, Dewen; Mac, Jenny T; Anvari, Bahman; Vullev, Valentine I

2015-04-01

Cyanine dyes are broadly used for fluorescence imaging and other photonic applications. 3,3'-Diethylthiacyanine (THIA) is a cyanine dye composed of two identical aromatic heterocyclic moieties linked with a single methine, -CH 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 . The torsional degrees of freedom around the methine bonds provide routes for non-radiative decay, responsible for the inherently low fluorescence quantum yields. Using transient absorption spectroscopy, we determined that upon photoexcitation, the excited state relaxes along two parallel pathways producing three excited-state transients that undergo internal conversion to the ground state. The media viscosity impedes the molecular modes of ring rotation and preferentially affects one of the pathways of non-radiative decay, exerting a dominant effect on the emission

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.

X-ray-excited Auger and photoelectron spectroscopy

International Nuclear Information System (INIS)

Weightman, P.

1982-01-01

This article reviews developments in the understanding of x-ray-excited Auger and photoelectron spectra in the light of theoretical developments in atomic, molecular and solid-state physics. After reviewing progress in XPS and AES separately emphasis is placed on the inter-relationship between the two fields: Auger rates, for example, are the dominant contribution to core-level XPS linewidths and by combining XPS and AES it is possible to deduce information about Coster-Kronig processes which are difficult to study directly. An account is given of how the combination of measurements of environmentally dependent shifts in XPS and AES energies allows one to isolate initial- and final-state contributions which can then be related to the results of other experimental techniques. There is a brief discussion of many-electron effects and a discussion of how the combination of XPS and AES spectra involving valence levels enables the effects of hole-state localisation to be studied. (author)

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)

Laser excitation of SF6: spectroscopy and coherent pulse propagation effects

International Nuclear Information System (INIS)

Cantrell, C.D.; Makarov, A.A.; Louisell, W.H.

1978-01-01

Recent theoretical studies of coherent propagation effects in SF 6 and other polyatomic molecules are summarized beginning with an account of relevant aspects of the high-resolution spectroscopy of the ν 3 band of SF 6 . A laser pulse propagating in a molecular gas can acquire new frequencies which were not initially present in the pulse, and, in fact, a wave is coherently generated at the frequency of every molecular transition accessible from the initial molecular energy levels. The possible consequences of coherent generation of sidebands for the multiple-photon excitation of SF 6 and other polyatomic molecules are discussed

Evaluation of Shifted Excitation Raman Difference Spectroscopy and Comparison to Computational Background Correction Methods Applied to Biochemical Raman Spectra.

Science.gov (United States)

Cordero, Eliana; Korinth, Florian; Stiebing, Clara; Krafft, Christoph; Schie, Iwan W; Popp, Jürgen

2017-07-27

Raman spectroscopy provides label-free biochemical information from tissue samples without complicated sample preparation. The clinical capability of Raman spectroscopy has been demonstrated in a wide range of in vitro and in vivo applications. However, a challenge for in vivo applications is the simultaneous excitation of auto-fluorescence in the majority of tissues of interest, such as liver, bladder, brain, and others. Raman bands are then superimposed on a fluorescence background, which can be several orders of magnitude larger than the Raman signal. To eliminate the disturbing fluorescence background, several approaches are available. Among instrumentational methods shifted excitation Raman difference spectroscopy (SERDS) has been widely applied and studied. Similarly, computational techniques, for instance extended multiplicative scatter correction (EMSC), have also been employed to remove undesired background contributions. Here, we present a theoretical and experimental evaluation and comparison of fluorescence background removal approaches for Raman spectra based on SERDS and EMSC.

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.

Ultrafast electronic relaxation of excited state vitamin B12 in the gas phase

International Nuclear Information System (INIS)

Shafizadeh, Niloufar; Poisson, Lionel; Soep, Benoit

2008-01-01

The time evolution of electronically excited vitamin B 12 (cyanocobalamin) has been observed for the first time in the gas phase. It reveals an ultrafast decay to a state corresponding to metal excitation. This decay is interpreted as resulting from a ring to metal electron transfer. This opens the observation of the excited state of other complex biomimetic systems in the gas phase, the key to the characterisation of their complex evolution through excited electronic states

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.

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.

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.

Optical spectroscopy of orbital and magnetic excitations in vanadates and cuprates

International Nuclear Information System (INIS)

Benckiser, Eva Vera

2007-10-01

Within the scope of this thesis, the low-energy excitations of undoped Mott insulators RVO 3 with R = Y, Ho, and Ce, (Sr,Ca)CuO 2 and La 8 Cu 7 O 19 have been investigated by means of optical spectroscopy. The compounds RVO 3 with R=rare-earth ion recently have attracted a lot of interest because of their unusual structural, orbital, and magnetic properties. The compounds undergo a series of temperatureinduced phase transitions accompanied by a change of orbital and magnetic order. Furthermore, it has been proposed that YVO 3 represents the first realization of a one-dimensional orbital liquid and an orbital Peierls phase, with a transition to an orbitally ordered phase at lower temperatures. In this thesis, we present the optical conductivity σ(ω) of RVO 3 with R=Y, Ho, and Ce for energies from 0.1 to 1.6 eV as a function of temperature (10-300 K) and polarization of the incident light parallel to the crystallographic axes (σ a ,σ b ,σ c ). Our main experimental result is the observation of two absorption features at 0.55 eV in σ a (ω) and 0.4 eV in σ c (ω) which are assigned to collective orbital excitations, in contrast to conventional local crystal-field transitions. Altogether, our results strongly suggest that in RVO 3 with R=Y, Ho, and Ce the orbital exchange interactions play a decisive role. In a second study, we have investigated the magnetic excitations of low-dimensional quantum magnets, namely the spin chain (Sr,Ca)CuO 2 and the five-leg ladder La 8 Cu 7 O 19 . For (Sr,Ca)CuO 2 , two absorption features around 0.4 eV in σ c (ω) (chain direction) and σ b (ω) (inter-chain direction) are identified as magnetic contributions to the optical conductivity. The analysis of σ c (ω) enables the very precise determination of the nearest-neighbor exchange coupling J c as a function of temperature and Ca substitution. We have found J c =(227±4) meV for SrCuO 2 at low temperatures and no effect on J c upon Ca-substitution of 10%. Furthermore, we

