We quantify the NO2 fluxes released into the gas phase during the continuous lambda similar to 300 nm photolysis of NO3- in submillimeter ice layers produced by freezing aqueous KNO3 sprays on cold-surfaces. Fluxes, F-NO2, increase weakly with [NO3-] between 5 less than or equal to [NO3-]/mM less than or equal to 50 and increase markedly with temperature in the range of 268 greater than or equal to T/K greater than or equal to 248. We found that F-NO2, the photostationary concentration of NO2- (another primary photoproduct), and the quantum yield of 2-nitrobenzaldehyde in situ photoisomerization are nearly independent of ice layer thickness d within 80 less than or equal to d/mum less than or equal to 400. We infer that radiation is uniformly absorbed over the depth of the ice layers, where NO3- is photodecomposed into NO2 (+ OH) and NO2-(+ O), but that only the NO2 produced on the uppermost region is able to escape into the gas phase. The remainder is trapped and further photolyzed into NO. We obtain phi (-)(NO2) similar to 4.8 x 10(-3) at 263 K, i.e., about the quantum yield of nitrite formation in neutral NO3- aqueous solutions, and an apparent quantum yield of NO2 release phi ' (NO2), similar to 1.3 x 10-3 that is about a factor of 5 smaller than solution OK data extrapolated to 263 K. These results suggest that NO3-photolysis in ice takes place in a liquidlike environment and that actual phi ' (NO2) values may depend on the morphology of ice deposits. Present phi ' (NO2) data, in conjunction with snow albedo and absorptivity data, lead to F-NO2 values in essential agreement with recent measurements in Antarctic snow under solar illumination.