Internuclear distance R-distribution of high-order harmonic generation from H2+ and its isotopes

Abstract

Internuclear distance (R) distribution of high-order harmonic generation from H2+ and its isotopes have been theoretically investigated. We found that in the presence of the few-cycle pulse, the harmonics mainly produce from R=2.0a.u. to R=4.5a.u. and the odd harmonics can be found in the harmonic spectra. With the increase of the pulse duration, the harmonics can be generated from R=2.0a.u. to the larger internuclear distance (e.g. R=15.0a.u.) and the even/odd harmonics can be obtained in the below/above-threshold harmonic regions. Moreover, the intensities of the harmonics can be enhanced in the presence of the multi-cycle pulse, but the intensities of the below-threshold harmonics can be reduced with the increase of the nuclear mass (e.g. D or T). The time-dependent nuclear motions, the ionization probabilities, the time-frequency analyses of the harmonic spectra and the R-dependent time-dependent wave functions have been shown to explain the R-distribution of the harmonic spectra from H2+ and its isotopes.