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

Investigation of the spectroscopy and relaxation dynamics of benzaldehyde using molecular orbital calculations and laser ionization time-of-flight mass spectroscopy

Science.gov (United States)

da Silva, Maria Cristina Rodrigues

1998-11-01

Molecular orbital methods and laser ionization mass spectrometry measurements are used to investigate the spectroscopy and relaxation dynamics of benzaldehyde following excitation to its S2(/pi/pi/sp/*) state. Energies, equilibrium geometries and vibrational frequencies of ground and low-lying excited states of benzaldehyde neutral and cation determined by ab initio calculations provide a theoretical description of the electronic spectroscopy of benzaldehyde and of the changes occurring on excitation and ionization. The S2(/pi/pi/sp/*)[/gets]S0 excitation spectrum of jet-cooled benzaldehyde acquired using two-color laser ionization mass spectrometry techniques is interpreted with the aid of these calculations. The spectrum is dominated by the origin band and by transitions involving some of the ring modes consistent with the results of the molecular orbital calculations that indicate that the major geometric changes on excitation to S2 are located in the aromatic ring. Ten fundamental vibrations of the S2(/pi/pi/sp/*) state are assigned. The dissociation dynamics of benzaldehyde into benzene and carbon monoxide following excitation to its S2(/pi/pi/sp/*) state are investigated under jet- cooled conditions by two-color laser ionization mass spectrometry using a pump-probe technique. This experimental arrangement allows monitoring the benzaldehyde reactant and the benzene product ion signals as a function of the time delay between the excitation and ionization steps. A kinetic model is proposed to explain the observed biexponential decay of the benzaldehyde signal and the single exponential growth of the benzene product signal in terms of a sequential decay of two excited states of benzaldehyde, one of which leads to formation of benzene molecules in its lowest triplet state. Reactant disappearance and product appearance rates are determined for a number of vibronic transitions of the S2 state. They are found to increase with excitation energy without any indication

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.)

Excited state non-adiabatic dynamics of the smallest polyene, trans 1,3-butadiene. II. Ab initio multiple spawning simulations.

Science.gov (United States)

Glover, William J; Mori, Toshifumi; Schuurman, Michael S; Boguslavskiy, Andrey E; Schalk, Oliver; Stolow, Albert; Martínez, Todd J

2018-04-28

The excited state non-adiabatic dynamics of the smallest polyene, trans 1,3-butadiene (BD), has long been the subject of controversy due to its strong coupling, ultrafast time scales and the difficulties that theory faces in describing the relevant electronic states in a balanced fashion. Here we apply Ab Initio Multiple Spawning (AIMS) using state-averaged complete active space multistate second order perturbation theory [SA-3-CAS(4/4)-MSPT2] which describes both static and dynamic electron correlation effects, providing a balanced description of both the initially prepared bright 1 1 B u (ππ*) state and non-adiabatically coupled dark 2 1 A g state of BD. Importantly, AIMS allows for on-the-fly calculations of experimental observables. We validate our approach by directly simulating the time resolved photoelectron-photoion coincidence spectroscopy results presented in Paper I [A. E. Boguslavskiy et al., J. Chem. Phys. 148, 164302 (2018)], demonstrating excellent agreement with experiment. Our simulations reveal that the initial excitation to the 1 1 B u state rapidly evolves via wavepacket dynamics that follow both bright- and dark-state pathways as well as mixtures of these. In order to test the sensitivity of the AIMS results to the relative ordering of states, we considered two hypothetical scenarios biased toward either the bright 1 B u or the dark 2 1 A g state. In contrast with AIMS/SA-3-CAS(4/4)-MSPT2 simulations, neither of these scenarios yields favorable agreement with experiment. Thus, we conclude that the excited state non-adiabatic dynamics in BD involves both of these ultrafast pathways.

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

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.

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

Electrothermal atomization laser-excited atomic fluorescence spectroscopy for the determination of indium

International Nuclear Information System (INIS)

Aucelio, R.Q.; Smith, B.W.; Winefordner, J.D.

1998-01-01

A dye laser pumped by a high-repetition-rate copper vapor laser was used as the excitation source to determine indium at parts-per-trillion level by electrothermal atomization laser-excited atomic fluorescence spectrometry (ETA-LEAFS). A comparison was made between wall atomization, in pyrolytic and nonpyrolytic graphite tubes, and platform atomization. The influence of several chemical modifiers either in solution or precoated in the graphite tube was evaluated. The influence of several acids and NaOH in the analyte solution was also studied. Optimization of the analytical conditions was carried out to achieve the best signal-to-background ratio and consequently an absolute limit of detection of 1 fg. Some possible interferents of the method were evaluated. The method was evaluated by determining indium in blood, urine, soil, and urban dust samples. Recoveries between 99.17 and 109.17% are reported. A precision of 4.1% at the 10 ng g -1 level in water standards was achieved. copyright 1998 Society for Applied Spectroscopy

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.

