Formation of the AlCl molecule through radiative association of Al with Cl

Abstract

ABSTRACT Detection of the AlCl molecule in IRC+10216 has been reported in the literature. We here report calculations of reaction rate constants for formation of AlCl through radiative association of Al and Cl for a temperature interval of 1000 to 14000 K. Potential energy and permanent/transition dipole moment curves were taken from the literature. Quantum mechanical and semiclassical/classical methods were used to obtain the reaction cross-sections and thermal rate constants, accounting for shape resonances with Breit–Wigner theory. Both the A$^1 \Pi \rightarrow$ X$^1 \Sigma ^+$ transition and the X$^1 \Sigma ^+\rightarrow$ X$^1 \Sigma ^+$ transition have been treated, with results showing that the former dominates for the temperatures considered in this study. Our rate constants are a factor of two to three larger than previously calculated values, where the latter were obtained without considering resonances or the X$^1 \Sigma ^+\rightarrow$ X$^1 \Sigma ^+$ transition. Our new values do however not change the previous conclusion that radiative association can only contribute modestly to the formation of AlCl under the given conditions.