Charge-exchange collisions of 5 keV N+2 on Cs are examined using translational spectroscopy to identify the internal energy states of the fast neutralized products. Optical pumping of the reactant, N+2(A <- X) or Cs(2P <- 2S), is used to change selectively the electronic configurations and the reaction energy defect, while monitoring the resulting changes in the product state distribution. The N+2/Cs charge exchange yields N2 Rydberg states. A simple model of their formation would involve the transfer of the single outer electron in Cs into a Rydberg orbit built on the N+2 core. However, the present studies identify a surprising and highly efficient reaction mechanism in which the electronic configuration of the N+2 reactant is also changed during the electron transfer. This facile two-electron process, which occurs for both near-resonant and non-resonant reaction channels and has not been observed in other molecular charge-transfer reactions, is believed to be related to the very small energy separation between the ground and first excited electronic states of N+2.

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Journal J. Phys. B
Citation
van der Kamp, A. B, Beijersbergen, J. H. M, Cosby, P. C, & van der Zande, W. J. (1994). N+2 (A 2Pu ¬X 2S+g) excitation in the charge-exchange collision with caesium: two-electron effects at keV energies. J. Phys. B, 27, 5037–5053.