Spectral redshift of high-order harmonics by adding a weak pulse in the falling part of the trapezoidal laser pulse

摘要

We investigate the spectral redshift of high-order harmonics of the H2+ (D2+) molecule by numerically solving the non-Born-Oppenheimer time-dependent Schrodinger equation (TDSE).The results show that the spectral redshift of high-order harmonics can be observed by adding a weak pulse in the falling part of the trapezoidal laser pulses.Comparing with the H2+ molecule,the shift of high-order harmonic generation (HHG) spectrum for the D2+ molecule is more obvious.We employ the spatial distribution in HHG and time-frequency analysis to illustrate the physical mechanism of the spectral redshift of high-order harmonics.