Browsing by Author "Teranishi, Y."

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A master equation approach to the dynamics of zero electron kinetic energy (ZEKE) states and ZEKE spectroscopy
(2011-02-14)
Wang, Yi-Hsieh
;
Mineo, H.
;
Chao, S. D.
;
Selzle, H. L.
;
Neusser, H. J.
We have theoretically studied important dynamic processes involved in zero electron kinetic energy (ZEKE) spectroscopy using the density matrix method with the inverse Born-Oppenheimer approximation basis sets. In ZEKE spectroscopy, the ZEKE Rydberg states are populated by laser excitation (either a one- or two- photon process), which is followed by autoionizations and l-mixing due to a stray field. The discrimination field is then applied to ionize loosely bound electrons in the ZEKE states. This is followed by using the extraction field to extract electrons from the ZEKE levels which have a strength comparable to that of the extraction field. These extracted electrons are measured for the relative intensities of the ion states under investigation. The spectral positions are determined by the applied laser wavelength and modified by the extraction electric field. In this paper, all of these processes are conducted within the context of the density matrix method. The density matrix method can provide not only the dynamics of system's population and coherence (or phase) but also the rate constants of the processes involved in the ZEKE spectroscopy. Numerical examples are given to demonstrate the theoretical treatments. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3547363]
Direct observation of super-excited states in methane created by a femtosecond intense laser field
(2008-11-28)
Azarm, A.
;
Xu, H. L.
;
Kamali, Y.
;
Bernhardt, J.
;
Song, D.
We report, for the first time, a direct observation of the super-excited states of CH(4) in femtosecond intense laser fields using a pump (800 nm)-probe (1338 nm) technique. An unambiguous depletion of the CH (A (2) Delta -> X (2)Pi) fluorescence signal as a function of the delay time is attributed to the de-excitation of the super-excited states by the probe laser pulse. The lifetime of the super-excited state is measured to be about 160 fs.
High-temperature ratchets driven by deterministic and stochastic fluctuations
(2019-01-03)
Rozenbaum, V. M.
;
Shapochkina, I. V.
;
Teranishi, Y.
;
Trakhtenberg, L. I.
;
物理研究所
We consider the overdamped dynamics of a Brownian particle in an arbitrary spatial periodic and time-dependent potential on the basis of an exact solution for the probability density in the form of a power series in the inverse friction coefficient. The expression for the average velocity of a Brownian ratchet is simplified in the high-temperature consideration when only the first terms of the series can be used. For the potential of an additive-multiplicative form (a sum of a time-independent contribution and a time-dependent multiplicative perturbation), general explicit expressions are obtained which allow comparative analysis of frequency dependencies of the average velocity, implying deterministic and stochastic potential energy fluctuations. For qualitative and quantitative analysis of these dependences, we choose illustrative examples for spatial harmonic fluctuations: with deterministic time dependences of a relaxation type and stochastic time dependences describing Markovian dichotomous and harmonic noise processes. We explore the influence of fluctuation types on the ratchet effect and demonstrate its enhancement in the case of harmonic noise.
Highly Multiphoton Excitation of Molecule by Intense Laser Field
(2009)
Teranishi, Y.
;
Hayashi, M.
;
Song, D.
;
Azarm, A.
;
Kong, F.
Multiphoton excitation of molecule by intense laser field is studied theoretically to explain the recent experiments of neutral fragmentation Neutral fragments are created from highly excited parent molecule Excitation mechanism is discussed with the use of Floqet theory.
Highly multiphoton molecular excitation by an intense laser pulse
(2008)
Teranishi, Y.
;
Hayashi, M.
;
Kong, F.
;
Chin, S. L.
;
Chao, S. D.
Multiphoton excitation of molecules by an intense laser field is treated. When the first excitation energy is much larger than both the photon energy and the transition energy between excited states, excited states are strongly coupled with each other by the photon, even though coupling with the ground state is weak. In such a case, a kind of collective excitation takes places, in which the excitation probability of every excited state is almost linear as functions of intensity on a log-log plot, and the slope is independent of the final state. By taking methane and formaldehyde as examples we numerically study this process.
Molecular ionization of cyclohexanone in femtosecond laser fields: An application of ADK theory
(2009-08-01)
Wang, Q. Q.
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Mineo, H.
;
Wu, D.
;
Jin, M. X.
;
Chin, C. H.
