Hyperfine-changing transitions in ${}^3$He II and other one-electron ions by electron scattering

Abstract

We consider the spin-exchange (SE) cross section in electron scattering from ${}^3$He\,{\scriptsize II}, which drives the hyperfine-changing \hbox{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 $K(10\mathrm{K})=1.10\times 10^{-6}\mathrm{c}{\mathrm{m}}^3/s$ and $K(100\mathrm{K})=3.49\times 10^{-7}\mathrm{c}{\mathrm{m}}^3/s$.

arXiv comment9 pages, 5 figures, Accepted for Astrophysical Journal

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