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

Coulomb Excitation of a Neutron-Rich $^{88}$Kr Beam Search for Mixed Symmetry States

CERN Multimedia

Andreoiu, C; Napiorkowski, P J; Iwanicki, J S

2002-01-01

We propose to use the ISOLDE/REX/MINIBALL/CD set-up to perform a Coulomb Excitation experiment with a $^{88}$Kr radioactive beam. The motivation includes a search for $Mixed$ $Symmetry$ states predicted by the IBM-2 model, gathering more spectroscopy data about the $^{88}$Kr nucleus and extending shape coexistence studies (performed previously by the proposers for neutron-deficient Kr isotopes) to the neutron-rich side. The proposed experiment will provide data complementary to the Coulomb Excitation of a relativistic $^{88}$Kr beam proposed by D. Tonev et al. for a RISING experiment. A total of 12 days of beam time is necessary for the experiment, equally divided into two runs. One run with a 2.2 MeV/A beam energy on a $^{48}$Ti target and a second run with the maximum available REX energy of 3.1 MeV/A on a $^{208}$Pb target are requested. Using either a UC$_{x}$ or ThC$_{x}$ fissioning primary target coupled with a plasma source by a cooled transfer line seems to be the best choice for the proposed experime...

Anomalous behavior of the excited state of the A exciton in bulk WS2

DEFF Research Database (Denmark)

Jindal, Vishwas; Bhuyan, Sumi; Deilmann, Thorsten

2018-01-01

Results of optical spectroscopy studies on bulk 2H-WS2 at energies close to its direct band gap are presented. Reflectance and absorption measurements at low temperature show only one dominant feature due to the A exciton of bulk WS2 at similar to 2.02 eV. However, a laser-modulated photoreflecta......Results of optical spectroscopy studies on bulk 2H-WS2 at energies close to its direct band gap are presented. Reflectance and absorption measurements at low temperature show only one dominant feature due to the A exciton of bulk WS2 at similar to 2.02 eV. However, a laser....... The experimental results are analyzed by comparison with many-body perturbation theory calculations, including the solutions of the Bethe-Salpeter equation. A* is identified as the first excited state of the A exciton, that is, A(n = 2). The anomalous behavior of A* is explained by its distinct wave function...... spread along the c axis, the direction of weak van der Waals bonding, which makes it more susceptible to perturbations. Our ab initio calculations suggest that the A exciton in the ground state has a two-dimensional (2D) nature with a large binding energy E-b, in fair agreement with E-b similar to 90...

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.)

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.

Two-dimensional infrared spectroscopy of vibrational polaritons.

Science.gov (United States)

Xiang, Bo; Ribeiro, Raphael F; Dunkelberger, Adam D; Wang, Jiaxi; Li, Yingmin; Simpkins, Blake S; Owrutsky, Jeffrey C; Yuen-Zhou, Joel; Xiong, Wei

2018-04-19

We report experimental 2D infrared (2D IR) spectra of coherent light-matter excitations--molecular vibrational polaritons. The application of advanced 2D IR spectroscopy to vibrational polaritons challenges and advances our understanding in both fields. First, the 2D IR spectra of polaritons differ drastically from free uncoupled excitations and a new interpretation is needed. Second, 2D IR uniquely resolves excitation of hybrid light-matter polaritons and unexpected dark states in a state-selective manner, revealing otherwise hidden interactions between them. Moreover, 2D IR signals highlight the impact of molecular anharmonicities which are applicable to virtually all molecular systems. A quantum-mechanical model is developed which incorporates both nuclear and electrical anharmonicities and provides the basis for interpreting this class of 2D IR spectra. This work lays the foundation for investigating phenomena of nonlinear photonics and chemistry of molecular vibrational polaritons which cannot be probed with traditional linear spectroscopy.

Single-particle spectroscopy of I-III-VI semiconductor nanocrystals: spectral diffusion and suppression of blinking by two-color excitation.

Science.gov (United States)

Sharma, Dharmendar Kumar; Hirata, Shuzo; Bujak, Lukasz; Biju, Vasudevanpillai; Kameyama, Tatsuya; Kishi, Marino; Torimoto, Tsukasa; Vacha, Martin

2016-07-14

Ternary I-III-VI semiconductor nanocrystals have been explored as non-toxic alternatives to II-VI semiconductors for optoelectronic and sensing applications, but large photoluminescence spectral width and moderate brightness restrict their practical use. Here, using single-particle photoluminescence spectroscopy on nanocrystals of (AgIn)xZn2(1-x)S2 we show that the photoluminescence band is inhomogeneously broadened and that size distribution is the dominant factor in the broadening. The residual homogeneous linewidth of individual nanocrystals reaches up to 75% of the ensemble spectral width. Single nanocrystals undergo spectral diffusion which also contributes to the inhomogeneous band. Excitation with two lasers with energies above and below the bandgap reveals coexistence of two emitting donor states within one particle. Spectral diffusion in such particles is due to temporal activation and deactivation of one such state. Filling of a trap state with a lower-energy laser enables optical modulation of photoluminescence intermittency (blinking) and leads to an almost two-fold increase in brightness.

Handbook of Applied Solid State Spectroscopy

CERN Document Server

Vij, D. R

2006-01-01

Solid-State spectroscopy is a burgeoning field with applications in many branches of science, including physics, chemistry, biosciences, surface science, and materials science. Handbook of Applied Solid-State Spectroscopy brings together in one volume information about various spectroscopic techniques that is currently scattered in the literature of these disciplines. This concise yet comprehensive volume covers theory and applications of a broad range of spectroscopies, including NMR, NQR, EPR/ESR, ENDOR, scanning tunneling, acoustic resonance, FTIR, auger electron emission, x-ray photoelectron emission, luminescence, and optical polarization, and more. Emphasis is placed on fundamentals and current methods and procedures, together with the latest applications and developments in the field.

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

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.

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...

