Quantum control of the dissociation of LiH molecules with two intense laser pulses

Abstract

The dissociation dynamics of LiH molecules induced by two overlapping femtosecond pulses is investigated based on the time-dependent quantum wave packet method. The first pulse induces population transfer from the ground state $X{\phantom{\rule{0.16em}{0ex}}}^{1}{\mathrm{\ensuremath{\Sigma}}}^{+}$ to the excited state $A{\phantom{\rule{0.16em}{0ex}}}^{1}{\mathrm{\ensuremath{\Sigma}}}^{+}$ which is coupled with the repulsive state $B{\phantom{\rule{0.16em}{0ex}}}^{1}\mathrm{\ensuremath{\Pi}}$ and the state $X{\phantom{\rule{0.16em}{0ex}}}^{1}{\mathrm{\ensuremath{\Sigma}}}^{+}$ by the second pulse. The two products $\mathrm{Li}(2p)$ and $\mathrm{Li}(2s)$ can be obtained via the ladder and $\mathrm{\ensuremath{\Lambda}}$ transitions, respectively, and the branching ratio of the products can be controlled by varying the second pulse frequency $\ensuremath{\hbar}{\ensuremath{\omega}}_{2}$. The choice of the intermediate state can affect the dissociation probability and angular distribution of fragments. As the second pulse intensity is increased, more products occur in other directions besides the directions $\ensuremath{\theta}={0}^{\ensuremath{\circ}}$ and ${180}^{\ensuremath{\circ}}$. The delay time of two pulses also has influence on the angular distribution.