Browsing by Author "Jiang, TF"

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Adomian's decomposition method for eigenvalue problems
(2005-03-01)
Kao, YM
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Jiang, TF
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應用數學系
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物理研究所
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Department of Applied Mathematics
We extend the Adomian's decomposition method to work for the general eigenvalue problems, in addition to the existing applications of the method to boundary and initial value problems with nonlinearity. We develop the Hamiltonian inverse iteration method which will provide the ground state eigenvalue and the explicit form eigenfunction within a few iterations. The method for finding the excited states is also proposed. We present a space partition method for the case that the usual way of series expansion failed to converge.
Adomian's decomposition method for electromagnetically induced transparency
(2005-12-01)
Kao, YM
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Jiang, TF
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Yu, IA
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應用數學系
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物理研究所
We developed the Adomian's decomposition method to work for the electromagnetically induced transparency (EIT) problem. The method is general and capable to solve the coupled nonlinear partial differential equations for a light pulse passing through a three-level Lambda-type coherent medium. This EIT system is described by the coupled Maxwell-Schrodinger equations and optical Bloch equations. In the weak probe field case, the results agree with perturbation solutions and experimental data. In the stronger probe field case while perturbation may fail, our results reproduce experimental data well. With the techniques of spatial and time partitions, we extend the decomposition method that will be versatile for the investigation of the light pulse propagating through a coherent atomic medium.
Cantori barriers in the excitation of a diatomic molecule by chirped pulses
(1999-08-28)
Lin, JT
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Jiang, TF
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物理研究所
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Institute of Physics
We present a nonlinear dynamical study of a diatomic molecule under the interaction of chirped pulses. The step-like dissociation probability with respect to the initial vibrational states reflects the cantori barriers during the excitation process. The correspondence between classical and quantum cantori barriers is shown through classical phase trajectory and quantum Husimi distribution function. According to the results, the quantum suppression of classical dissociation in molecular excitation by chirped pulse disappears at some field parameters.
Coulomb trajectory effects on electron-impact detachment of negative ions and on mutual neutralization cross sections
(1996-12-28)
Lin, JT
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Jiang, TF
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Lin, CD
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電子物理學系
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物理研究所
Cross sections of electron-impact detachment of negative ions and of mutual neutralization between positive and negative ions are calculated using a model based on the semiclassical theory for ion-atom collisions but modified to include Coulomb trajectory effects. It is shown that the method allows us to obtain accurate results for collisions down to low energies. The Coulomb repulsion between the electron and the negative ion accounts for the rapid decrease of detachment cross sections at low energies, and the Coulomb attraction between positive and negative ions accounts for the rapid increase of neutralization cross sections at low velocities.
Diatomic molecule under pulsed field: One-dimensional versus full-dimensional studies
(1998-09-01)
Lin, JT
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Chuu, DS
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Jiang, TF
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電子物理學系
;
物理研究所
This work investigates the dissociation dynamics of a diatomic molecule under the chirped pulse with the vibrational and rotational degrees of freedom. Results obtained herein are also compared with those of the conventionally used one-dimensional (ID) model. According to the comparison, the 1D model still provides valuable information such as dissociation dynamics. Meanwhile, predictions such as harmonic generation spectrum from the 1D model are impractical.
Direct momentum-space calculations for the resonant multiphoton processes of a hydrogen atom under intense laser pulses
(1996-01-01)
Pen, UL
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Jiang, TF
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物理研究所
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Institute of Physics
We present a momentum-space solution for the time-dependent Schrodinger equation of a realistic hydrogen atom in a strong laser pulse. The method can integrate the nonperturbative system to thousands of optical cycles, previously thought not yet feasible. A hydrogen atom under a 285-nm (4.357-eV), 97.5-TW/cm(2) short pulse is found to produce two prominent photoelectron peaks above threshold, and significant intermediate bound-state resonance with the 4p state. With a 248-nm (5-eV) probe laser pulse that is ten times longer, the resonant structure is explored.
Dissociation and dynamics of the high-vibrational-state HF molecules under intense half-cycle and few-cycle pulses
(2000-03-01)
Lin, JT
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Lin, SH
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Jiang, TF
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物理研究所
;
Institute of Physics
This work explores the dissociation dynamics and angular distribution of the HF molecule interacting with intense half-cycle and few-cycle pulses, including the rotational degree of freedom. The dependences of the dissociation probability on both the pulse type and the pulse duration are discussed. Our results indicate that the angular distribution of the dissociation probability is highly asymmetric to the perpendicular direction of field polarization, and becomes more symmetric with an increase in the number of field cycles. The spatial distribution of the wave function demonstrates the feasibility of constructing a molecular wave packer by interacting with the half-cycle pulse.
Electron detachment of H- in collision with Ne4+ and Ar4+ ions
(1997-09-01)
Lin, JT
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Jiang, TF
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Kuang, JY
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Lin, CD
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電子物理學系
Total-electron detachment cross sections for H- colliding with multiply charged Ne4+ and Ar4+ ions are calculated using the two-center atomic-orbital close-coupling expansion method in the center-of-mass energy range of 4-200 keV. The calculation shows that there is no core effect, and that electron capture only plays a minor role for energies above 20 keV. At 50 keV, where electron capture is not important, the single-center atomic-orbital expansion method was used to calculate the detachment cross sections for incident charges q=1-8. The present calculations are shown to be in good agreement with experimental data.
