The Experts below are selected from a list of 31653 Experts worldwide ranked by ideXlab platform
Viatcheslav Kokoouline - One of the best experts on this subject based on the ideXlab platform.
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proposal for a laser control of Vibrational cooling in na 2 using resonance coalescence
Physical Review Letters, 2011Co-Authors: O Atabek, Olivier Dulieu, Viatcheslav Kokoouline, R Lefebvre, Maxence Lepers, Amine JaouadiAbstract:With a specific choice of laser parameters resulting in a so-called exceptional point (EP) in the wavelength-intensity parameter plane, it is possible to produce the coalescence of two Floquet resonances describing the photodissociation of the ${\mathrm{Na}}_{2}$ molecule, which is one of the candidates for the formation of samples of translationally cold molecules. By appropriately tuning laser parameters along a contour encircling the exceptional point, the resonances exchange their quantum nature. Thus a laser-controlled transfer of the probability density from one field-free Vibrational Level to another is achieved through adiabatic transport involving these resonances. We propose an efficient scenario for Vibrational cooling of ${\mathrm{Na}}_{2}$ referring to cascade transfers involving multiple EPs and predicted to be robust up to a 78% rate against laser-induced dissociation.
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calculation of rate constants for Vibrational and rotational excitation of the h 3 ion by electron impact
Monthly Notices of the Royal Astronomical Society, 2010Co-Authors: Viatcheslav Kokoouline, Jonathan Tennyson, Alexandre Faure, Chris H GreeneAbstract:We present theoretical thermally averaged rate constants for Vibrational and rotational (de-)excitation of the H + 3 ion by electron impact. The constants are calculated using the multichannel quantum-defect approach. The calculation includes processes that involve a change |ΔJ| ≤ 2 in the rotational angular momentum J of H + 3 . The rate constants are calculated for states with J ≤ 5 for rotational transitions of the H + 3 ground Vibrational Level. The thermal rates for transitions among the lowest eight Vibrational Levels are also presented, averaged over the rotational structure of the Vibrational Levels. The conditions for producing non-thermal rotational and Vibrational distributions of H + 3 in astrophysical environments are discussed.
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calculation of rate constants for Vibrational and rotational excitation of the h3 ion by electron impact
arXiv: Atomic Physics, 2010Co-Authors: Viatcheslav Kokoouline, Jonathan Tennyson, Alexandre Faure, Chris H GreeneAbstract:We present theoretical thermally-averaged rate constants for Vibrational and rotational (de-)excitation of the H3+ ion by electron impact. The constants are calculated using the multi-channel quantum-defect approach. The calculation includes processes that involve a change Delta J<=2 in the rotational angular momentum J of H3+. The rate constants are calculated for states with J<=5 for rotational transitions of the H3+ ground Vibrational Level. The thermal rates for transitions among the lowest eight Vibrational Levels are also presented, averaged over the rotational structure of the Vibrational Levels. The conditions for producing non-thermal rotational and Vibrational distributions of H3+ in astrophysical environments are discussed.
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dissociative recombination of h3 in the ground and excited Vibrational states
Journal of Chemical Physics, 2007Co-Authors: Samantha Fonseca Dos Santos, Viatcheslav Kokoouline, Chris H GreeneAbstract:The article presents calculated dissociative recombination (DR) rate coefficients for H3+. The previous theoretical work on H3+ was performed using the adiabatic hyperspherical approximation to calculate the target ion Vibrational states and it considered just a limited number of ionic rotational states. In this study, we use accurate Vibrational wave functions and a larger number of possible rotational states of the H3+ ground Vibrational Level. The DR rate coefficient obtained is found to agree better with the experimental data from storage ring experiments than the previous theoretical calculation. We present evidence that excited rotational states could be playing an important role in those experiments for collision energies above 10meV. The DR rate coefficients calculated separately for ortho- and para-H3+ are predicted to differ significantly at low energy, a result consistent with a recent experiment. We also present DR rate coefficients for Vibrationally excited initial states of H3+, which are fo...
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dissociative recombination of h3 in the ground and excited Vibrational states
arXiv: Atomic Physics, 2007Co-Authors: Samantha Fonseca Dos Santos, Viatcheslav Kokoouline, Chris H GreeneAbstract:The article presents calculated dissociative recombination (DR) rate coefficients for H+3 . The previous theoretical work on H+3 was performed using the adiabatic hyperspherical approximation to calculate the target ion Vibrational states and it considered just a limited number of ionic rotational states. In this study, we use accurate Vibrational wave functions and a larger number of possible rotational states of the H3+ ground Vibrational Level. The DR rate coefficient obtained is found to agree better with the experimental data from storage-ring experiments than the previous theoretical calculation. We present evidence that excited rotational states could be playing an important role in those experiments for collision energies above 10 meV. The DR rate coefficients calculated separately for ortho- and para-H3+ are predicted to differ significantly at low energy, a result consistent with a recent experiment. We also present DR rate coefficients for Vibrationally-excited initial states of H3+, which are found to be somewhat larger than the rate coefficient for the ground Vibrational Level.
