Title:
Hyperfine-changing Transitions in 3He II and Other One-electron Ions by Electron Scattering
Authors:
Bartschat, Klaus; Sadeghpour, H. R.
Affiliation:
AA(Department of Physics and Astronomy, Drake University, Des Moines, IA 50311, USA klaus.bartschat@drake.edu), AB(ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA hrs@cfa.harvard.edu)
Publication:
The Astrophysical Journal, Volume 788, Issue 1, article id. 69, 4 pp. (2014). (ApJ Homepage)
Publication Date:
06/2014
Origin:
IOP
Astronomy Keywords:
atomic data, atomic processes, dark ages, reionization, first stars, early universe, radio lines: general
DOI:
10.1088/0004-637X/788/1/69
Bibliographic Code:
2014ApJ...788...69B
Abstract
We consider the spin-exchange (SE) cross-section in electron scattering from 3He II,
which drives the hyperfine-changing 3.46 cm (8.665 GHz) line transition. Both
the analytical quantum defect method—applicable at very low energies—and
accurate R-matrix techniques for electron-He+ scattering are employed to obtain
SE cross-sections. The quantum defect theory is also applied to electron collisions
with other one-electron ions in order to demonstrate the utility of the method and
derive scaling relations. At very low energies, the hyperfine-changing cross-
sections due to e-He+ scattering are much larger in magnitude than for electron
collisions with neutral hydrogen, hinting at large rate constants for equilibration.
Specifically, we obtain rate coefficients of K(10 K) = 1.10 × 10–6 cm3 s–1 and
K(100 K) = 3.49 × 10–7 cm3 s–1.