Numerical simulations of oscillating soliton stars: Excited states in spherical symmetry and ground state evolutions in 3D

International Nuclear Information System (INIS)

Balakrishna, Jayashree; Bondarescu, Ruxandra; Daues, Gregory; Bondarescu, Mihai

2008-01-01

Excited state soliton stars are studied numerically for the first time. The stability of spherically symmetric S-branch excited state oscillatons under radial perturbations is investigated using a 1D code. We find that these stars are inherently unstable either migrating to the ground state or collapsing to black holes. Higher excited state configurations are observed to cascade through intermediate excited states during their migration to the ground state. This is similar to excited state boson stars [J. Balakrishna, E. Seidel, and W.-M. Suen, Phys. Rev. D 58, 104004 (1998).]. Ground state oscillatons are then studied in full 3D numerical relativity. Finding the appropriate gauge condition for the dynamic oscillatons is much more challenging than in the case of boson stars. Different slicing conditions are explored, and a customized gauge condition that approximates polar slicing in spherical symmetry is implemented. Comparisons with 1D results and convergence tests are performed. The behavior of these stars under small axisymmetric perturbations is studied and gravitational waveforms are extracted. We find that the gravitational waves damp out on a short time scale, enabling us to obtain the complete waveform. This work is a starting point for the evolution of real scalar field systems with arbitrary symmetries

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.

Probing the Vibrational Spectroscopy of the Deprotonated Thymine Radical by Photodetachment and State-Selective Autodetachment Photoelectron Spectroscopy via Dipole-Bound States

Science.gov (United States)

Huang, Dao-Ling; Zhu, Guo-Zhu; Wang, Lai-Sheng

2016-06-01

Deprotonated thymine can exist in two different forms, depending on which of its two N sites is deprotonated: N1[T-H]^- or N3[T-H]^-. Here we report a photodetachment study of the N1[T-H]^- isomer cooled in a cryogenic ion trap and the observation of an excited dipole-bound state. Eighteen vibrational levels of the dipole-bound state are observed, and its vibrational ground state is found to be 238 ± 5 wn below the detachment threshold of N1[T-H]^-. The electron affinity of the deprotonated thymine radical (N1[T-H]^.) is measured accruately to be 26 322 ± 5 wn (3.2635 ± 0.0006 eV). By tuning the detachment laser to the sixteen vibrational levels of the dipole-bound state that are above the detachment threshold, highly non-Franck-Condon resonant-enhanced photoelectron spectra are obtained due to state- and mode-selective vibrational autodetachment. Much richer vibrational information is obtained for the deprotonated thymine radical from the photodetachment and resonant-enhanced photoelectron spectroscopy. Eleven fundamental vibrational frequencies in the low-frequency regime are obtained for the N1[T-H]^. radical, including the two lowest-frequency internal rotational modes of the methyl group at 70 ± 8 wn and 92 ± 5 wn. D. L. Huang, H. T. Liu, C. G. Ning, G. Z. Zhu and L. S. Wang, Chem. Sci., 6, 3129-3138 (2015)

Laser excitation of the n=3 level of positronium for antihydrogen production

CERN Document Server

Aghion, S; Ariga, A; Ariga, T; Bonomi, G; Braunig, P; Bremer, J; Brusa, R S; Cabaret, L; Caccia, M; Caravita, R; Castelli, F; Cerchiari, G; Chlouba, K; Cialdi, S; Comparat, D; Consolati, G; Demetrio, A; Di Noto, L; Doser, M; Dudarev, A; Ereditato, A; Evans, C; Ferragut, R; Fesel, J; Fontana, A; Forslund, O K; Gerber, S; Giammarchi, M; Gligorova, A; Gninenko, S N; Guatieri, F; Haider, S; Holmestad, H; Huse, T; Jernelv, I L; Jordan, E; Kellerbauer, A; Kimura, M; Koetting, T; Krasnicky, D; Lagomarsino, V; Lansonneur, P; Lebrun, P; Lehner, S; Liberadzka, J; Malbrunot, C; Mariazzi, S; Marx, L; Matveev, V A; Mazzotta, Z; Nebbia, G; Nedelec, P; Oberthaler, M K; Pacifico, N; Pagano, D; Penasa, L; Petracek, V; Pistillo, C; Prelz, F; Prevedelli, M; Ravelli, L; Resch, L; Rienacker, B; Røhne, O M; Rotondi, A; Sacerdoti, M; Sandaker, H; Santoro, R; Scampoli, P; Smestad, L; Sorrentino, F; Spacek, M; Storey, J; Strojek, I M; Testera, G; Tietje, I; Vamosi, S; Widmann, E; Yzombard, P; Zmeskal, J; Zurlo, N.

2016-01-01

We demonstrate laser excitation of the n=3 state of positronium (Ps) in vacuum. A specially designed high-efficiency pulsed slow positron beam and single shot positronium annihilation lifetime spectroscopy were used to produce and detect Ps. Pulsed laser excitation of n=3 level at 205 nm was monitored via Ps photoionization induced by a second intense laser pulse at 1064 nm. About 15% of the overall positronium emitted in vacuum was excited to n=3 and photoionized. Saturation of both the n=3 excitation and the following photoionization was observed and is explained by a simple rate equation model. Scanning the laser frequency allowed us to extract the positronium transverse temperature related to the width of the Doppler-broadened line. Moreover, preliminary observation of excitation to Rydberg states (n = 15...17) using n=3 as intermediate level was observed, giving an independent confirmation of efficient excitation to the 33P state.

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.

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.)

