The effect of reagent translation on product internal energy distributions: Laser fluorescence study of Al+O2

Abstract

The effect of incident translational energy on the product internal state distribution has been investigated for the reaction Al+O2→AlO+O. The incident energy is varied through the use of time-of-flight velocity selection of an Al atomic beam, and dye laser fluoresence excitation spectra are reported for AlO produced in a ’’beam-gas’’ arrangement under single-collision conditions. Relative cross sections and effective rotational temperatures are derived for the observed vibrational levels. On the average about 20% of the available energy appears as product vibration and 30% as product rotation. It is found that the AlO internal excitation increases with increasing incident kinetic energy but that ∼80% of the additional kinetic energy is disposed of as product translation and rotation. Comparison of the present results with previous theoretical work suggests that the Al+O2 reaction proceeds on an attractive surface with mixed energy release channeled primarily into product translation and rotation. The observation of a translational energy threshold for the production of AlO in the v=2 level has been employed to derive a lower bound to the AlO dissociation energy D0° (AlO) ?121.0±0.6 kcal/mole. With the help of previous work it is concluded that this lower bound is an equality and a value of 121–122 kcal/mole is recommended for the dissociation energy of aluminum monoxide.