Effect of laser pulse width on wave packet motion in femotosecond pump-probe pulses

The dependence of the wave packet process of three-level ladder K2 molecules on pulse width was investigated via time-dependent wave packet method, and was firstly quantified. There is no Autler-Townes splitting in the photoelectron spectrum with weaker pump intensity or shorter pulse width. The oscillation period of wave packet increases and the oscillation amplitude decreases with increasing pulse width. The pulse width affects Rabi oscillation, which results in the periodical change of the populations of the electronic state. Quantifying its effect on the population of the excited state shows that the change frequency varies with increasing pump intensity. The results illustrates that the needed population in electronic state of interested can be obtained by controlling pulse width, which provide some important basis for light manipulation of molecular processes experimentally.