This proposal addresses comprehensive theoretical investigation of a broad range of atomic, molecular, and optical (AMO) processes of current significance in science and technology. The proposed activities will build on both of our past efforts and the new development of nonperturbative theoretical formalisms and high-precision computational methods for accurate treatment of both the electronic structure of highly and multiply excited states as well as the multiphoton dynamics and coherent control of atomic and molecular processes in the presence of intense external fields. Emphasis in the first part of this proposal concerns the ab initio theoretical exploration of the frequency comb structure and coherence within each order of the high-order harmonic generation (HHG) spectrum in the high-frequency VUV/XUV regime. Two approaches will be developed for the study of frequency comb projects: (a) time-dependent generalized pseudospectral method (TDGPS) for accurate and efficient solution of the time-dependent Schrdinger equation (TDSE) in space and time, and (b) many-mode Floquet theory (MMFT). The second part of this proposal will deal with the study of the coherent control of population transfer in Rydberg atoms via sequential transitions or via multiphoton adiabatic rapid passage. In the last part of the proposal, several longer range projects will be presented, including (a) the development of a new TDGPS method in hyperspherical coordinates for fully ab initio 6D treatment of doubly excited resonance states and double photoionization dynamics of two-electron atoms in the presence of external fields, and (b) the further development of the self-interaction-free time-dependent density functional theory (TDDFT) for the exploration of many-electron Rydberg atom dynamics.
This NSF project was focused on the development of new theoretical formalisms and large scale computational methods for the accurate and efficient treatment of novel atomic, molecular, and optical (AMO) physics phenomena of current interest in science and technology. The research has contributed to the fundamental understanding of the very-high-order nonlinear interaction of atomic and diatomic molecular systems as well as Rydberg atoms with intense laser or microwave fields. More specifically, we have performed the following several ab initio precision theoretical investigations: (a) Exploration of the frequency comb structure and coherence within each order of the high-order harmonic generation (HHG) spectrum in the high-frequency VUV/XUV regime; (b) Generalized Floquet treatment of the coherent control and enhancement of multiphoton processes driven by the frequency comb lasers; (c) Development of time-dependent generalized pseudospectral (TDGPS) method in hyperspherical coordinate system (HSC) for accurate and efficient 6D treatment of high-lying doubly excited resonance states of two-electron atoms in the presence of external fields, (d) Exploration of the delicate effect of electron correlation on the HHG spectra of two-electron atoms in intense ultrashort laser pulses, etc. The students trained under this project are well prepared for performing frontier AMO physics research as well as multidisciplinary research on topics of current technological importance.