The mechanisms of ionization and dissociation of cyclohexanone (C(6)H(10)O) in a 90 fs, 788 nm linearly polarized laser field ranging from 10(13) to 10(14) W/cm(2) by a time-of-flight mass spectrometer (TOF-MS) have been investigated. The ion yields as a function of laser intensity have been measured experimentally. By comparison with the Ammosov-Delone-Krainov (ADK) theory based on a hydrogen-like model, the ionization mechanism of cyclohexanone in this intense femtosecond laser field has been understood. Considering the importance of molecular nuclear motions, we propose that the Franck-Condon (F-C) factor can provide the excess vibrational energy in the molecular ion. This energy is required for the decomposition of the molecular ion which finally results in the observed mass spectrum.
Neutral dissociation of hydrogen molecules in a strong laser field through superexcited states
(2011-04-28)
Azarm, A.
;
Song, D.
;
Liu, K.
;
Hosseini, S.
;
Teranishi, Y.
Fragmentation of hydrogen molecules in a strong laser field is studied experimentally and theoretically. Balmer lines (n -> 2) from hydrogen atoms are observed up to n = 14. The emission intensity of the two strongest Balmer lines versus laser intensity in a log-log plot gives a slope of more than 11. This indicates that some high-lying states in the continuum are excited resulting in neutral dissociation. Adapting Rydberg state approximation, the potential energy curves of superexcited states of hydrogen are plotted. Semi-empirical calculation confirms dissociation through these superexcited states. The upper limit of the lifetime of the superexcited states is obtained by an ultrafast pump and probe experiment by monitoring one of the fluorescence lines.
Neutral dissociation of simple molecules in strong laser field
(2011)
Azarm, A.
;
Song, D.
;
Teranishi, Y.
;
Hosseini, S.
;
Lin, S. H.
we report neutral dissociation of simple molecules in strong laser field, experimentally. Moreover, theoretical calculations of potential energy curves justify neutral dissociation through super excited states in all of the investigated gases. (C) 2010 Optical society of America
Population trapping and rotational revival of N(2) molecules during filamentation of a femtosecond laser pulse in air
(2010-12-14)
Azarm, A.
;
Ramakrishna, S.
;
Talebpour, A.
;
Hosseini, S.
;
Teranishi, Y.
We study the fluorescence emitted from filaments in air using a pump-probe scheme with a femtosecond Ti-sapphire laser. The fluorescence intensities from the first negative band (B(2)Sigma(+)(u) -> X(2)Sigma(+)(g)) and the second positive band (C(3)Pi(u) -> B(3)Pi(g)) show enhancement and change periodically as a function of the pump-probe time delay. We attribute this phenomenon to the universal yet probably forgotten phenomenon of population trapping of nitrogen molecules in highly excited states together with field-induced alignment of nitrogen molecules followed by revivals of the rotational wavepackets. Theoretical calculation of the alignment dynamics of nitrogen molecules is consistent with the experimental data.
Population trapping and rotational revival of N-2 molecules during filamentation of a femtosecond laser pulse in air
(2010-12-14)
Azarm, A.
;
Ramakrishna, S.
;
Talebpour, A.
;
Hosseini, S.
;
Teranishi, Y.
We study the fluorescence emitted from filaments in air using a pump-probe scheme with a femtosecond Ti-sapphire laser. The fluorescence intensities from the first negative band (B-2 Sigma(+)(u) -> X-2 Sigma(+)(g)) and the second positive band (C-3 Pi(u) -> B-3 Pi(g)) show enhancement and change periodically as a function of the pump-probe time delay. We attribute this phenomenon to the universal yet probably forgotten phenomenon of population trapping of nitrogen molecules in highly excited states together with field-induced alignment of nitrogen molecules followed by revivals of the rotational wavepackets. Theoretical calculation of the alignment dynamics of nitrogen molecules is consistent with the experimental data.
Studying the neutral dissociation of O-2 and CH4 Molecules in strong laser field
(2009)
Azarm, A.
;
Kamali, Y.
;
Bernhardt, J.
;
Xu, H. L.
;
Song, D.
We report neutral dissociation of oxygen and methane in femtosecond laser field through superexcited states. Moreover, the lifetime of the superexcited state is measured by pump and probe technique to be about few hundred femtosecond. (C)2009 Optical Society of America
Symmetry of deterministic ratchets
(2019-08-13)
Rozenbaum, V. M.
;
Shapochkina, I., V
;
Teranishi, Y.
