关键词: 高次谐波辐射/
阿秒脉冲/
短程势
English Abstract
Influence of atomic potential on the generation of high harmonic generation from the atoms irradiated by mid-infrared laser pulses
Liu Yan1,Jia Cheng2 3,
Guo Fu-Ming2,
Yang Yu-Jun2 3
1.College of Sciences, Jilin Institute of Chemical Technology, Jilin 132022, China;
2.Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China;
3.Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy (Jilin University), Changchun 130012, China
Fund Project:Project supported by the National Basic Research Program of China (Grant No. 2013CB922200), the National Natural Science Foundation of China (Grants Nos. 11274141, 11304116, 11534004), and the Jilin Provincial Research Foundation for Basic Research, China (Grant No. 20140101168JC).Received Date:19 October 2015
Accepted Date:24 November 2015
Published Online:05 February 2016
Abstract:By numerically solving the time dependent Schrodinger equation, the harmonic spectra generated from the atoms are obtained. The atomic potentials are modeled by a short-range potential and a long-range soft Coulomb potential, respectively. It is found that using the same laser parameters, the intensity of harmonic spectrum from the short-range atom is lower than the one from the long-range atom. However, in a high energy (near the cutoff) region of harmonic spectra, their conversion efficiencies are almost the same. The differences in emission intensity among harmonic spectra decrease as the harmonic energy increases. We calculate the time dependent probabilities of the ground state and ionization. It is found that the ionization probability of the long-range potential is larger than that of the short-range potential. There is no large difference in ground probability between the potentials of two models. The high harmonic generation is a stimulated process, and its intensity is proportional to the product between the amplitude for ground state and the amplitude of the continuum state. Thus the product of the long-range atom is larger than that of the short-range atom, and the emission spectrum presents a similar character.In order to analyze the mechanism of the intensity difference between two models, we perform a time-frequency analysis of the harmonic emission spectrum. The analysis is selected of the wavelet of the time dependent dipole moment. From the emission profile of the harmonic analysis, we find that the harmonic generated from long orbit plays a dominant role for the short-range atom. The amplitudes of electric field are large for the long orbit harmonic emission, thus the ionization mechanism of the atom is the tunnel ionization. For the short orbit, the instant field for the ionization is weak. Thus the short orbit plays a small role in the harmonic emission from the short-range atom. Using this feature of the short-range atom, we generate an isolated attosecond pulse. The short model atom is widely used to study the ionization of the plasma. Thus this work will contribute to the research on the high-order harmonic generation from the plasma.
Keywords: high harmonic generation/
attosecond pulse/
short-range potential