Ultrafast photoelectron spectroscopy of small molecule organic films

Science.gov (United States)

Read, Kendall Laine

As research in the field of ultrafast optics has produced shorter and shorter pulses, at an ever-widening range of frequencies, ultrafast spectroscopy has grown correspondingly. In particular, ultrafast photoelectron spectroscopy allows direct observation of electrons in transient or excited states, regardless of the eventual relaxation mechanisms. High-harmonic conversion of 800nm, femtosecond, Ti:sapphire laser pulses allows excite/probe spectroscopy down into atomic core level states. To this end, an ultrafast, X-UV photoelectron spectroscopic system is described, including design considerations for the high-harmonic generation line, the time of flight detector, and the subsequent data collection electronics. Using a similar experimental setup, I have performed several ultrafast, photoelectron excited state decay studies at the IBM, T. J. Watson Research Center. All of the observed materials were electroluminescent thin film organics, which have applications as the emitter layer in organic light emitting devices. The specific materials discussed are: Alq, BAlq, DPVBi, and Alq doped with DCM or DMQA. Alq:DCM is also known to lase at low photoexcitation thresholds. A detailed understanding of the involved relaxation mechanisms is beneficial to both applications. Using 3.14 eV excite, and 26.7 eV probe, 90 fs laser pulses, we have observed the lowest unoccupied molecular orbital (LUMO) decay rate over the first 200 picoseconds. During this time, diffusion is insignificant, and all dynamics occur in the absence of electron transport. With excitation intensities in the range of 100μJ/cm2, we have modeled the Alq, BAlq, and DPVBi decays via bimolecular singlet-singlet annihilation. At similar excitations, we have modeled the Alq:DCM decay via Förster transfer, stimulated emission, and excimeric formation. Furthermore, the Alq:DCM occupied to unoccupied molecular orbital energy gap was seen to shrink as a function of excite-to-probe delay, in accordance with the

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

2012 ELECTRONIC SPECTROSCOPY & DYNAMICS GORDON RESEARCH CONFERENCE, JULY 22-27, 2012

Energy Technology Data Exchange (ETDEWEB)

Kohler, Bern

2012-07-27

Topics covered in this GRC include high-resolution spectroscopy, coherent electronic energy transport in biology, excited state theory and dynamics, excitonics, electronic spectroscopy of cold and ultracold molecules, and the spectroscopy of nanostructures. Several sessions will highlight innovative techniques such as time-resolved x-ray spectroscopy, frequency combs, and liquid microjet photoelectron spectroscopy that have forged stimulating new connections between gas-phase and condensed-phase work.

The Raman effect and its application to electronic spectroscopies in metal-centered species : Techniques and investigations in ground and excited states

NARCIS (Netherlands)

Browne, W.R.; J. McGarvey, J.

In the decades since its discovery and somewhat limited early applications, Raman scattering has become the basis for the development of a variety of methods for probing molecular structure both in ground and electronically excited states. In this review, following a brief look at the underlying

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

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.

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

Spin-polarized spin excitation spectroscopy

International Nuclear Information System (INIS)

Loth, Sebastian; Lutz, Christopher P; Heinrich, Andreas J

2010-01-01

We report on the spin dependence of elastic and inelastic electron tunneling through transition metal atoms. Mn, Fe and Cu atoms were deposited onto a monolayer of Cu 2 N on Cu(100) and individually addressed with the probe tip of a scanning tunneling microscope. Electrons tunneling between the tip and the substrate exchange energy and spin angular momentum with the surface-bound magnetic atoms. The conservation of energy during the tunneling process results in a distinct onset threshold voltage above which the tunneling electrons create spin excitations in the Mn and Fe atoms. Here we show that the additional conservation of spin angular momentum leads to different cross-sections for spin excitations depending on the relative alignment of the surface spin and the spin of the tunneling electron. For this purpose, we developed a technique for measuring the same local spin with a spin-polarized and a non-spin-polarized tip by exchanging the last apex atom of the probe tip between different transition metal atoms. We derive a quantitative model describing the observed excitation cross-sections on the basis of an exchange scattering process.

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

Coulomb excitation

International Nuclear Information System (INIS)

McGowan, F.K.; Stelson, P.H.

1974-01-01

The theory of Coulomb excitation and a brief review of pertinent treatments of the Coulomb excitation process that are useful for the analysis of experiments are given. Examples demonstrating the scope of nuclear structure information obtainable from gamma spectroscopy are presented. Direct Elambda excitation of 232 Th is discussed in terms of the one phonon octupole vibrational spectrum. B(MI) reduced transition probabilities resulting from Coulomb excitation of odd-A deformed nuclei with heavy ions are presented as a test of the rotational model. The use of gamma ray coincidence and particle-gamma coincidence as tools for investigating Coulomb excitation is discussed. (U.S.)

Excited state dynamics in In0.5Al0.04Ga0.46As/Al0.08Ga0.92As self-assembled quantum dots

DEFF Research Database (Denmark)

Smith, L.M.; Leosson, Kristjan; Østergaard, John Erland

2001-01-01

We use time-resolved photoluminescence spectroscopy to probe the relaxation of excited states in In0.5Al0.04Ga0.40As/Al0.08Ga0.92As self-assembled quantum dots. The relaxation rate of excitons confined to the quantum dots increases by nearly an order of magnitude as the energy of the states...... approaches the top of the quantum dot potential. This dramatic change in the dynamics of these states reflects the increasing complexity of the states localized near the top of the quantum dots....

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.; Xiao, Dequan; Batista, Victor S.; Nibbering, Erik Theodorus Johannes

2014-01-01

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

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)

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.)

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....

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)

Polarized fine structure in the excitation spectrum of a negatively charged quantum dot

OpenAIRE

Ware, M. E.; Stinaff, E. A.; Gammon, D.; Doty, M. F.; Bracker, A. S.; Gershoni, D.; Korenev, V. L.; Badescu, S. C.; Lyanda-Geller, Y.; Reinecke, T. L.

2005-01-01

We report polarized photoluminescence excitation spectroscopy of the negative trion in single charge tunable InAs/GaAs quantum dots. The spectrum exhibits a p-shell resonance with polarized fine structure arising from the direct excitation of the electron spin triplet states. The energy splitting arises from the axially symmetric electron-hole exchange interaction. The magnitude and sign of the polarization are understood from the spin character of the triplet states and a small amount of qua...

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.

Organic Linker Defines the Excited-State Decay of Photocatalytic MIL-125(Ti)-Type Materials.

