THE SIMULTANEOUS 3-BODY DISSOCIATION OF CF2I2

The photodissociation dynamics of difluorodiiodomethane CF2I2 following 248 nm excitation were studied using the time-of-flight crossed laser-molecular beam technique. There is clear evidence that CF2I2 undergoes exclusively a simultaneous three-body dissociation. Two different reaction channels are observed: the dominant one (86%) yields CF2 + I(2P1/2) + I(2P3/2) while the less efficient one (14%) produces the same fragments but in the ground state CF2 + I(2P3/2) + I(2P3/2). The angle I-C-I between the recoil velocity vectors of the two departing I atoms was determined to be 120-degrees. The measured anisotropy parameters of beta-CF2 = -0.8 for the CF2 fragments and beta-I = + 1.1 for the I atoms (in both reaction channels) imply that the excited state symmetry of CF2I2* is B1 (molecular symmetry C2-upsilon) and also indicate that the excited state lifetime is significantly shorter than a rotational period. Furthermore, the dissociation energy for the rupture of both C-I bonds was determined to be D0 less-than-or-equal-to 53 kcal/mol. Based on this dissociation energy a heat of formation for CF2I2 of DELTA-H(f, 0 K)0 = -46 kcal/mol was calculated.