Browsing by Author "CHU, SI"

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HIGH-ORDER HARMONIC-GENERATION IN ATOMIC-HYDROGEN AT 248-NM - DIPOLE-MOMENT VERSUS ACCELERATION SPECTRUM
(1992-12-01)
JIANG, TF
;
CHU, SI
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電子物理學系
;
Department of Electrophysics
We present a study of the high-order harmonic-generation (HG) spectra of atomic hydrogen at 248 nm based on the Fourier transform of the expectation values of the induced dipole moment and acceleration. The calculations were performed by extending a fast-Fourier-transformation split-operator technique (in spherical coordinates) to the solution of the time-dependent wave functions in intense laser fields. It is seen that the acceleration form provides a more satisfactory and accurate framework for the study of the photoemission HG spectrum at very intense fields, particularly when ionization becomes appreciable.
NONPERTURBATIVE METHODS FOR THE STUDY OF MULTIPHOTON DYNAMICS IN INTENSE PERIODIC AND MULTICOLOR LASER FIELDS
(1991-02-01)
CHU, SI
;
JIANG, TF
;
電子物理學系
;
Department of Electrophysics
We present a brief account of some recently developed generalized Floquet methods (both time-dependent and time-independent) for the nonperturbative treatment of the time-development of wavefunctions or the density matrix operator of quantum systems driven by intense periodic or multi-color (multi-frequency) laser fields. Both the Schrodinger and Liouville equations are considered. We also explore the feasibility of the fast Fourier transformation (FFT) propagation method for the study of Rydberg atom dynamics. We then present a FFT case study of the time propagation of the wavefunction and coarse-grained Wigner density distribution for the problem of microwave-driven multiphoton excitation and ionization of Rydberg hydrogen atoms.
TIME EVOLUTION AND MULTIPHOTON IONIZATION OF RYDBERG WAVEPACKET IN MICROWAVE FIELDS
(1995-06-30)
JIANG, TF
;
CHU, SI
;
物理研究所
;
Institute of Physics
We present a theoretical study of the time evolution of Rydberg wavepacket, initially localized in radial space and mimicking the classical particle, undergoing microwave multiphoton ionization. The dynamical behavior of the Rydberg wavepacket is found to be different from that of Rydberg atoms initially prepared at given Rydberg eigenstates. It is seen that the Rydberg wavepacket can exhibit collapse and revival behavior in the short time regime. Further, both the microwave ionization rates and the quantum phase space trajectories of the Rydberg wavepackets exhibit qualitatively different behavior in small scaled-frequency (omega(s) (=omega n(0)(3)) << 1.0) and large scaled-frequency (omega(s) greater than or equal to 1.0) regimes.