Direct evidence for channel-coupling effects in molecules: electron impact excitation of the a″ 1Σ+g state of N2

Creators: Khakoo, M. A.; Wang, S.; Laher, R.; Johnson, P. V.; Malone, C. P.; Kanik, I.

Abstract

New measurements of differential cross-sections for excitation of the a″ 1Σ+g (v' = 0, 1) state in molecular nitrogen reveal a cusp-like angular distribution. This feature is distinctly observed for the first time in the present electron energy-loss experiment as a result of finer scattering angle grid and impact energy coverage than previous measurements. This feature is similar to that observed in atomic targets such as He, Hg and Ba. The observed phenomenon suggests an interference effect related to configuration–interaction coupling between lower and excited states that are of the same symmetry. It is hoped that the present work will stimulate theoretical investigations into the physics that governs this cusp-like behaviour.

Additional Information

Fast Track Communication. Copyright © Institute of Physics and IOP Publishing Limited 2007. Received 31 March 2007, in final form 15 April 2007. Published 30 April 2007. Print publication: Issue 10 (28 May 2007) This work was performed at the California State University, Fullerton (CSUF) and at the Jet Propulsion Laboratory (JPL), California Institute of Technology (Caltech), under a contract with the National Aeronautics and Space Administration (NASA). We gratefully acknowledge financial support through NASA's Outer Planets Research program and the National Science Foundation, under grant no NSF-PHY-RUI-0653450. This research was performed while CPM held a NASA Fellowship at JPL. We acknowledge the spectral data supplied to us, for the higher-lying states of N2, by Dr B R Lewis (Australian National University) and thank Dr D V Fursa (Murdoch University) for supplying Convergent Close-Coupling calculations for Ba. The authors are grateful to Drs C Winstead and V McKoy (Caltech) for stimulating discussions.

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