Science.gov (United States)

Santaclara, Jara G; Nasalevich, Maxim A; Castellanos, Sonia; Evers, Wiel H; Spoor, Frank C M; Rock, Kamila; Siebbeles, Laurens D A; Kapteijn, Freek; Grozema, Ferdinand; Houtepen, Arjan; Gascon, Jorge; Hunger, Johannes; van der Veen, Monique A

2016-02-19

Recently, MIL-125(Ti) and NH2 -MIL-125(Ti), two titanium-based metal-organic frameworks, have attracted significant research attention in the field of photocatalysis for solar fuel generation. This work reveals that the differences between these structures are not only based on their light absorption range but also on the decay profile and topography of their excited states. In contrast to MIL-125(Ti), NH2 -MIL-125(Ti) shows markedly longer lifetimes of the charge-separated state, which improves photoconversion by the suppression of competing decay mechanisms. We used spectroelectrochemistry and ultrafast spectroscopy to demonstrate that upon photoexcitation in NH2 -MIL-125(Ti) the electron is located in the Ti-oxo clusters and the hole resides on the aminoterephthalate unit, specifically on the amino group. The results highlight the role of the amino group in NH2 -MIL-125(Ti), the electron donation of which extends the lifetime of the photoexcited state substantially. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Excited State Assignment and Laser Action in π-Conjugated Polymers

Science.gov (United States)

Vardeny, Z. V.

1998-03-01

We have applied a variety of ps transient and cw spectroscopies to elucidate the ground and excited electronic states of luminescent and nonluminescent thin films and solutions of π-conjugated polymers. These techniques include photoinduced absorption (PA), photoluminescence (PL), resonant Raman scattering (RRS), electro-absorption (EA), two photon absorption (TPA), and PA detected magnetic resonance. We found that the luminescence efficiency, the resonant and subgap third-order nonlinear optical properties and the RRS dispersion in these polymers are determined by the energies and symmetries of a subset of the excited states, including a series of singlet excitons with odd (B_u) and even (A_g) parity lying below a continuum band. Among them, the lowest Bu exciton (1B_u) and two other dominant Ag excitons (mAg and kA_g) are particularly important in determining the EA, TPA, and excitonic ps PA spectra.(S.V. Frolov, M. Liess, P.A. Lane, W. Gellermann, Z.V. Vardeny, M. Ozaki, and K. Yoshino, Phys. Rev. Lett). 78, 4285 (1997). We also found(M. Ozaki, E. Ehrenfreund, R.E. Benner, T.J. Baron, K. Yoshino, and Z.V. Vardeny, Phys. Rev. Lett). 79, 1762 (1997). that the RRS phonon dispersion with the laser excitation energy is governed by the dependence of lowest Ag exciton (2A_g) on the chain length distribution in the polymer. This leads to stronger RRS dispersion in nonluminescent polymers. Moreover the relative energies of the 1Bu and 2Ag excitons determine the PL quantum efficiency η, regardless of the ground state degeneracy. If E(2A_g) < E(1B_u) then η is small because of the dipole forbidden character of the lowest singlet. We will give examples of nonluminescent polymers which belong to this class with both degenerate and nondegenerate ground state, respectively. On the other hand, if E(1B_u) < E(2A_g) then η is large and the polymer might be considered as active material for display applications. Again we give examples of highly luminescent polymers with

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.

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

In-beam gamma spectroscopy of /sup 82/Sr

CERN Document Server

Dewald, A; Gelberg, A; Kaup, U; Von Brentano, P; Zell, K O

1981-01-01

The excited levels of /sup 82/Sr have been investigated by means of in-beam gamma-ray spectroscopy via the reactions /sup 72/Ge(/sup 12/C, 2n), /sup 66/Zn(/sup 19/F, p2n), and /sup 79/Br(/sup 6/Li, 3n). Lifetimes of excited states were measured by the recoil distance method. Excitation energies and B(E2) values have been compared with calculations using the Interacting Boson Model. (19 refs).

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

Development of a Stair-Step Multifrequency Synchronized Excitation Signal for Fast Bioimpedance Spectroscopy

Science.gov (United States)

Bian, He; Du, Fangling; Sun, Qiang

2014-01-01

Wideband excitation signal with finite prominent harmonic components is desirable for fast bioimpedance spectroscopy (BIS) measurements. This work introduces a simple method to synthesize and realize a type of periodical stair-step multifrequency synchronized (MFS) signal. The Fourier series analysis shows that the p-order MFS signal f(p, t) has constant 81.06% energy distributed equally on its p  2nth primary harmonics. The synthesis principle is described firstly and then two examples of the 4-order and 5-order MFS signals, f(4, t) and f(5, t), are synthesized. The method to implement the MFS waveform based on a field-programmable gate array (FPGA) and a digital to analog converter (DAC) is also presented. Both the number and the frequencies of the expected primary harmonics can be adjusted as needed. An impedance measurement experiment on a RC three-element equivalent model is performed, and results show acceptable precision, which validates the feasibility of the MFS excitation. PMID:24701563

Development of a Stair-Step Multifrequency Synchronized Excitation Signal for Fast Bioimpedance Spectroscopy

Directory of Open Access Journals (Sweden)

Yuxiang Yang

2014-01-01

Full Text Available Wideband excitation signal with finite prominent harmonic components is desirable for fast bioimpedance spectroscopy (BIS measurements. This work introduces a simple method to synthesize and realize a type of periodical stair-step multifrequency synchronized (MFS signal. The Fourier series analysis shows that the p-order MFS signal f(p,t has constant 81.06% energy distributed equally on its p  2nth primary harmonics. The synthesis principle is described firstly and then two examples of the 4-order and 5-order MFS signals, f(4,t and f(5,t, are synthesized. The method to implement the MFS waveform based on a field-programmable gate array (FPGA and a digital to analog converter (DAC is also presented. Both the number and the frequencies of the expected primary harmonics can be adjusted as needed. An impedance measurement experiment on a RC three-element equivalent model is performed, and results show acceptable precision, which validates the feasibility of the MFS excitation.

