Photodissociation of cyanogen: Angle and velocity distributions of state resolved fragments

The disposal of excess energy above the dissociation threshold into internal excitation and translation in a photochemical decomposition of C ₂N₂ has been determined by utilizing a technique by which measurements of the recoil velocity distribution for particular rotational states are possible. Simple phase space theory calculations appear to give a fairly good interpretation of the rotational energy distributions in a particular vibrational state, while the vibrational energy disposal is definitely nonstatistical with only about 63% of the total population predicted by statistical calculation in the first vibrational state and no excitation observed in the v = 2 state. Our experimental results support the previous predictions of high translational energy disposal (f_T = 75%) compared to a low or moderate product internal state excitations (f_R = 18.6%, f_v = 6.4%). We also measure the dissociation energy of C ₂N₂ to be 133 ± 1 kcal/mol rather than the previously reported 128 ± 1 kcal/mol.