阈上电离谱与双色激光场频率的关系

Dependence of Above-Threshold Ionization Spectra on Frequencies of Two-Color Laser Fields

基于非微扰量子电动力学的频域理论,研究了原子在不同频率双色激光场中的阈上电离过程。当两个激光场的频率均远低于原子电离势时,阈上电离谱来自大量通道的干涉结果,两个激光场在电离过程中起到相同的作用。随着激光频率的增加,阈上电离谱逐渐呈现多平台结构,不同平台对应电子吸收不同高频光子的过程。当一个激光场的单个光子能量远大于原子电离势时,两个激光场在电离过程中起到不同的作用,高频激光场决定原子的电离概率,低频激光场决定原子阈上电离谱每个平台的宽度,且平台宽度可以很好地用能量守恒公式给出。

Based on the frequency-domain theory in nonperturbative quantum electrodynamics,we investigate the above-threshold ionization of an atom exposed to two-color laser fields of different frequencies.As both the frequencies of two laser fields are lower than the ionization potential of the atom,the above-threshold ionization spectrum comes from quantum interference among many ionization channels,and the two laser fields play same roles in the above-threshold ionization process.As the frequency of one of the two laser fields increases,the abovethreshold ionization spectrum shows a multiplateau structure gradually,which is from the contribution of atoms absorbing different photons of high-frequency laser field.As the frequency of one of the two laser fields is much higher than the atomic ionization potential,the two laser fields play different roles in the above-threshold ionization process,where the high-frequency laser field may determine the ionization probability and the low-frequency laser field may determine the width of each plateau that can be predicted by the energy conservation relationship.