Barratt G Park - One of the best experts on this subject based on the ideXlab platform.
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photodissociation transition states characterized by chirped pulse millimeter wave spectroscopy
Proceedings of the National Academy of Sciences of the United States of America, 2020Co-Authors: Kirill Prozument, Joshua H Baraban, Bryan P Changala, Barratt G Park, Rachel G Shaver, J S MuenterAbstract:The 193-nm photolysis of CH2CHCN illustrates the capability of chirped-pulse Fourier transform millimeter-wave spectroscopy to characterize transition states. We investigate the HCN, HNC photofragments in highly excited Vibrational states using both frequency and intensity information. Measured relative intensities of J = 1–0 rotational transition lines yield Vibrational-Level population distributions (VPD). These VPDs encode the properties of the parent molecule transition state at which the fragment molecule was born. A Poisson distribution formalism, based on the generalized Franck–Condon principle, is proposed as a framework for extracting information about the transition-state structure from the observed VPD. We employ the isotopologue CH2CDCN to disentangle the unimolecular 3-center DCN elimination mechanism from other pathways to HCN. Our experimental results reveal a previously unknown transition state that we tentatively associate with the HCN eliminated via a secondary, bimolecular reaction.
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observation of b _2 symmetry Vibrational Levels of the so _2 tilde mbox c 1 b _2 state Vibrational Level staggering coriolis interactions and rotation vibration constants
arXiv: Chemical Physics, 2016Co-Authors: Barratt G Park, Jun Jiang, Catherine A Saladrigas, Robert W FieldAbstract:The $\mathrm{\tilde{C}}$ $^1$B$_2$ state of SO$_2$ has a double-minimum potential in the antisymmetric stretch coordinate, such that the minimum energy geometry has nonequivalent SO bond lengths. However, low-lying Levels with odd quanta of antisymmetric stretch (b$_2$ Vibrational symmetry) have not previously been observed because transitions into these Levels from the zero-point Level of the $\mathrm{\tilde{X}}$ state are vibronically forbidden. We use IR-UV double resonance to observe the b$_2$ Vibrational Levels of the $\mathrm{\tilde{C}}$ state below 1600 cm$^{-1}$ of Vibrational excitation. This enables a direct characterization of the Vibrational Level staggering that results from the double-minimum potential. In addition, it allows us to deperturb the strong $c$-axis Coriolis interactions between Levels of a$_1$ and b$_2$ Vibrational symmetry, and to determine accurately the Vibrational dependence of the rotational constants in the distorted $\mathrm{\tilde{C}}$ electronic state.
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observation of b2 symmetry Vibrational Levels of the so2 c 1 b2 state Vibrational Level staggering coriolis interactions and rotation vibration constants
Journal of Chemical Physics, 2016Co-Authors: Barratt G Park, Jun Jiang, Catherine A Saladrigas, Robert W FieldAbstract:The C (1)B2 state of SO2 has a double-minimum potential in the antisymmetric stretch coordinate, such that the minimum energy geometry has nonequivalent SO bond lengths. However, low-lying Levels with odd quanta of antisymmetric stretch (b2 Vibrational symmetry) have not previously been observed because transitions into these Levels from the zero-point Level of the X state are vibronically forbidden. We use IR-UV double resonance to observe the b2 Vibrational Levels of the C state below 1600 cm(-1) of Vibrational excitation. This enables a direct characterization of the Vibrational Level staggering that results from the double-minimum potential. In addition, it allows us to deperturb the strong c-axis Coriolis interactions between Levels of a1 and b2 Vibrational symmetry and to determine accurately the Vibrational dependence of the rotational constants in the distorted C electronic state.
Katharine L Reid - One of the best experts on this subject based on the ideXlab platform.
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comment on photoelectron angular distributions as a probe of alignment in a polyatomic molecule picosecond time and angle resolved photoelectron spectroscopy of s1 p difluorobenzene j chem phys 111 1438 1999
Journal of Chemical Physics, 2013Co-Authors: Jonathan Midgley, Julia A Davies, Katharine L ReidAbstract:In this Comment we submit the results of an experiment in which we use the technique of time-resolved photoelectron velocity map imaging to probe the intramolecular dynamics occurring following the preparation of the 3151 Vibrational Level in S1 p-difluorobenzene with a 1 ps laser pulse. The extracted photoelectron angular distributions are discussed in the context of earlier comparable measurements from our group [J. Chem. Phys. 111, 1438 (1999)], and we conclude that the specific interpretation of the earlier results was incorrect as a consequence of systematic errors that are removed in the present study.
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photoionization dynamics of ammonia b1e dependence on ionizing photon energy and initial Vibrational Level
Journal of Physical Chemistry A, 2010Co-Authors: Paul Hockett, Michael Staniforth, Katharine L ReidAbstract:In this article we present photoelectron spectra and angular distributions in which ion rotational states are resolved. This data enables the comparison of direct and threshold photoionization techniques. We also present angle-resolved photoelectron signals at different total energies, providing a method to scan the structure of the continuum in the near-threshold region. Finally, we have studied the influence of Vibrational excitation on the photoionization dynamics.
