Abstract

Generally, driven by a specific laser waveform, a single-order harmonic from the atomic harmonic spectrum can be enhanced, caused by the multiple acceleration-recombination processes. However, in this paper, we found that, driven by the same waveform, a single-order harmonic enhancement is dependent on the internuclear distance of the hydrogen molecular ion. Particularly, at the equilibrium position of 2.0 a.u., a single-order harmonic enhancement with the smaller enhanced ratio can be obtained. As the internuclear distance increases from 3.0 a.u. to 7.0 a.u., a single-order harmonic enhancement is disappeared. When the internuclear distance is larger than 8.0 a.u., a single-order harmonic with a higher enhanced ratio appears again. Further theoretical analyses show that, a single-order harmonic is produced not only from the multiple acceleration–recombination processes of the single ionization, but also coming from the interference of the different ionization–acceleration–recombination processes. According to this principle, we explain the internuclear distance dependent on a single-order harmonic enhancement of the hydrogen molecular ion.

摘要

通常，由特定的激光波形驱动，可以通过多个加速复合过程来增强原子谐波频谱中的单次谐波。但是，在本文中，我们发现，在相同波形的驱动下，单次谐波增强取决于氢分子离子的核间距离。特别地，在2.0au的平衡位置处，可以获得具有较小增强比的单阶谐波增强。随着核间距离从3.0 au增加到7.0 au，单次谐波增强消失了。当核间距离大于8.0 au时，会再次出现具有更高增强比的单阶谐波。进一步的理论分析表明，单次谐波不仅产生于单个电离的多重加速-复合过程，而且还来自于不同电离-加速-复合过程的干扰。根据该原理，我们解释了取决于氢分子离子的单次谐波增强的核间距。