Journal of Physical Chemistry A, Vol.107, No.1, 19-24, 2003
Formation of molecular iodine from the two-photon dissociation of CI4 and CHI3: An experimental and computational study
The formation of electronically excited molecular iodine from the two-photon photodissociation of CI4 and CHI3 was investigated using dispersed fluorescence and ab initio calculations. Molecular iodine was formed in the D, D', and E ion-pair states from both CI4 and CHI3 In the photodissociation of CHI3, the intensity of the D' band is decreased and the E band is increased relative to those from CI4. This intensity shift is explained in terms of the energetics of the carbene photofragments. Intrinsic reaction coordinate calculations were performed at the MP2 level of theory using the LANL2DZ basis set to characterize the dissociation pathways for CI4 and CHI3. The results of the calculations show the presence of three transition states and an ion-pair isomer intermediate for both molecules. The structure of the transition states for the formation of molecular iodine is in agreement with the asynchronous concerted dissociation mechanism proposed by Dantus and co-workers for CX2Y2 halocarbons.