利用高次谐波实现分子的轨道成像:两中心干涉效应

Molecular orbital tomography using high-order harmonic generation:the effect of two-center interference

分子的轨道成像是科学研究中广为关注的主题.能否利用高次谐波来追踪化学反应的具体过程具有重要的实践意义,此外研究分子的轨道成像的理论基础还能够深化人们对原子的和分子的高次谐波辐射机制的理解.文章在简要回顾高次谐波研究历史的基础上,介绍了文章作者近期在利用高次谐波实现分子的轨道成像中的工作.文章作者通过数值地和解析地研究分子的高次谐波辐射的取向依赖检验了分子轨道成像的基本假设.研究显示,由于两中心干涉效应,高次谐波辐射过程中的分子的再碰撞电子波包与分子的价电子轨道的对称性和电离能密切相关.作为一个结果,分子的再碰撞电子波包的谱振幅可能和它的参考原子的再碰撞电子波包的谱振幅在某些能量区域显示很大的差别.这个发现对分子的轨道成像实验具有重要的意义.

The subject of molecular orbital tomography is of very broad scientific interest. The question of whether it is possible to follow chemical transformations in time using the effect of high-order harmonic generation （HHG） is of primary practical importance. Moreover, investigations of the foundations of molecular orbital tomography may lead to valuable deep insights into the mechanism of atomic and molecular HHG. We investigate the o- rientation dependence of molecular HHG both numerically and analytically, and show that the molecular recollision electronic wave packets （REWPs） in HHG are closely related to the ionization potential as well as the particular orbital from which it ionized. As a result, in some energy regions the spectral amplitude of the molecular REWP can be significantly different from its reference atom （ i. e. , that with the same ionization potential as the molecule under study） due to interference between the atomic cores of the molecules. This finding is important for molecular orbital tomography using HHG.