Manipulating molecular rotational wave packets with strong femtosecond laser pulses

Abstract

Using three precisely timed laser pulses, we experimentally demonstrated that a strong femtosecond laser pulse can manipulate a coherent rotational wave packet. In the experiment, the first strong laser pulse created a coherent rotational wave packet from an initial thermal ensemble of ${\text{N}}_{2}\text{O}$ at room temperature. The second strong laser pulse manipulated the rotational wave packet. The third weak laser pulse probed the time evolution of the rotational wave packet by measuring the time-dependent alignment parameter. The pure heterodyne alignment signal and its Fourier transform spectrum were experimentally obtained and compared with the theoretical calculations. These results illustrated that the relative populations between even and odd rotational states can be controlled in the final rotational wave packet by precisely controlling the time delay between the first and the second laser pulses.