We report on the first direct investigation of the low-energy electron-induced production of neutral species from the chlorofluorocarbon CF2Cl2, commonly known as Freon-12 or CFC-12. Our experiments were motivated by a newly proposed hypothesis, which suggests that low-energy electrons produced by cosmic rays, in addition to UV−vis photons from the sun, interact with chlorofluorocarbons to produce chlorine atoms that subsequently destroy ozone in the Antarctic. Our experimental procedure involves low-energy (5−100 eV) electron irradiation of nanoscale thin films (∼10 Å thickness) of CF2Cl2 grown at 100 K on a molybdenum single crystal in an ultrahigh vacuum chamber (p ∼ 1 × 10-10 Torr). Post-irradiation temperature-programmed desorption experiments were used to identify C2F4Cl2, C2F3Cl3, C2F2Cl4, C2F3Cl, C2F2Cl2, and C2F4 as electron-induced radiolysis products of CF2Cl2. In contrast to previous studies of photon-induced dissociation, our studies of electron-induced dissociation demonstrate facile C−F bond cleavage in CF2Cl2. This finding may have implications for understanding the partitioning of Cl and F among source, sink, and reservoir gases in the stratosphere.

Case rates and coinfection rates have a significant effect on the PPV of a registry data-matching algorithm: PPV decreases as the case rate increases and coinfection rate decreases. Before conducting registry data matching, program staff should assess the case rate and coinfection rate of the population included in the data matching and select an appropriate matching algorithm.