Radiation-induced transformations of difluoromethane in noble gas matrices

Abstract Difluoromethane (CH2F2) is considered as an ecologically friendly alternative to conventionally used chlorofluorocarbons for various applications. Being photochemically inert in the broad UV range, this molecule can be decomposed only through the action of hard vacuum UV or ionizing radiation, while the corresponding mechanisms are poorly studied. In this work we report the results of model investigations of the X-ray induced decomposition of isolated CH2F2 in solid noble gas matrices at 6 K. The radiation-chemical yields of difluoromethane were found to decrease from 1.3 to 0.1 molecule/100 eV with decreasing the ionization energy of matrix (from Ne to Xe), which indicates significance of the “hot” ionic channels. Difluorocarbene (CF2) was detected as one of the principal radiolysis products in all the matrices, whereas the CHF⋯HF complex was detected in Ne, Ar, and Kr. Annealing of the irradiated samples results in thermally induced reactions of trapped H and F atoms yielding a number of various species, including the noble gas compounds. The radiolysis mechanism, nature of matrix effects and possible implications for atmospheric chemistry are discussed.