Intermolecular interactions probed by rotational wavepackets in gas-phase clusters

Abstract The rotational dynamics of a molecule is sensitive to neighboring atoms or molecules, which can be used to probe the intermolecular interactions in the gas phase. Here, we real-time track the laser-driven rotational dynamics of a single N2 molecule affected by neighboring Ar atoms using coincident Coulomb explosion imaging. We find that the alignment trace of N-N axis decays fast and only persists for a few picoseconds when an Ar atom is nearby. We show that the decay rate depends on the rotational geometry of whether the Ar atom stays in or out of the rotational plane of the N2 molecule. Furthermore, we investigate the quantity effect of the neighboring atoms on the rotational dynamics and find that the laser-induced alignment of the N-N axis is immediately impeded when surrounded by two Ar atoms. The observations are well reproduced by solving the time-dependent Schrödinger equation after taking the interaction potential between the N2 and Ar into consideration. Our results pave the way to probe the environmental effect on a molecular level by directly visualizing the rotational dynamics.