Ab initio studies on photochemical reactions of Al atoms with H 2 molecules

Abstract

Potential energy surfaces are computed for the five lowest electronic states of the Al + H 2 system in its symmetric nuclear arrangement. Mechanisms of photochemical reactions of Al atoms with H 2 molecules are proposed, based on the calculated potential energy surfaces. The insertion reaction of the ground-state Al atom into the H 2 molecule is difficult under normal conditions. However, photoexcited Al atoms are capable of reacting with H 2 molecules along different pathways. The results obtained are consistent with experimental findings. The potential energy profiles of the dissociation reaction, AlH 2 → AlH + H, are traced by employing the UMP2 energy gradient method. Photocexcited Al atoms react with H 2 molecules along the 2 2A 1 state pathway, and the AlH 2( 2Σ g + ) formed dissociates easily into AlH( 1Σ) and H( 2S). The dissociation reaction of ground-state AlH 2 is difficult.