Knowledge Bank

The reaction of velocity selected A1 atoms with $O2$ has been studied by laser-induced $fluorescence1$ so that individual A10 internal states could be observed. Velocity-selection is achieved by a recently developed time-of-flight (TOF) $technique2$ utilizing pulsed laser excitation. Spectra of the A10 B-X system have been taken at several A1 velocities, and the intensities of the $\Delta \nu =+1$ band heads as a function of A1 velocity have also been measured. Using two different methods of analysis, we have arrived at a value of $D0\circ (A10)=123\pm 1$ kcal/mole. One method employs the excitation spectra to find the maximum internal energy of A10 formed, while in the other, the translational energy threshold for formation of v = 2 A10 is determined. The present value agrees well with previous determinations by other methods; moreover, the present experiment considerably narrows the permissible range of values for $D0\circ (A10)$.