Photoelectron Imaging on Time-Dependent Molecular Alignment Created by a Femtosecond Laser Pulse

Rotational wave packet revivals on an excited electronic state have been measured by femtosecond time-resolved photoelectron imaging for the first time. The first full revival at 82 ps of $S_1$ $(n,{\pi }^{*})$ pyrazine was clearly observed in the time dependencies of the photoelectron intensity and the photoelectron angular distribution (PAD). The PAD, measured for laser aligned pyrazine, clearly reflects the different characters of ${\pi }^{*}$ and $3s$ molecular orbitals.