High-order harmonic generation from molecular ions in the coherent electronic states.

The high-order harmonic generation from the tritium molecular ions in the coherent state has been numerically simulated by solving the three-state time-dependent Schrödinger equation based on the non-Born-Oppenheimer approximation. Two resonant pump pulses prepare the system in the coherent superposition of the and the states. A long-wavelength probe pulse is selected to generate the intense harmonics. By increasing the population of the state, the dependence of the harmonic spectra on pump-probe delay time tends to exhibit obvious redshift. In this work, not only is the physical image of harmonic emission from coherent wave packets established, but also a new physical mechanism of the redshift in long-wavelength region is revealed. Moreover, we present a scheme of manipulating the redshift to further verify the underlying mechanism. [ABSTRACT FROM AUTHOR]