Pulsed laser excitation of NO 2 (532–647 nm) or NO 3 (623–662 nm) in the presence of H 2 O was used to initiate the gas-phase reactions NO 2 * + H 2 O → products (R5) and NO 3 * + H 2 O → products (R12). No evidence for OH production in (R5) or (R12) was observed and upper-limits for OH production of k 5b / k 5 < 1 × 10 −5 and k 12b / k 12 < 0.03 were assigned. The upper limit for k 5b / k 5 renders this reaction insignificant as a source of OH in the atmosphere and extends the studies (Crowley and Carl, 1997; Carr et al., 2009; Amedro et al., 2011) which demonstrate that the previously reported large OH yield by (Li et al., 2008) was erroneous. The upper limit obtained for k 12b / k 12 indicates that non-reactive energy transfer is the dominant mechanism for (R12), though generation of small but significant amounts of atmospheric HO x and HONO cannot be ruled out. In the course of this work, rate coefficients for overall removal of NO 3 * by N 2 (R10) and by H 2 O (R12) were determined: k 10 = (2.1 ± 0.1) × 10 −11 cm 3 molecule −1 s −1 and k 12 = (1.6 ± 0.3) × 10 −10 cm 3 molecule −1 s −1 which is more than a factor of three smaller than one previously reported value.