Inelastic collisions of CaCl(X 2Σ+) with Ar: A collaborative theoretical and experimental study

Abstract

We investigate rotationally inelastic cross sections of CaCl(X 2Σ+) with Ar at a collision energy of 0.24 eV. Theoretical cross sections, determined by coupled states calculations based on an electron-gas description of the potential surface, are compared with experimental cross sections, determined in a molecular beam apparatus involving initial state selection by an electric quadrupole field and final state detection by laser-induced fluorescence. The agreement between theoretical and experimental cross sections is excellent, except for the e → e transitions with ΔN=even, which suggests a residual inaccuracy in the theoretical description of the second Legendre moment of the anisotropy in the potential. Both the theoretical and experimental cross sections clearly confirm a propensity toward conservation of the spectroscopic e/ f label. The sets of experimental and theoretical cross sections can be well fit by the sudden scaling relation, although the entire set of base cross sections can not be well represented by a simple power law.