The 367 nm Photochemistry of OClO Thin Films and OClO Adsorbed on Ice

Abstract

The 367 nm photochemistry of 70 monolayer (ML) OClO films and OClO adsorbed on ice is described. Gas-phase photoproducts formed during irradiation were detected with time-of-flight quadrupole mass spectrometry (TOF-QMS). For the OClO thin films, the major gas-phase photoproducts are OClO, OCl, and O 2 . The OClO and OCl TOF spectra could be fit to Maxwell−Boltzmann distributions, with temperatures of 967 ± 110 and 1721 ± 173 K, respectively. The O 2 TOF spectrum has fast and slow components that are fit to two Maxwell−Boltzmann distributions with temperatures of 70 ± 7 and 1165 ± 171 K. Photoproducts retained in the film or on the ice surface were characterized by reflection absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD). The predominant photoproducts retained in the films were identified as larger Cl x O y compounds, including ClClO 2, Cl 2 O 3, and Cl 2 O 4 . For OClO adsorbed on ice at coverages between 0.5 and 2 ML, photoexcitation at 367 nm results only in ClClO 2 formation without formation of other photoproducts of formula Cl x O y . The formation of ClClO 2 is consistent with irradiation of OClO aggregates on the ice surface.