VUV Photofragmentation of Chloroiodomethane: The Iso-CH2I–Cl and Iso-CH2Cl–I Radical Cation Formation

Dihalomethanes XCH 2 Y (X and Y = F, Cl, Br, and I) are a class of compounds involved in several processes leading to the release of halogen atoms, ozone consumption, and aerosol particle formation. Neutral dihalomethanes have been largely studied, but chemical physics properties and processes involving their radical ions, like the pathways of their decomposition, have not been completely investigated. In this work the photodissociation dynamics of the ClCH 2 I molecule has been explored in the photon energy range 9-21 eV using both VUV rare gas discharge lamps and synchrotron radiation. The experiments show that, among the different fragment ions, CH 2 I + and CH 2 Cl + , which correspond to the Cl- and I-losses, respectively, play a dominant role. The experimental ionization energy of ClCH 2 I and the appearance energies of the CH 2 I + and CH 2 Cl + ions are in agreement with the theoretical results obtained at the MP2/CCSD(T) level of theory. Computational investigations have been also performed to study the isomerization of geminal [ClCH 2 I] •+ into the iso-chloroiodomethane isomers: [CH 2 I-Cl] •+ and [CH 2 Cl-I] •+ .