Hydrogen peroxide formation following the vacuum ultraviolet photodissociation of water ice films at 90 K

The production of gaseous OH radicals from the 300-350 nm photodissociation of H2 O2 that was photolytically produced on a water ice surface following the 157 nm photolysis of water ice at 90 K was directly monitored using resonance-enhanced multiphoton ionization. The translational energy distribution estimated by the time-of-flight spectrum of the OH products is represented by a Maxwell-Boltzmann energy distribution with a translational temperature of 3750±250 K. The rotational temperature was estimated by a spectral simulation to be 225±25 K. Surface defects produced by HCl deposition on the water ice contributed to the higher production rate of H2 O2 in the 157 nm photoirradiation of water ice while surface coverage caused by C D3 OH deposition decreased the H2 O2 production rate.