;
Trakhtenberg, L., I
;
物理研究所
We consider the overdamped motion of a Brownian particle in an unbiased force field described by a periodic function of coordinate and time. A compact analytical representation has been obtained for the average particle velocity as a series in the inverse friction coefficient, from which follows a simple and clear proof of hidden symmetries of ratchets, reflecting the symmetry of summation indices of the applied force harmonics relative to their numbering from left to right and from right to left. We revealed the conditions under which (i) the ratchet effect is absent; (ii) the ratchet average velocity is an even or odd functional of the applied force, whose dependences on spatial and temporal variables are characterized by periodic functions of the main types of symmetries: shift, symmetric, and antisymmetric, and universal, which combines all three types. These conditions have been specified for forces with those dependences of a multiplicative (or additive-multiplicative) and additive structure describing two main ratchet types, pulsating and forced ratchets. We found the fundamental difference in dependences of the average velocity of pulsating and forced ratchets on parameters of spatial and temporal asymmetry of potential energy of a particle for systems in which the spatial and temporal dependence is described by a sawtooth potential and a deterministic dichotomous process, respectively. In particular, it is shown that a pulsating ratchet with a multiplicative structure of its potential energy cannot move directionally if the energy is of the universal symmetry type in time; this restriction is removed in the inertial regime, but only if the coordinate dependence of the energy does not belong to either symmetric or antisymmetric functions.
Symmetry of Pulsating Ratchets
(2018-04-01)
Rozenbaum, V. M.
;
Shapochkina, I. V.
;
Teranishi, Y.
;
Trakhtenberg, L. I.
;
物理研究所
Using an exact expression for the average velocity of inertialess motion of pulsating ratchets, a simple proof is given for the recently discovered hidden space-time symmetry of Cubero-Renzoni (D. Cubero, F. Renzoni, 2016). The conditions are revealed for the absence of the ratchet effect in systems with potential energies described by products of periodic functions of coordinate and time possessing the symmetry of the main types. In particular, it is shown that the ratchet effect is absent for the time dependence of the universal symmetry type (which combines three standard symmetries), and this restriction is removed when inertia is taken into account, unless the coordinate dependence of the potential energy is related to symmetric or antisymmetric functions.
Theoretical and Experimental Investigations of Ionization-Dissociation of Polyatomic Molecules
(2009)
Wang, Qiaoqiao
;
Jin, Mingxing
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Ding, Dajun
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Mineo, H.
;
Chao, S. D.
The Keldysh theory originally developed for the ionization of Is state of hydrogen atom has been generalized for molecules by introducing the molecular orbital theory and the Born-Oppenheimer approximation. Ionization and dissociation mechanisms of cyclopentanone in the intense 800 nm laser field (10(13) to 10(14) W/cm(2)) have been experimentally investigated by using a method of molecular beam and time-of-flight mass spectrometer (TOF-MS). Singly-charged parent ion and numerous fragment ions are observed in the mass spectra, which are analyzed by using the molecular Keldysh theory.
Theoretical studies of ZEKE spectroscopy and dynamics of high Rydberg states
(2010-02-12)
Wang, Yi-Hsieh
;
Teranishi, Y.
;
Mineo, H.
;
Chao, S. D.
;
Selzle, H. L.
A main purpose of this Letter is to show how to employ the inverse Born-Oppenheimer approximation as a basis set to study zero kinetic energy (ZEKE) spectroscopy and the autoionization dynamics of the ZEKE states. The calculations of channel couplings, quantum defects, intensity borrowing, vibrational and rotational autotionizations will be demonstrated by using a homonuclear diatomic molecule as an example. (C) 2010 Elsevier B. V. All rights reserved.
Ultrafast electronic motion in hydrogen molecular ions induced by a high power intense laser
(2010-10-20)
Mineo, H.
;
Teranishi, Y.
;
Chao, S. D.
;
Lin, S. H.
;
應用化學系分子科學碩博班
In this Letter we report a method for controlling electronic localization in a molecular ion, on an attosecond time scale, using a high-intensity laser, based on two different excitation mechanisms. One takes place during ionization, and the other takes place sequentially, following ionization. The electronic excited states of the hydrogen molecular ion are created during ionization by taking the configuration interaction mixing of neutral molecules into account. We detect the ultrafast oscillatory electronic motion between two atoms in a hydrogen molecular ion occurring due to the creation of excited states during the course of ionization. (c) 2010 Elsevier B.V. All rights reserved.
Ultrafast electronic motion in hydrogen molecular ions induced by a high power intense laser
(2010-10-20)
Mineo, H.
;
Teranishi, Y.
;
Chao, S. D.
;
Lin, S. H.
;
應用化學系
In this Letter we report a method for controlling electronic localization in a molecular ion, on an attosecond time scale, using a high-intensity laser, based on two different excitation mechanisms. One takes place during ionization, and the other takes place sequentially, following ionization. The electronic excited states of the hydrogen molecular ion are created during ionization by taking the configuration interaction mixing of neutral molecules into account. We detect the ultrafast oscillatory electronic motion between two atoms in a hydrogen molecular ion occurring due to the creation of excited states during the course of ionization. (c) 2010 Elsevier B.V. All rights reserved.