Abstract
Depopulation of metastable He(2(3)S) and He(2(1)S) by radiative association with helium ions resulting in the formation of the He-2(+) molecular ions is investigated. Rate coefficients for spontaneous radiative association of the He-2(+) molecular ion on the spin-doublet manifold are presented as functions of temperature from 10 up to 500 000 K considering the association to rotational-vibrational bound states of the lowest doublet electronic states X-2 Sigma(+)(u) and A(2)Sigma(+)(g) from the continuum states of the excited doublet electronic states B-2 Sigma(+)(u) and D-2 Sigma(+)(u).
The dipole-driven processes B -> A and D -> A are compared to the quadrupole-driven processes B -> X and D -> X. For all considered temperatures, the dipole-driven process D -> A dominates over the other processes.
The rate coefficient for the quadrupole-driven process B -> X is at least three orders of magnitude larger than the rate coefficient of the dipole-driven process B -> A.