Internuclear distance dependent on a single-order harmonic enhancement of hydrogen molecular ion
Liqiang Feng, Yan Qiao, Liang Li
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.