Spontaneous Electron Emission from Hot Silver Dimer Anions: Breakdown of the Born-Oppenheimer Approximation.

E K Anderson,G Eklund,H T Schmidt,K Hansen,A F Schmidt-May,S Rosén,H Zettergren,Å Larson,K C Chartkunchand,H Cederquist,P K Najeeb

doi:10.1103/physrevlett.124.173001

Abstract

We report the first experimental evidence of spontaneous electron emission from a homonuclear dimer anion through direct measurements of Ag_{2}^{-}→Ag_{2}+e^{-} decays on milliseconds and seconds timescales. This observation is very surprising as there is no avoided crossing between adiabatic energy curves to mediate such a process. The process is weak, yet dominates the decay signal after 100ms when ensembles of internally hot Ag_{2}^{-} ions are stored in the cryogenic ion-beam storage ring, DESIREE, for 10s. The electron emission process is associated with an instantaneous, very large reduction of the vibrational energy of the dimer system. This represents a dramatic deviation from a Born-Oppenheimer description of dimer dynamics.

Highlights

In the Born-Oppenheimer approximation for molecules, the electronic and nuclear degrees of freedom are treated separately [1]
We report the first experimental evidence of spontaneous electron emission from a homonuclear dimer anion through direct measurements of Ag−2 → Ag2 þ e− decays on milliseconds and seconds timescales
Such processes occur on picosecond timescales at avoided crossings or conical intersections between adiabatic potential-energy curves or surfaces

Summary

Introduction

In the Born-Oppenheimer approximation for molecules, the electronic and nuclear degrees of freedom are treated separately [1]. The process is weak, yet dominates the decay signal after 100 ms when ensembles of internally hot Ag−2 ions are stored in the cryogenic ion-beam storage ring, DESIREE, for 10 s.

Results

Conclusion