Reaction dynamics of Al+O2→AlO+O studied by the crossed-beam laser-induced fluorescence technique

Abstract

Dynamics of the reaction, Al+O2→AlO+O, was studied by using the crossed-beam technique at five collision energies from 6.9 to 25.3 kJ/mol. The Al atomic beam was generated by laser vaporization and crossed with the O2 beam at a right angle. The product AlO was detected by laser-induced fluorescence of the AlO(B 2Σ+–X 2Σ+) transition and the rotational-vibrational distributions were determined. The observed rotational and vibrational distributions displayed greater populations in lower vibrational and rotational levels than expected statistically. Rotational distributions were also determined for two spin–orbit states of Al, Al(2P1/2) and Al(2P3/2), at two collision energies. At a collision energy of 12.2 kJ/mol, the higher energy spin–orbit excited state, Al(2P3/2), showed lower reactivity, i.e., about one-third of the ground spin–orbit state, Al(2P1/2). However, the rotational distributions for the two states were almost identical. Both the reactivity and rotational distributions for Al(2P1/2) and Al(2P3/2) became similar at a higher collision energy, 18.5 kJ/mol. These results suggest that the reaction of Al with O2 proceeds via an intermediate complex. Both spin–orbit states lead to the complex, lose memory of the initial electronic state, and provide identical rotational distributions.