Low-Energy Elastic and Fine-Structure Excitation Scattering of Ground-StateC+Ions by Hydrogen Atoms

Abstract

Cross sections are computed for the elastic and fine-structure excitation scattering of singly ionized carbon atoms by low-energy (less than 0.1 eV) hydrogen atoms. A close-coupling formulation is employed and the scattering equations are solved in a coupled-angular-momentum representation. The correct energy defect between the ${\mathrm{C}}^{+}\left({}_{}{}^2{}_{}{}^{}P\right)$ fine-structure levels is included. For the first time, both spin-change and long-range electrostatic coupling terms are explicitly included in the scattering equations. The calculated ${\mathrm{C}}^{+}$-H excitation cross section varies from 4.87×${10}^{-15\mathrm{}}$ ${\mathrm{cm}}^2$ at 0.01 eV to 2.86×${10}^{-15\mathrm{}}$ ${\mathrm{cm}}^2$ at 0.085 eV, and the maximum of almost 5.60×${10}^{-15\mathrm{}}$ ${\mathrm{cm}}^2$ occurs near 0.015 eV. The spin-change coupling, described herein, is found to be much more important than the long-range electrostatic coupling at all energies considered.