Wavepacket-shaping by a frequency-chirping technique

The excited- and ground-state wavepacket behavior caused by frequency-chirping of a femtosecond laser pulse in H2− photodissociation has been investigated using a time-dependent method. A positive-chirping laser pulse is found to enhance the population transfer between two energy surfaces and also decrease the ground-state wavepacket deformation under a strong laser field. In contrast, a negative-chirping laser pulse will induce a larger ground-state wavepacket deformation. In addition, the excited-state wavepacket created by a positive-chirping pulse has less spatial dispersion, while a negative-chirping laser pulse will generate a more dispersed excited-state wavepacket. This can help us shape a wavepacket, which is of significance in laser control of molecular dynamics.