Ultraviolet absorption spectrum of methylchloroform in the vapor phase

Ultraviolet absorption cross sections of methylchloroform CH3CCl3 were measured in the wavelength interval 180-240 nm and temperature range 210 to 295 K. Numerical values are given and compared with existing data at ambient temperature. Photodissociation coefficients were calculated for altitudes between 20 and 45 km and appear to be significantly lower than generally considered. Results show that the substantial decrease in absorption cross sections observed at low temperatures and lambda 210 nm has only a minor influence on overall photodissociation coefficients. Relative contributions of photodissociation and reaction with OH radicals as potential sinks for methylchloroform at stratospheric altitudes are also briefly discussed.