Excitation of the NO molecule by chirped infrared laser pulses
(1999-11-01)
Lin, JT
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Hayashi, M
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Lin, SH
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Jiang, TF
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物理研究所
To explore the insights of recent experiments on the excitation of the NO molecule by chirped subpicosecond IR pulses, a corresponding theoretical study is presented. The agreements between experimental and theoretical results show the importance of the full-dimensional quantum-mechanical calculation. [S1050-2947(99)04711-3].
Ionization of oriented elliptic Rydberg states by half-cycle pulses
(1997-03-01)
Jiang, TF
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Lin, CD
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物理研究所
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Institute of Physics
We calculate the ionization of elliptic Rydberg states by half-cycle unipolar electromagnetic-field pulses and examine the dependence of ionization probabilities on the eccentricity and the orientation of the ellipse with respect to the field direction of the pulse. It is suggested that the predicted large geometrical dependences be tested experimentally.
Ionization of the surface-state electron by half-cycle electric-field pulses
(1997-02-15)
Jiang, TF
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物理研究所
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Institute of Physics
The purpose of this research is to study the half-cycle pulse (HCP) ionization behavior of the surface-state electron (SSE). Motivated by the experimental progress in the HCP source, we propose to investigate the HCP excitation of the SSE system, which was confirmed to be one dimensional in nature. We examine the cases with a wide range of scaled electric-field amplitudes, which have different time scales and pulse shapes. Our results show some stabilization windows for the ionization probability with respect to these fields. The number of windows increases with the length of the pulse duration. The origin of the window is shown to be related to the energy gained from the driving electric fields.
Photodissociation of H-2(+) in intense chirped laser fields
(2001-01-01)
Lin, JT
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Jiang, TF
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物理研究所
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Institute of Physics
Regarding an experimental measurement of proton kinetic energy spectra of H-2(+) with a chirped pulse [L. J. Frasinski, J. H. Posthumus, J. Plumridge, and K. Golding, Phys. Rev. Lett. 83, 3625 (1999)], we present a nonperturbative, time-dependent calculation for the photodissociation of H-2(+) in intense laser fields by combining three numerical techniques. The results show a finer kinetic-energy distribution structure of a proton due to the intrapulse pump-dump mechanism between two electronic states as the pulse duration and intensity change. Higher-energy peaks are also suppressed by frequency chirping of the laser field. The dissociation probabilities show that a positively chirped pulse is always more efficient for population inversion than no chirping or negatively chirped pulses, and a slight coordinate shift of the initial state could result in a significant increase of dissociation probability.
Quantum dynamics of a diatomic molecule under chirped laser pulses
(1998-02-28)
Lin, JT
;
Lai, TL
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Chuu, DS
;
Jiang, TF
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電子物理學系
The photodissociation probability of a diatomic molecule is usually very small even under a strong field due to its anharmonicity. However, the progress in laser technology provides a chirped laser pulse to lower the threshold of the dissociation intensity. We investigate the quantum dynamics of a diatomic molecule under such a kind of pulse. It is found that there is a significant dissociation probability at moderate intensity for a diatomic molecule under a chirped pulse. The quantum dissociation probability is found to be suppressed with respect to the classical one for intensities above the dissociation threshold. Therefore the chirped pulse can efficiently dissociate a diatomic molecule.
The dependence of initial states on the excitation of NO molecules by chirped infrared laser pulses
(2000-08-28)
Lin, JT
;
Jiang, TF
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物理研究所
;
Institute of Physics
We study the effect of initial states on the chirping excitation of NO molecules in order to interpret recent experimental data. The results show that excitation is efficient when the probability density localizes along the polarization direction of the external field. Therefore, the thermal effect on the density distribution must be taken into account for the experimental case of 15 K. Furthermore, as the adiabatic limit is fully satisfied, the interference pattern of excited state populations disappears. This becomes a limiting factor under experimental conditions. We also find that excitation can be enhanced significantly when the pulse intensity is increased to fit the adiabatic criterion.
The phase of a bose-einstein condensate by the interference of matter waves
(2005-10-01)
Kuan, WH
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Jiang, TF
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物理研究所
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Institute of Physics
We present a calculation which produces the additional phase of a matter wave by applying an adiabatically changing optical field to a double-well Bose-Einstein condensate. An examination of the additional quantum phase is proposed through the comparison of the free expansion interference patterns of the perturbed double-well condensate and the pure double-well condensate.
Transition temperature of a weakly interacting Bose gas
(2006-04-01)
Kao, YM
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Jiang, TF
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物理研究所
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Institute of Physics
We report a theoretical study of the transition temperature of a trapped interacting dilute Bose gas. The system is treated like a two-fluid model consisting of a thermal component and a condensate component. Through the calculation of the energy spectra, the origins of various effects on the transition temperature are derived. We found that the interactive shift is affected by both the thermal component and the condensate component. The latter effect, which is about 34% of the former, has never been reported so far. With these two effects, our calculated interactive shift agrees very well with the recent measurement.
Two interacting electrons in a vertical quantum dot with magnetic fields
(2001-11-15)
Lin, JT
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Jiang, TF
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物理研究所
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Institute of Physics
We present a numerical exact calculation for the energy spectra of two electrons in a finite height cylindrical quantum dot in details by a coupled-channel method. The electron correlation energy for various geometry of quantum dots, with and without applied magnetic fields, for singlet and triplet states a-re investigated. The magnitude of magnetic field for transition of the spin-singlet ground state and the spin-triplet excited state is compared with experimental result. The study shows significant contributions due to the spreading of electron density distribution along the vertical direction. In contrast to the planar circular disk model, the study will be useful for some realistic quantum dots.