第159回

Recent advances in laser technology have provided methods to track the dynamics of the electrons in molecular systems. The molecular systems in intense laser-field involves repetitive re-collision of the ionizing electron and parent ion and intense emission of radiation, thus resulting in high-order harmonic generation (HHG) and above-threshold ionization (ATI) processes. Moreover, the availability of intense X-ray laser pulse allows further investigations involving auto-ionization and the Auger effect. The theoretical studies of HHG processes and ATI processes have succeeded in giving reasonably accurate results for a single atomic system or very small molecules. In this talk, I would introduce my theoretical studies on nonadiabatic electron dynamics of molecules in intense laser field. Time-dependent configuration interaction method has been applied to single water molecule system with nuclear nonadiabatic effect. The electron wavefunction is represented by complex natural orbitals, thus allowing evaluation of electron flux, which is an one-particle operator, for each natural orbitals. Within this treatment, we can determine how the nuclear nonadiabatic force induce the electron flux and clarify the validity of adiabatic approximation. Ionization process has been included in the calculations by means of continuity equations of electron fluxes for each complex natural orbital, which allows us to target molecular system in intense laser field. The nuclear nonadiabatic effect introduces isotope effect in ATI process and HHG process for systems in intense laser field. The path-branching method has also been implemented, thereby the symmetry-breaking force induced by nuclear nonadiabatic effect introduces spontaneous symmetry-breaking to the electronic state. System of single water molecule in intense laser field undergoes electronic excitation to continuum state. The symmetry-breaking induced by nuclear nonadiabatic effect for such system can be attributed to pseudo-Jahn-Teller effect. The numerical calculation allows a simple evaluation of complex nuclear nonadiabatic effect among quasi-degenerate electronic states.