Prof. Shih-I Chu

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Atomic and Molecular Physics in Strong Fields

Wavelet time-frequency spectrum for H₂ molecules in intense laser fields
The study of the structure and dynamics of atoms and molecules in the presence of intense external fields is a subject of contemporary importance in science and technology. In particular, the advancement of intense ultrashort laser pulse technology has led to the discovery of a number of novel and very high-order (100th to 300th order) multi-photon and nonlinear optical phenomena that cannot be treated by means of traditional perturbation theories.

In the last two decades, Professor Chu and his group have undertaken a series of pioneering developments of non-perturbative time-independent generalized Floquet formalisms and complex quasi-energy methods as well as various large-scale time-dependent methods for accurate and comprehensive ab initio investigation of a broad range of atomic and molecular multiphoton processes and phenomena in intense and super-intense laser fields. Among the strong-field processes being studied are: multiphoton and above-threshold ionization of atoms, multiphoton and above-threshold dissociation of molecules, the nature of chemical bonds in intense laser fields (bond softening and hardening), Coulomb explosion, very-high-order harmonic generation and table-top x-ray laser, comb laser, and more recently, attosecond science and technology, etc.

Today, the generalized Floquet Formalism is one of the two most widely used frameworks in strong-field atomic, molecular, and optical (AMO) physics research. Publications listed in "Volume 2" are devoted entirely to the generalized Floquet developments and their applications, and "Volume 3" is concerned with the development of new time-dependent (quantum, classical, and semi-classical) methods to atomic and molecular processes in strong fields.

Representative Publications:

S. I. Chu and W. P. Reinhardt, Intense field multiphoton ionization via complex dressed states: Application to the H atom, Phys. Rev. Lett. 39, 1195–1198 (1977) [BibTeX] [link] [pdf]
S. I. Chu, Recent developments in semiclassical Floquet theories for intense-field multiphoton processes in Advances in Atomic and Molecular Physics (Academic Press, New York, 1985), vol. 21, pp. 197–253 [BibTeX]
S. I. Chu, Generalized Floquet theoretical approaches to multiphoton and nonlinear optical processes in intense laser fields in Advances in Chemical Physics (John Wiley & Sons, New York, 1989), vol. 73, pp. 739–799 [BibTeX] [link]
S. I. Chu, Z. C. Wu, and E. Layton, Density matrix formulation of complex geometric quantum phases in dissipative systems, Chem. Phys. Lett. 157, 151–158 (1989) [BibTeX] [link] [pdf]
G. H. Yao and S. I. Chu, Laser-induced molecular stabilization and trapping and chemical bond hardening in intense laser fields, Chem. Phys. Lett. 197, 413–418 (1992) [BibTeX] [link] [pdf]
X. M. Tong and S. I. Chu, Theoretical study of multiple high-order harmonic generation by intense ultrashort pulsed laser fields: A new generalized pseudospectral time-dependent method, Chem. Phys. 217, 119–130 (1997) [BibTeX] [link] [pdf]
D. A. Telnov and S. I. Chu, Floquet formulation of time-dependent density functional theory, Chem. Phys. Lett. 264, 466–476 (1997) [BibTeX] [link] [pdf]
X. M. Tong and S. I. Chu, Generation of circularly polarized multiple high-order harmonic emission from two-color crossed laser beams, Phys. Rev. A 58, R2656–R2659 (1998) [BibTeX] [link] [pdf]
X. M. Tong and S. I. Chu, Probing the spectral and temporal structures of high-order harmonic generation in intense laser pulses, Phys. Rev. A 61, 021802(R) (2000) [BibTeX] [link] [pdf]
K. T. Chung and S. I. Chu, Two-photon detachment of H^-, Phys. Rev. A 61, 060702(R) (2000) [BibTeX] [link] [pdf]
X. Chu and S. I. Chu, Complex-scaling generalized pseudospectral method for quasienergy resonance states in two-center systems: Application to the Floquet study of charge resonance enhanced multiphoton ionization of molecular ions in intense low-frequency laser fields, Phys. Rev. A 63, 013414 (2001) [BibTeX] [link] [pdf]
X. Chu and S. I. Chu, Self-interaction-free time-dependent density-functional theory for molecular processes in strong fields: High-order harmonic generation of H₂ in intense laser fields, Phys. Rev. A 63, 023411 (2001) [BibTeX] [link] [pdf]
D. A. Telnov and S. I. Chu, Multiphoton above-threshold detachment of Li^-: Exterior-complex-scaling-generalized-pseudospectral method for calculations of complex-quasienergy resonances in Floquet formulation of time-dependent density-functional theory, Phys. Rev. A 66, 043417 (2002) [BibTeX] [link] [pdf]
X. Chu and S. I. Chu, Role of the electronic structure and multielectron responses in ionization mechanisms of diatomic molecules in intense short-pulse lasers: An all-electron ab initio study, Phys. Rev. A 70, 061402(R) (2004) [BibTeX] [link] [pdf]
D. A. Telnov and S. I. Chu, High-order above-threshold multiphoton detachment of H^-: time-dependent non-Hermitian Floquet approach, J. Phys. B: At. Mol. Opt. Phys. 37, 1489–1502 (2004) [BibTeX] [link] [pdf]
D. A. Telnov and S. I. Chu, Ab initio study of high-order harmonic generation of H₂⁺ in intense laser fields: Time-dependent non-Hermitian Floquet approach, Phys. Rev. A 71, 013408 (2005) [BibTeX] [link] [pdf]
Z. Y. Zhou and S. I. Chu, Exploration of Coulomb explosion dynamics through excited vibrational states of molecule, Phys. Rev. A 71, 011402(R) (2005) [BibTeX] [link] [pdf]
X. Guan, X. M. Tong, and S. I. Chu, Effect of electron correlation on high-order-harmonic generation of helium atoms in intense laser fields: Time-dependent generalized pseudospectral approach in hyperspherical coordinates, Phys. Rev. A 73, 023403 (2006) [BibTeX] [link] [pdf]

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Dept. of Chemistry
The University of Kansas