Investigation of electron localization in harmonic emission from asymmetric molecular ion**Project supported by the National Natural Science Foundation of China (Grant No. 11404204), the Key Project of Chinese Ministry of Education (Grant No. 211025), the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20111404120004), the Natural Science Foundation for Young Scientists of Shanxi Province, China

Abstract

We theoretically investigate the electron localization around two nuclei in harmonic emission from asymmetric molecular ion. The results show that the ionization process of electron localized around one nucleus competes with its transfer process to the other nucleus. By increasing the initial vibrational level, more electrons localized around the nucleus D+ tend to transfer to the nucleus He2+ so that the ionizations of electrons localized around the nucleus He2+ increase. In this case, the difference in harmonic efficiency between HeH2+ and HeD2+ decreases while the difference in harmonic spectral structure increases. The evident minimum can be observed in the harmonic spectrum of HeH2+ compared with that in the spectral structure of HeD2+, which is due to the strong interference of multiple recombination channels originating from two nuclei. Time-dependent nuclear probability density, electron-nuclear probability density, double-well model, and time-frequency maps are presented to explain the underlying mechanisms.