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.

We have performed an experimental investigation into the interaction of vacuum-ultraviolet synchrotron radiation with pyridine molecules in the gas phase. Specifically, a double-ion chamber spectrometer was used to measure the absolute photoabsorption cross sections and the photoionization quantum yields from the ionization threshold to 21.5 eV. Moreover, photoionization and neutral-decay cross sections in absolute scale were derived from these data. In addition, the fragmentation pattern was investigated as a function of the photon energy by using a time-of-flight mass spectrometer and the photoelectron-photoion coincidence technique. Thus, the absolute partial ionization cross sections for each ionic fragment were obtained. Comparisons are made with experimental data available in the literature.

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An experimental investigation of the processes leading tothe fragmentation of the singly ionized 1,1,1,2-tetrafluoroethane (HFC-134a, CH2FCF3) by EUV and soft X-rays is presented. HFC-134ais taken into consideration as the most convenient replacement for CFC-12 in refrigeration applications due to the fact that it has null ozone depletion factor. Dissociation of the singly ionized HFC-134amolecule was induced by valence, direct and indirect C 1s core photoionization or photoexcitation and the ionic fragments were detected in coincidence (PEPICO mode) with the ejected electrons without energy analysis. The singly ionized parent ion CF4CH2+can be detected even at photon energies above the C 1s threshold.

We discuss the use of a region of uniform and constant magnetic field in order to implement a two-state atomic polarizer for an H(2S) beam. We have observed that a device with such field configuration is capable of achieving an efficient polarization for a wide range of magnetic field intensities and atomic velocities. In addition, we establish a criterion that must be met to confirm a successful polarization. That is possible due to a specific beating pattern for the Lyman-α radiation expected for the outgoing two-state atomic beam.