Speaker :Chen Jing , researcher at the Beijing Institute of Applied Physics and Computational Mathematics.

Introduction:

Chen Jing is a researcher at the Beijing Institute of Applied Physics and Computational Mathematics. Graduated from the Department of Modern Physics, University of Science and Technology of China in 1992. In 1999, he received a Ph.D. in Science from the China Academy of Engineering Physics. From 1999 to 2001, he was a postdoctoral fellow in Theoretical Physics of the Chinese Academy of Sciences. From 2001 to 2004, he successively engaged in visiting research work at the Korea Advanced Institute of Science and Technology and the University of Kansas in the United States. In 2005, he joined the Beijing Institute of Applied Physics and Computational Mathematics. Mainly engaged in the theoretical research of the interaction between strong laser fields and atoms and molecules. Through close cooperation with the domestic strong field atomic and molecular experimental group, a comprehensive system of dynamic processes such as atomic and molecular ionization, Rydberg state excitation and high-order harmonic generation has been carried out. He has published more than 150 papers in academic journals. The research results were selected as the National Major Basic Research Progress during the Eleventh Five-Year Plan, the Top Ten Scientific and Technological Progresses of Chinese Higher Education Institutions in 2012, and the Important Achievements of China Optics in 2013. Presided over and participated in more than ten scientific research projects such as the National Natural Science Foundation of China, the National 973 Project, the National 863 Project, the Key Special Project of the Ministry of Science and Technology, and the Major Project of the Science and Technology Fund of the Chinese Academy of Sciences. In 2014, he won the National Outstanding Youth Fund. In 2015, he was selected into the National Hundreds and Thousands of Talents Project and was awarded the title of "Young and Middle-aged Experts with Outstanding Contributions". In 2016, he received special government allowance from the State Council. In 2018, he was selected as "Outstanding Expert" of China Academy of Engineering Physics.

Abstract:

We propose a quantum model based on the S-matrix theory to study the Rydberg state excitation (RSE) process in intense infrared laser field. In this model, the electron is at first pumped into continuum state by the laser field and then evolves in the external field. Most of the ionized electrons come out as free electrons (above-threshold ionization), however, some of the electrons may be captured in the Rydberg states. The second-order term of the S-matrix expansion well reproduces the intensity dependence of the RSE in 800 nm laser field obtained by numerical solution of time-dependent Schrödinger equation which shows two series of high and low peak structures depending on parties of the ground and Rydberg states involved. The probability of the capture process strongly depends on the relative phase of different quantum orbits, resulting in the peak structure in the intensity dependence of the RSE process. Experimental results with 800 nm laser field for Xe and Ar are in good agreement with our model calculation. The third-order term of the S-matrix expansion which takes into account the collision between the electron and the ionic potential before the capture process can well reproduce the TDSE and experimental results for longer wavelength, i. e., 1800 nm which shows an oscillation structure with period of 50 TW/cm2. Analysis shows that the coherent superposition of the contributions of such trajectories with different travel times (each generating one of the various low-energy structure peaks) causes the oscillation in the intensity dependence of the RSE yield, which is especially noticeable for longer wavelengths. Our work provides a new picture of the RSE in intense laser field: a coherent recapture process accompanying the above-threshold ionization.