The quantum yield for the production of NO 3 in the N 2 O 5 photolysis at 248 nm was measured to be unity. The concentration of NO 3 produced upon photolysis was measured using 662‐nm laser absorption. The quantum yields for O( 3 P ) production in the photolysis of N 2 O 5 at 248 nm, 266 nm, 287 nm, and 289 nm were also measured using resonance fluorescence detection of O( 3 P ). The quantum yield for O( 3 P ) decreased from 0.7 at 248 nm to 0.15 at 289 nm. It is postulated that N 2 O 5 photolysis at wavelengths less than 298 nm yields NO 3 + NO + O( 3 P )in addition to NO 3 + NO 2 .