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.

Study of the electronic structure of pure aluminium, aluminium oxide and nitride by spectroscopy of electrons excited under electronic and photonic bombardment (X and UV)

International Nuclear Information System (INIS)

Gautier-Soyer, Martine

1985-01-01

This research thesis reports the use of electron spectroscopy with electrons excited under electronic or photonic (X or UV) bombardment for the study of electronic state density of aluminium, aluminium oxide (Al 2 O 3 ) and aluminium nitride (AlN). The objective is to get an insight into phenomena related to technological problems of adherence, wear, lubrication, corrosion or breakdown met in metals, insulators and semiconductors. The author highlighted the presence of occupied surface states on Al(111) and Al(100), and electronic levels localised in the forbidden band of Al 2 O 3 and AlN, induced by structural defects which promote surface reactivity [fr

Optical spectroscopy of orbital and magnetic excitations in vanadates and cuprates

Energy Technology Data Exchange (ETDEWEB)

Benckiser, Eva Vera

2007-10-15

Within the scope of this thesis, the low-energy excitations of undoped Mott insulators RVO{sub 3} with R = Y, Ho, and Ce, (Sr,Ca)CuO{sub 2} and La{sub 8}Cu{sub 7}O{sub 19} have been investigated by means of optical spectroscopy. The compounds RVO{sub 3} with R=rare-earth ion recently have attracted a lot of interest because of their unusual structural, orbital, and magnetic properties. The compounds undergo a series of temperatureinduced phase transitions accompanied by a change of orbital and magnetic order. Furthermore, it has been proposed that YVO{sub 3} represents the first realization of a one-dimensional orbital liquid and an orbital Peierls phase, with a transition to an orbitally ordered phase at lower temperatures. In this thesis, we present the optical conductivity {sigma}({omega}) of RVO{sub 3} with R=Y, Ho, and Ce for energies from 0.1 to 1.6 eV as a function of temperature (10-300 K) and polarization of the incident light parallel to the crystallographic axes ({sigma}{sub a},{sigma}{sub b},{sigma}{sub c}). Our main experimental result is the observation of two absorption features at 0.55 eV in {sigma}{sub a}({omega}) and 0.4 eV in {sigma}{sub c}({omega}) which are assigned to collective orbital excitations, in contrast to conventional local crystal-field transitions. Altogether, our results strongly suggest that in RVO{sub 3} with R=Y, Ho, and Ce the orbital exchange interactions play a decisive role. In a second study, we have investigated the magnetic excitations of low-dimensional quantum magnets, namely the spin chain (Sr,Ca)CuO{sub 2} and the five-leg ladder La{sub 8}Cu{sub 7}O{sub 19}. For (Sr,Ca)CuO{sub 2}, two absorption features around 0.4 eV in {sigma}{sub c}({omega}) (chain direction) and {sigma}{sub b}({omega}) (inter-chain direction) are identified as magnetic contributions to the optical conductivity. The analysis of {sigma}{sub c}({omega}) enables the very precise determination of the nearest-neighbor exchange coupling J{sub c} as a

Interrogating the vibrational relaxation of highly excited polyatomics with time-resolved diode laser spectroscopy: C6H6, C6D6, and C6F6+CO2

International Nuclear Information System (INIS)

Sedlacek, A.J.; Weston, R.E. Jr.; Flynn, G.W.

1991-01-01

The vibrational relaxation of highly excited ground state benzene, benzene d 6 , and hexafluorobenzene by CO 2 has been investigated with high resolution diode laser spectroscopy. The vibrationally hot polyatomics are formed by single photon 248 nm excitation to the S 1 state followed by rapid radiationless transitions. It has been found that in all cases less than 1% of the energy initially present in the polyatomics is deposited into the high frequency mode of CO 2 (ν 3 ). An investigation of the CO 2 (00 0 1) nascent rotational distribution under single collision conditions reveals that very little rotational excitation accompanies vibrational energy transfer to the ν 3 mode. The CO 2 (ν 3 ) rotational states can be described by temperatures, T rot , as follows: C 6 H 6 , T rot =360±30 K; C 6 D 6 , T rot =350±35 K and C 6 F 6 , T rot =340±23 K. An estimate of left-angle ΔE right-angle ν3 , the mean energy transferred to the CO 2 ν 3 mode per collision, suggests that as the availability of low frequency modes in the excited molecule increases, less energy is deposited into the high frequency mode of CO 2 . Finally, evidence is presented suggesting that even at moderate laser fluences, the two-photon ionization of benzene can lead to substantial CO 2 ν 3 excitation via electron+CO 2 inelastic collisions

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

Laser photoelectron spectroscopy of MnH - and FeH - : Electronic structures of the metal hydrides, identification of a low-spin excited state of MnH, and evidence for a low-spin ground state of FeH

Science.gov (United States)

Stevens, Amy E.; Feigerle, C. S.; Lineberger, W. C.

1983-05-01

The laser photoelectron spectra of MnH- and MnD-, and FeH- and FeD- are reported. A qualitative description of the electronic structure of the low-spin and high-spin states of the metal hydrides is developed, and used to interpret the spectra. A diagonal transition in the photodetachment to the known high-spin, 7Σ+, ground state of MnH is observed. An intense off-diagonal transition to a state of MnH, at 1725±50 cm-1 excitation energy, is attributed to loss of an antibonding electron from MnH-, to yield a low-spin quintet state of MnH. For FeH- the photodetachment to the ground state is an off-diagonal transition, attributed to loss of the antibonding electron from FeH-, to yield a low-spin quartet ground state of FeH. A diagonal transition results in an FeH state at 1945±55 cm-1; this state of FeH is assigned as the lowest-lying high-spin sextet state of FeH. An additional excited state of MnH and two other excited states of FeH are observed. Excitation energies for all the states are reported; vibrational frequencies and bond lengths for the ions and several states of the neutrals are also determined from the spectra. The electron affinity of MnH is found to be 0.869±0.010 eV; and the electron affinity of FeH is determined to be 0.934±0.011 eV. Spectroscopic constants for the various deuterides are also reported.

