A new calculation of the radiative association rate of the CH+radical: comparison between semiclassical and quantal results (interstellar abundance)

Abstract

Ab initio potential curves and internuclear-distance-dependent oscillator strengths of CH⁺ are used to calculate the radiative association rate coefficient of this radical. A semiclassical treatment is developed which takes into account such collisional effects as non-adiabatic transitions between molecular states and tunnelling through the centrifugal barrier. A quantal formulation of the emission process is given, which takes into account the effect of the centrifugal potential on the vibrational nuclear wavefunctions. The value obtained for the radiative association rate coefficient cannot explain the discrepancy between the observed and theoretically deduced abundances of the interstellar CH⁺ radical.