Photodissociation Dynamics of CF₂ClCHFI Using Slice Imaging Combined with a Hexapole-Oriented Molecular Beam

Photodissociation dynamics of 1-chloro-2-iodo-1,1,2-trifluoroethane (CF₂ClCHFI) were investigated at 267 nm by a slice imaging technique combined with an oriented molecular beam. The speed and angular distributions of the spin-orbit-selected I atoms were determined by analyzing the images. The anisotropic parameter was 1.67 ± 0.04 for the ground state of I(²P_3/2) and 1.94 ± 0.04 for the excited state of I(²P_1/2). A vector correlation study between the laser polarization and the dipole moment of the molecule revealed that the transition dipole moment in photoabsorption was found to be at 90° ± 15 to the molecular dipole moment, suggesting the transition dipole moment was nearly parallel to the C-I bond axis. The quantum yield for the excited state obtained from the observed signal intensities was estimated to more than 0.9 at this wavelength. The analysis of the kinetic energy release for both fragments indicated that a large amount of energy was distributed into the internal energy of the CF₂ClCHF· radical, which led to the secondary reaction of the C-Cl bond rupture. The study of the ground state of Cl atom formation via photolysis at 235 nm supported the existence of the secondary reaction. The results of the kinetic energy release of the I photofragments and the analysis of the image for the photofragment of the Cl atom suggested that the ground state of I atom formation mainly led to the secondary reaction of the C-Cl bond rupture through the short-lived CF₂ClCHF· radical. However, only part of the excited state of I atom formation involved the Cl atom formation through the long-lived CF₂ClCHF· radical.