Temperature dependence of the atmospheric photolysis rate coefficient for NO2

Direct measurements were made of the temperature dependence of the photolysis rate coefficient of NO2 (j1) at temperatures from −70° to 30° C in sunlight for relatively cloudless summer days in Boulder, Colorado. The ratio of the J1 values (J1(30°C)/j1(T°C) for T = −20° and −70° C are, respectively: 1.046±0.040 and 1.070±0.031 (95% confidence limits). The J1 ratios were independent of solar zenith angle (22° < Z < 47°). Theoretical estimates of the temperature dependent J1 ratios based upon recently reported cross section (σ) and quantum yield (ø) data are more consistent with these experimental measurements than those based upon the currently accepted σ and ø data.