Phys. Rev. Lett. 124, 173001 (2020)
Spontaneous Electron Emission from Hot Silver Dimer Anions: Breakdown of the Born-Oppenheimer Approximation
E. K. Anderson 1,*, A. F. Schmidt-May 2,1, P. K. Najeeb 1, G. Eklund 1, K. C. Chartkunchand 3, S. Ros´ en 1, Å. Larson 1, K. Hansen 4,5, H. Cederquist 1, H. Zettergren 1, and H. T. Schmidt 1,†
1 Department of Physics, Stockholm University, AlbaNova, SE-106 91 Stockholm, Sweden
2 Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, A-6020 Innsbruck, Austria
3 Atomic, Optical, and Molecular Physics Laboratory, RIKEN Cluster for Pioneering Research Wako-shi, Saitama 351-0198, Japan
4 Center for Joint Quantum Studies and Department of Physics, Tianjin University, 92 Weijin Road, Tianjin 300072, China
5 Department of Physics, University of Gothenburg, 41296 Gothenburg, Sweden
* emma.anderson@fysik.su.se
† henning.schmidt@fysik.su.se
Abstract
We report the first experimental evidence of spontaneous electron emission from a homonuclear dimer anion through direct measurements of Ag−2→Ag2+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 100 ms when ensembles of internally hot Ag−2 ions are stored in the cryogenic ion-beam storage ring, DESIREE, for 10 s. 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.
