Selective excitation of the ion pair surface in the intracluster Ca–HCl* harpoon reaction

Abstract

The excited state reaction of calcium with hydrogen chloride has been investigated in the specific conditions of a van der Waal complex formed in a supersonic jet after laser ablation of the metal. The reaction channel leading to ground state calcium chloride has been specifically studied in this work, by laser induced fluorescence. A very high vibrational distribution has been observed for CaCl with a maximum at v=30 and extending up to the energetic limit at v∼60. This high v population distribution has been modeled with the direct interaction direct repulsion model and corresponds to an immediate energy release occurring at the transition state, i.e., at the level of the ion pair ground state Ca+(2S), HCl− surface. This results from the observation of a continuous action spectrum for the formation of the high levels of CaCl after excitation of the complex in good agreement with the direct excitation of the ground state ion pair potential. It suggests that the potential energy surface promoting the ground state formation is different from the one leading principally to excited CaCl products already observed.