Time-Dependent Unitary Transformation Method in the Strong-Field-Ionization Regime with the Kramers-Henneberger Picture

International Journal of Molecular Sciences

Dong-Eon Kim¹  Je-Hoi Mun¹  Hirofumi Sakai² 

[1] Department of Physics and Center for Attosecond Science and Technology, POSTECH, Pohang 37673, Korea;Department of Physics, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan;

关键词: numerical method;    laser-matter interaction;    time-dependent Schrödinger equation;    time-dependent unitary transformation method;    strong-field ionization;    Kramers-Henneberger frame;   

DOI  :  10.3390/ijms22168514

来源: DOAJ

【 摘 要 】

Time evolution operators of a strongly ionizing medium are calculated by a time-dependent unitary transformation (TDUT) method. The TDUT method has been employed in a quantum mechanical system composed of discrete states. This method is especially helpful for solving molecular rotational dynamics in quasi-adiabatic regimes because the strict unitary nature of the propagation operator allows us to set the temporal step size to large; a tight limitation on the temporal step size ($\delta t<<1$) can be circumvented by the strict unitary nature. On the other hand, in a strongly ionizing system where the Hamiltonian is not Hermitian, the same approach cannot be directly applied because it is demanding to define a set of field-dressed eigenstates. In this study, the TDUT method was applied to the ionizing regime using the Kramers-Henneberger frame, in which the strong-field-dressed discrete eigenstates are given by the field-free discrete eigenstates in a moving frame. Although the present work verifies the method for a one-dimensional atom as a prototype, the method can be applied to three-dimensional atoms, and molecules exposed to strong laser fields.

【 授权许可】

Unknown