Photoelectron spectroscopy

International Nuclear Information System (INIS)

Shirley, D.A.

1976-01-01

Research activities in photoelectron spectroscopy at Lawrence Radiation Laboratory during 1976 are described. Topics covered include: the orientation of CO on Pt(III) and Ni(III) surfaces from angle-resolved photoemission; photoemission from CO on Pt(III) in the range 40 eV less than or equal to dirac constant ω less than or equal to 150 eV; photoemission studies of electron states at clean surfaces using synchrotron radiation; angle and energy dependent photoemission studies of plasmon loss structure in Al and In; d-orbital directed photoemission from copper; interpretation of angle-resolved x-ray photoemission from valence bands; atomic cross-section effects in soft x-ray photoemission from Ag, Au, and Pt valence bands; x-ray photoelectron spectroscopic studies of the electronic structure of transition metal difluorides; x-ray photoemission investigation of the density of states of B'-NiAl; the electronic structure of SrTiO 3 and some simple related oxides; fluorescence lifetime measurements of np 5 (n+1)S' states in krypton and xenon; Zeeman beats in the resonance fluorescence of the 3P 1 , states in krypton and xenon; lifetime measurements of rare-gas dimers; configuration interaction effects in the atomic photoelectron spectra of Ba, Sm, Eu, and Yb; glow discharge lamps as electron sources for electron impact excitation; electron impact excitation of electron correlation states in Ca, Sr, and Ba; photoelectron spectroscopy of atomic and molecular bismuth; relativistic effects in the uv photoelectron spectra of group VI diatomic molecules; and relative gas-phase acidities and basicities from a proton potential model

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.

Valence universal multireference coupled cluster calculations of the properties of indium in its ground and excited states

International Nuclear Information System (INIS)

Das, Madhulita; Chaudhuri, Rajat K; Chattopadhyay, Sudip; Sinha Mahapatra, Uttam

2011-01-01

In view of its importance in high precision spectroscopy, the valence universal multireference coupled cluster (VU-MRCC) method with four-component relativistic spinors has been applied to compute ionization potential (IP) and excitation energies (EEs) of the indium atom (In I). The effect of electron correlations on the ground and excited state properties is investigated using different levels of CC approximations and basis sets. This study reveals that for a given basis, the linearized VU-MRCC method tends to underestimate the IP, EEs and other one-electron properties such as magnetic hyperfine constant (A) compared to the full blown VU-MRCC method. Our computed results have been compared with available theoretical and experimental data. The IP, EEs, A and oscillator strengths (f) determined at the VU-MRCC level are in excellent agreement with the experimental results. The properties reported here further demonstrate that a basis set with at least h-type of orbitals is ubiquitous to achieve converged results.

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)

Precision spectroscopy of the 2S-4P{sub 1/2} transition in atomic hydrogen on a cold thermal beam of optically excited 2S atoms

Energy Technology Data Exchange (ETDEWEB)

Beyer, Axel; Kolachevsky, Nikolai; Alnis, Janis; Yost, Dylan C.; Matveev, Arthur; Parthey, Christian G.; Pohl, Randolf; Udem, Thomas [Max-Planck-Institut fuer Quantenoptik, 85748 Garching (Germany); Khabarova, Ksenia [FSUE ' VNIIFTRI' , 141570 Moscow (Russian Federation); Haensch, Theodor W. [Max-Planck-Institut fuer Quantenoptik, 85748 Garching (Germany); Ludwig-Maximilians-Universitaet, 80799 Muenchen (Germany)

2013-07-01

The 'proton size puzzle', i.e. the discrepancy between the values for the proton r.m.s. charge radius deduced from precision spectroscopy of atomic hydrogen and electron-proton-scattering on one side and the value deduced from muonic hydrogen spectroscopy on the other side, has been persisting for more than two years now. Although huge efforts have been put into trying to resolve this discrepancy from experimental and theoretical side, no convincing argument could be found so far. In this talk, we report on a unique precision spectroscopy experiment on atomic hydrogen, which is aiming to bring some light to the hydrogen part of the puzzle: In contrast to any previous high resolution experiment probing a transition frequency between the meta-stable 2S state and a higher lying nL state (n=3,4,6,8,12, L=S,P,D), our measurement of the 2S-4P{sub 1/2} transition frequency is the first experiment being performed on a cold thermal beam of hydrogen atoms optically excited to the 2S state. We will discuss how this helps to efficiently suppresses leading systematic effects of previous measurements and present the preliminary results we obtained so far.

Excited states in stochastic electrodynamics

International Nuclear Information System (INIS)

Franca, H.M.; Marshall, T.W.

1987-12-01

It is shown that the set of Wigner functions associated with the excited states of the harmonic oscillator constitute a complete set of functions over the phase space. An arbitraty distribution can be expanded in terms of these Wigner functions. By studying the time evolution, according to Stochastic Electrodynamics, of the expansion coefficients, becomes feasible to separate explicity the contributionsof the radiative reaction and the vaccuum field to the Einsten. A coefficients for this system. A simple semiclassical explanation of the Weisskopf-Heitler phenomenon in resonance fluorescence is also supplied. (author) [pt

A strong steric hindrance effect on ground state, excited state, and charge separated state properties of a CuI-diimine complex captured by X-ray transient absorption spectroscopy