Temperature dependence of the atmospheric photolysis rate coefficient for NO2

Accurate values for the photolysis rate coefficient of NO2 (j1) are required for studies related to the observed imbalance in the photostationary state of O3, NO, and NO2 in the troposphere. Direct measurements of the temperature dependence of j1 at temperatures from -70 to 30 C were made in sunlight for relatively cloudless summer days in Boulder, Colorado. The ratios of j1 (30 C)/j1 (T C) for T = -10 C and -70 C, respectively, were 1.046 + or - 0.040 and 1.070 + or - 0.031. The j1 ratios were independent of solar zenith angle. Theoretical estimates of the temperature-dependent j1 ratios based upon recently reported cross section (sigma) and quantum yield (phi) data are more consistent with these experimental measurements than those based upon the currently accepted sigma and phi data.