Stimulated radiative association of He and C2+

Abstract

Stimulated radiative association of He and C${}^{2+}$ is investigated for temperatures $T=10\dots 10000$ K and a wide range of background-radiation temperatures, $T_b=0\dots 50000$ K. New HeC${}^{2+}$ potential energy curve is calculated by extrapolating the curves obtained by high-level ab initio calculations. Then the scattering cross section for the HeC${}^{2+}$ formation by stimulated radiative association of He and C${}^{2+}$ is calculated as a function of collision energy using a fully quantum mechanical approach. From these, the temperature-dependent rate coefficient of this process is determined for selected background temperatures. Barrier-less potential energy curve of HeC${}^{2+}$ supports 24 vibrational levels and 674 bound rovibrational states. 88 rovibrational resonances embedded in the potential continuum participate in the radiative association process. The rate coefficient for the spontaneous process monotonically decreases from $1.3\times 10^{-20}$ cm${}^3$ s⁻¹ to $2.6\times 10^{-22}$ cm${}^3$ s⁻¹. The rate coefficients for stimulated processes increase with increasing background-radiation temperatures by up to two orders of magnitude for $T_b=50000$ K.