Absolute hydroxyl quantum yields in the laser photolysis of nitrate, nitrite and dissolved hydrogen peroxide at 308 and 351 nm in the temperature range 278-353 K.
Abs. quantum yields for the formation of OH radicals in the laser photolysis of aq. solns. of NO3-, NO2-, and H2O2 at 308 and 351 nm and as a function of pH and temp. were measured. A scavenging technique involving the reaction between OH and SCN- ions and the time resolved detection by visible absorption of the (SCN)2- radical ion was used to det. the abs. OH yields. Together with the absorption coeffs. and an assumed actinic flux within atm. droplets of twice the clear air value, the partial photolytic lifetimes (tOH) of these species at 298 K are estd. as 10.5 days, 5.4 h, and 30.3 h for NO3-, NO2-, and H2O2, resp. These lifetimes will increase by a factor of 2 (NO3-, NO2-) and by 15% (H2O2) at 278 K. Using av. ambient concns. in tropospheric aq. droplets, the photolytic OH source strengths from these species are calcd. to be 2.8 * 10-11, 1.3 * 10-11, and 1.4 * 10-11 mol/L s for NO3-, NO2-, and H2O2, resp.
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