D C Moule - One of the best experts on this subject based on the ideXlab platform.
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variational study on the Vibrational Level structure and Vibrational Level mixing of highly Vibrationally excited s0 d2co
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2012Co-Authors: Svetoslav Rashev, D C Moule, Vladimir RashevAbstract:Abstract We perform converged high precision variational calculations to determine the frequencies of a large number of Vibrational Levels in S 0 D 2 CO, extending from low to very high excess Vibrational energies. For the calculations we use our specific Vibrational method (recently employed for studies on H 2 CO), consisting of a combination of a search/selection algorithm and a Lanczos iteration procedure. Using the same method we perform large scale converged calculations on the Vibrational Level spectral structure and fragmentation at selected highly excited overtone states, up to excess Vibrational energies of ∼17000 cm −1 , in order to study the characteristics of intramolecular Vibrational redistribution (IVR), Vibrational Level density and mode selectivity.
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variational study on the Vibrational Level structure and ivr behavior of highly Vibrationally excited s0 formaldehyde
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2012Co-Authors: Svetoslav Rashev, D C MouleAbstract:We perform large scale converged variational Vibrational calculations on S(0) formaldehyde up to very high excess Vibrational energies (E(v)), E(v)∼17,000cm(-1), using our Vibrational method, consisting of a specific search/selection/Lanczos iteration procedure. Using the same method we investigate the Vibrational Level structure and intramolecular Vibrational redistribution (IVR) characteristics for various Vibrational Levels in this energy range in order to assess the onset of IVR.
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calculations on the Vibrational Level density in highly excited formaldehyde
Chemical Physics, 2003Co-Authors: Svetoslav Rashev, D C MouleAbstract:Abstract The object of the present work is to develop a model that provides realistic estimates of the Vibrational Level density in polyatomic molecules in a given electronic state, at very high (chemically relevant) Vibrational excitation energies. For S 0 formaldehyde (D 2 CO), acetylene, and a number of triatomics, the estimates using conventional spectroscopic formulas have yielded densities at the dissociation threshold, very much lower than the experimentally measured values. In the present work we have derived a general formula for the Vibrational energy Levels of a polyatomic molecule, which is a generalization of the conventional Dunham spectroscopic expansion. Calculations were performed on the Vibrational Level density in S 0 D 2 CO, H 2 C 2 , and NO 2 at excitation energies in the vicinity of the dissociation limit, using the newly derived formula. The results from the calculations are in reasonable agreement with the experimentally measured data.
Svetoslav Rashev - One of the best experts on this subject based on the ideXlab platform.
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variational study on the Vibrational Level structure and Vibrational Level mixing of highly Vibrationally excited s0 d2co
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2012Co-Authors: Svetoslav Rashev, D C Moule, Vladimir RashevAbstract:Abstract We perform converged high precision variational calculations to determine the frequencies of a large number of Vibrational Levels in S 0 D 2 CO, extending from low to very high excess Vibrational energies. For the calculations we use our specific Vibrational method (recently employed for studies on H 2 CO), consisting of a combination of a search/selection algorithm and a Lanczos iteration procedure. Using the same method we perform large scale converged calculations on the Vibrational Level spectral structure and fragmentation at selected highly excited overtone states, up to excess Vibrational energies of ∼17000 cm −1 , in order to study the characteristics of intramolecular Vibrational redistribution (IVR), Vibrational Level density and mode selectivity.
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variational study on the Vibrational Level structure and ivr behavior of highly Vibrationally excited s0 formaldehyde
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2012Co-Authors: Svetoslav Rashev, D C MouleAbstract:We perform large scale converged variational Vibrational calculations on S(0) formaldehyde up to very high excess Vibrational energies (E(v)), E(v)∼17,000cm(-1), using our Vibrational method, consisting of a specific search/selection/Lanczos iteration procedure. Using the same method we investigate the Vibrational Level structure and intramolecular Vibrational redistribution (IVR) characteristics for various Vibrational Levels in this energy range in order to assess the onset of IVR.
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calculations on the Vibrational Level density in highly excited formaldehyde
Chemical Physics, 2003Co-Authors: Svetoslav Rashev, D C MouleAbstract:Abstract The object of the present work is to develop a model that provides realistic estimates of the Vibrational Level density in polyatomic molecules in a given electronic state, at very high (chemically relevant) Vibrational excitation energies. For S 0 formaldehyde (D 2 CO), acetylene, and a number of triatomics, the estimates using conventional spectroscopic formulas have yielded densities at the dissociation threshold, very much lower than the experimentally measured values. In the present work we have derived a general formula for the Vibrational energy Levels of a polyatomic molecule, which is a generalization of the conventional Dunham spectroscopic expansion. Calculations were performed on the Vibrational Level density in S 0 D 2 CO, H 2 C 2 , and NO 2 at excitation energies in the vicinity of the dissociation limit, using the newly derived formula. The results from the calculations are in reasonable agreement with the experimentally measured data.
