Optimal laser pulse design for transferring the coherent nuclear wave packet of H2+

Within the Franck-Condon approximation, the single ionisation of H-2 leaves H-2(+) in a coherent superposition of 19 nuclear vibrational states. We numerically design an optimal laser pulse train to transfer such a coherent nuclear wave packet to the ground vibrational state of H-2(+). Frequency analysis of the designed optimal pulse reveals that the transfer principle is mainly an anti-Stokes transition, i.e. the H-2(+) in 1s sigma(g) with excited nuclear vibrational states is first pumped to 2p sigma(g) state by the pulse at an appropriate time, and then dumped back to 1s sigma(g) with lower excited or ground vibrational states. The simulation results show that the population of the ground state after the transfer is more than 91%. To the best of our knowledge, this is the highest transition probability when the driving laser field is dozens of femtoseconds.