Title

Near-Threshold Rotational Excitation Of Molecular Ions By Electron Impact

Abstract

New cross sections for the rotational excitation of H+3 by electrons are calculated ab initio at low impact energies. The validity of the adiabatic-nuclei-rotation (ANR) approximation, combined with R-matrix wavefunctions, is assessed by comparison with rovibrational quantum defect theory calculations based on the treatment of Kokoouline and Greene (2003 Phys. Rev. A 68 012703). Pure ANR excitation cross sections are shown to be accurate down to threshold, except in the presence of large oscillating Rydberg resonances. These resonances occur for transitions with ΔJ ≤ 1 and are caused by closed-channel effects. A simple analytic formula is derived for averaging the rotational probabilities over such resonances in a 3-channel problem. In accord with the Wigner law for an attractive Coulomb field, rotational excitation cross sections are shown to be large and finite at threshold, with a significant but moderate contribution from closed-channels. © 2006 IOP Publishing Ltd.

Publication Date

10-9-2006

Publication Title

Journal of Physics B: Atomic, Molecular and Optical Physics

Volume

39

Issue

20

Number of Pages

4261-4273

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1088/0953-4075/39/20/023

Socpus ID

33750577520 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/33750577520

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