A photochemical reactor for studies of atmospheric chemistry

A photochemical reactor for studies of atmospheric kinetics and spectroscopy has been built at the Copenhagen Center for Atmospheric Research. The reactor consists of a vacuum FTIR spectrometer coupled to a 100 L quartz cylinder by multipass optics mounted on electropolished stainless steel end flanges, surrounded by UV-A, UV-C and broadband sun lamps in a temperature-controlled housing. The combination of a quartz vessel and UV-C lamps allows higher concentrations of O(1D) and OH than can be generated by similar chambers. The reactor is able to produce radical concentrations of ca. 8 × 1011 cm−3 for OH, 3 × 106 cm−3 for O(1D), 3.3 × 1010 cm−3 for O(3P) and 1.6 × 1012 cm−3 for Cl. The reactor can be operated at pressures from 10−3 to 103 mbar and temperatures from 240 to 330 K. As a test of the system we have studied the reaction CHCl3 + Cl using the relative rate technique and find kCHCl3+Cl/kCH4+Cl = 1.03 ± 0.11, in good agreement with the accepted value.