Journal of Physical Chemistry A, Vol.105, No.23, 5606-5612, 2001
Avoided curve crossing between the A(1) and B-1 states in CF2Br2 photolysis at 234 and 265 nm
The photodissociation dynamics of CF2Br2 has been studied using a two-dimensional photofragment ion image technique for the two excitation wavelengths 234 and 265 nm. At 234 nm,three dissociation channels, i.e., the radical CF2Br + Br(P-2(J))(J = (1)/(2), (3)/(2)), the three-body CF2 + 2Br (P-2(J)) (J = (1)/(2), (3)/(2)), and the molecular elimination channel CF2 + Br-2, were observed with quantum yields of 0.84, 0.15, and trace, respectively. The difference between beta (CF2Br + Br (P-2(3)/(2))) = 0.65 and beta (CF2Br + Br (P-2(1/2))) = 0.80 suggests that the excited A(1) and B-1 states are strongly correlated by avoided curve crossing with a probability of 0.78. At 265 nm, the radical channel, the observed major primary dissociation channel, shows several components due to the transition close to the curve:crossing point. On the basis of observations at both wavelengths, we have proposed a photodissociation dynamics model of CF2Br2 after A-band excitation.