时间均匀采样的库仑修正强场近似方法

Coulomb-corrected Strong-field Approximation Method with Uniformly Sampled Time

摘要

本文利用标准的库仑修正强场近似方法（Coulomb-corrected strong-field approximation,CCSFA），即动量均匀采样CCSFA方法，和改进的时间均匀采样CCSFA方法对氩原子的阈上电离过程进行了研究。结果表明，两种采样策略计算得到的光电子动量谱和能谱基本一致，但是，由于两种方法得到的多次返回再散射电子的相对贡献不同，导致计算结果在光电子谱的高能部分有定量差别。通过分析，我们发现标准CCSFA方法在动量空间的采样是均匀的，但是对应到时间域却是不均匀的，其采样数量在激光场峰值处是极小值，这将导致在场峰值附近电离电子的贡献被低估。由于多次返回再散射电子的电离时间集中在激光场峰值附近，故其贡献在标准CCSFA方法中被低估。采用时间均匀采样方法则可以克服上述缺陷。

Abstract

In this paper, the above-threshold ionization process of argon atoms is studied using the standard Coulomb-corrected strong-field approximation (CCSFA), i.e. the CCSFA method with uniformly sampled points in momentum space, and the improved CCSFA method with uniformly sampled time. The results show that the photoelectron momentum and energy spectra calculated by the two sampling strategies are basically the same, but there is a quantitative difference between the calculated results in the high-energy part of the photoelectron spectrum due to the difference in the relative contributions of the multiple-return rescattering electrons obtained by the two methods. The analysis shows that the standard CCSFA method samples uniformly in momentum space, but corresponds to inhomogeneity in the time domain, and its sampling number is extremely small at the peak of the laser field, leading to an underestimation of the contribution of the ionized electrons near the peak of the field. Since the ionization time of the multiple-return rescattering electrons is concentrated near the peak of the laser field, their contribution is underestimated by the standard CCSFA method. The use of the time-uniform sampling method overcomes these shortcomings.

Graphical abstract

关键词

超短强激光 / 阈上电离 / 库仑修正强场近似 / 时间均匀采样

Key words

ultrashort intense laser / above-threshold ionization / coulomb-corrected strong-field approximation / time-uniform sampling

基金资助

国家自然科学基金(12274273)