Imaging the Breakdown of Molecular-Frame Dynamics through Rotational Uncoupling

TL;DR

This paper visualizes the breakdown of molecular-frame dynamics caused by rotational-electronic uncoupling in Rydberg states, revealing non-Born-Oppenheimer behavior through time-resolved photoelectron imaging of N₂.

Contribution

It demonstrates the first direct observation of non-Born-Oppenheimer dynamics in molecular Rydberg states via photoelectron imaging.

Findings

Photoelectron angular distribution differs from typical molecular orbitals.

Electron precession around the anisotropic potential is observed.

Breakdown of molecular-frame dynamics is visualized in the time domain.

Abstract

We demonstrate the breakdown of molecular-frame dynamics induced by the uncoupling of molecular rotation from electronic motion in molecular Rydberg states. We observe this non-Born-Oppenheimer regime in the time domain through photoelectron imaging of a coherent molecular Rydberg wave packet in $\textrm{N}_2$. The photoelectron angular distribution shows a radically different time evolution than that of a typical molecular-frame-fixed electron orbital, revealing the uncoupled motion of the electron as it precesses around the $averaged$ anisotropic potential of the rotating ion-core.