Photoionization Dynamics In Time Domain

The interaction between laser and matter is one of the most common and basic phys-ical processes.With the rapid development of femtosecond laser,the study of strong field physics makes it possible to observe the movement of microscopic particles on the attosec-ond time scale.In order to better explain the phenomena observed in the experiments and explore the most essential physical process of the interaction between light and matter,many theoretical models for calculating photoionization of atoms have emerged.In this paper,the R-matrix method is used to study the atomic structure of neutral F and Ne atoms.And the R-matrix method is also used to calculate the time delays of different shell electron ionization processes.The paper is mainly divided into two parts.Firstly,the near threshold structure of photoionization of F atoms is studied.Because the atomic number of F atom is small,the non-relativistic R-matrix method theory can obtain a good agreement with the experimental results.To construct the F~+ion wave function,we consider the effect of channel coupling and core-valence interaction.Then we present the first fourteen energy levels of F~+states.In the energy range of 17eV-22.5eV,the photoionization cross sections of F atoms are given.The interactions between Rydberg series and individual resonances are analyzed.Secondly,the wave functions and photoionization cross sections of Ne atoms are calculated.Configuration interaction and core-valence interaction are also considered in constructing the wave function.The calculated energy levels of Ne~+are compared with the experimental results to judge the quality of the wave function.The calculated results of photoionization cross section agree well with the RPA theoretical and experimental results.The phase shifts of photoelectrons moving in the Coulomb potential field of the target atom are calculated by R matrix,and the time delays of electrons emitted from different channels are obtained.In our calculations,electrons from 2p shell of Ne have a24.75 as time delay,compared with the 2s shell at 106eV,which is much better than other theoretical calculations and agrees well with the experimental result 21±5as.