Femtosecond Time-Resolved Neighbor Roles in the Fragmentation Dynamics of Molecules in a Dimer

Abstract

How the neighbor effect plays its role in the fragmentation of molecular clusters attracts great attention for physicists and chemists. Here, we study this effect in the fragmentation of ${\mathrm{N}}_{2}\mathrm{O}$ dimer by performing three-body coincidence measurements on the femtosecond timescale. Rotations of bound ${\mathrm{N}}_{2}{\mathrm{O}}^{+}$ triggered by neutral or ionic neighbors are tracked. The forbidden dissociation path between ${\mathrm{B}}^{2}\mathrm{\ensuremath{\Pi}}$ and $^{4}\mathrm{\ensuremath{\Pi}}$ is opened by the spin-exchange effect due to the existence of neighbor ions, leading to a new channel of ${\mathrm{N}}_{2}{\mathrm{O}}^{+}\ensuremath{\rightarrow}\mathrm{NO}+{\mathrm{N}}^{+}$ originating from $\mathrm{B}^{2}\mathrm{\ensuremath{\Pi}}$. The formation and dissociation of the metastable product ${\mathrm{N}}_{3}{\mathrm{O}}_{2}^{+}$ from two ion-molecule reaction channels are tracked in real time, and the corresponding trajectories are captured. Our results demonstrate a significant and promising step towards the understanding of neighbor roles in the reactions within clusters.