Fragmentation of Valence and Carbon Core Excited and Ionized CH₂FCF₃ Molecule

The photofragmentation dynamics of 1,1,1,2-tetrafluoroethane (R134a) with photon energies from 12 eV up to 320 eV, surrounding the C 1s edge is discussed. The ionic moieties were measured in coincidence with the ejected electrons (PEPICO mode), and detected as a function of the photon energy. Around the C K core edge, the fragmentation profiles are examined regarding the site specific excitation of the CH₂FCF₃ molecule. In the present case, site-selectivity is favored by the distinct chemical environments surrounding both C atoms. NEXAFS spectrum at the C 1s edge simulation has been obtained at the TDDFT level and excited state geometry optimization calculations have been performed at the inner-shell multiconfigurational self-consistent field level. Our observations indicate that the C(H₂F) 1s excitation to a highly repulsive potential expels a fluorine atom leaving the heavier radical fragment C₂F₃H₂* which relaxes to the fundamental state of the ion C₂F₃H₂⁺. On the other hand, the excitation from the C(F₃) 1s carbon to a repulsive state in the C-C bond, leads to a C-C bond cleavage, explaining the observed site specific fragmentation.