Studies of the vapor phase photodissociation of azomethane-d(6)

The photodissociation of fully deuterated azomethane into two CD$\sb3$ radicals and N$\sb2$ was studied using transient CARS spectroscopy as a nanosecond resolved probe of the photoproducts. The Raman-active $\nu\sb1$ symmetric C-D stretching band of CD$\sb3$ radicals was observed and the following spectroscopic constants were obtained: $\nu\sb0$ = 2157.5 cm$\sp{-1}$, $\Delta$B = $-$0.026 cm$\sp{-1}$, $\Delta$C = $-$0.018 cm$\sp{-1}$, and X$\sb{12}$ = $-$5 cm$\sp{-1}$. Kinetic observations of the CD$\sb3$ photoproducts indicated that azomethane-d$\sb6$ photodissociates in a stepwise manner through a methyldiazenyl-d$\sb3$ radical intermediate. Indirect observations showed that this intermediate was formed promptly and found to have a lifetime of approximately 7 ns before decomposing into a CD$\sb3$ radical and N$\sb2$. A spectroscopic examination of N$\sb2$ photofragments revealed that their nascent vibrational distribution was 92 $\pm$ 5% in v = 0, 8 $\pm$ 5% in v = 1, and 0 + 5% in v $>$ 1