The simultaneous three-body dissociation of CF2I2

Abstract

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 °. The measured anisotropy parameters of βCF2=−0.8 for the CF2 fragments and βI=+1.1 for the I atoms (in both reaction channels) imply that the excited state symmetry of CF2I*2 is B1 (molecular symmetry C2v) 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≤53 kcal/mol. Based on this dissociation energy a heat of formation for CF2I2 of ΔH0f, 0 K=−46 kcal/mol was calculated.