原子基态函数对高次谐波谱影响的研究

Influence of the ground state wave function on the atomic high-order harmonic generation spectrum

强激光场和原子、分子相互作用产生高次谐波(High-order Harmonic Generation, HHG),高次谐波是重要的深紫外光的光源和探测原子分子动力学、原子分子结构等的有力工具.采用Lewenstein的理论,分别以s轨道和p轨道函数为基态函数,计算了惰性气体的高次谐波谱.计算发现,两种情况下得到的高次谐波谱结构有差别,即p轨道对应的谐波谱平台区出现一凹陷结构.分析表明,谱结构的凹陷位置依赖于p轨道的电子密度分布;进一步分析发现,高次谐波的平台结构取决于基态函数动量空间表达式的微分形式.这可为运用高次谐波分析轨道结构提供参考.

High-order harmonic generation(HHG) may occur during the interaction between an intense laser field and an atom or molecule;HHG has become an important xtreme utility vehicle(XUV) light source which can be used to probe atomic and molecular structures. In this paper, we investigate the effect of the radial distribution of electric density on the HHG spectra by calculating the HHG spectrum of noble atomic gases in a polarized laser field using s and p orbital functions as ground state wave functions. The results show that the form of the wave function does not influence the cutoff value of the harmonic spectrum, which is determined by the ionization threshold energy and the laser intensity. However,different types of orbital wave functions do lead to different envelopes for the HHG spectrum. In particular,there is an additional dip in the plateau area for the p orbital case compared with the spectrum for the s orbital case. By analyzing the formula for the HHG spectrum, we attributed the dip position on the HHG spectrum to the density distribution of the ground state wave function in momentum space. This work may shed light on applications for using the HHG spectrum to visualize atomic orbitals.