Influence of ac Stark shift on below-threshold harmonic generation of H 2+ molecular ions in intense laser fields

The effects of laser-induced ac Stark shift on the high-order harmonic generation below the ionization threshold of H 2 + molecular ions are investigated. The results show that several sub-peak harmonics generated in the vicinity of odd harmonics are clearly observed. Combined with the synchrosqueez...

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Bibliographic Details
Published in:Laser physics letters 2023-08, Vol.20 (8), p.85302
Main Authors: Du, Ling-Ling, Wang, Zhi-Bing, Jin, Fa-Cheng, Wang, Guo-Li, Li, Peng-Cheng
Format: Article
Language:English
Subjects:
ac Stark shift
below-threshold harmonic generation
hydrogen molecule ions
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Summary:The effects of laser-induced ac Stark shift on the high-order harmonic generation below the ionization threshold of H 2 + molecular ions are investigated. The results show that several sub-peak harmonics generated in the vicinity of odd harmonics are clearly observed. Combined with the synchrosqueezing transform of the quantum time-frequency spectrum and a two-state model, we confirm that the transition between the first excited state related to ac Stark-shift and the ground state contributes to the sub-peak harmonics generation. In addition, we find some fine oscillatory structures of the sub-peak harmonic due to spectral interference. The sub-peak harmonics generation and spectral oscillations can be controlled by the laser intensity and the pulse duration. Our study provides a new alternative way to measure the energy difference of ac Stark shift between the excited state and the ground state of atoms and molecules in intense laser fields.
ISSN:1612-2011
1612-202X
DOI:10.1088/1612-202X/ace0b3