Spontaneous electron emission from hot silver dimer anions: Breakdown of the Born-Oppenheimer approximation

• Main Authors: Anderson, E. K, Schmidt-May, A. F, Najeeb, P. K, Eklund, G, Chartkunchand, K. C, Rosén, S, Larson, Å, Hansen, K, Cederquist, H, Zettergren, H, Schmidt, H. T
• Format: Journal Article
• Language: English
• Published: 20-11-2019
• Subjects: Physics - Atomic and Molecular Clusters
• DOI: 10.48550/arxiv.1911.09170

Phys. Rev. Lett. 124, 173001 (2020) We report the first experimental evidence of spontaneous electron emission
from a homonuclear dimer anion through direct measurements of $\rm{Ag}_2^-
\rightarrow \rm{Ag}_2 + \rm{e}^-$ decays on milliseconds and seconds time
scales. This observation is very surprising as there is no avoided crossing
between adiabatic energy curves to mediate such a process. The process is weak
but 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 seconds. 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.