The reaction of Cs(82<i>P</i>) and Cs(92<i>P</i>) with hydrogen molecules

Abstract

The reactions of Cs(n2PJ), n=8, 9, J=1/2, 3/2 with H2 were studied by laser induced fluorescence of the nascent product. No difference was found in the reactivity of the J=1/2 and 3/2 states. The energies available to the reaction products were 11.5 and 16.9 kcal/mol for the n=8 and 9 states, respectively. CsH was found in the v=0 and 1 states but could not be detected in any higher vibrational state. The v=0/v=1 population ratios were 1/0.33 (n=8) and 1/0.42 (n=9). The products rotational temperatures were approximately the same as the ambient temperature of the reaction cell. Thus about 90% of the available energy is released as translation. From these data the following picture is derived. The mechanism is a primarily collinear abstraction and not an insertion. The large translational energy release is caused by a sudden switching on of repulsion when the H atoms are still close to each other. The reaction involves electron transfer, but at Cs–H distances not far from the equilibrium bond length and is therefore not a harpoon reaction in the usual sense.