Abstract/Summary

Nitrate radicals, NO3, were produced for the first time by 193 nm laser flash photolysis of N2O5 and HNO3. Detection was achieved due to NO3’s strong absorption at 622.7 nm confirmed by measurements of the absorption spectrum in the range of 617 to 625 nm using both NO3 precursors. Time-resolved kinetic studies allowed the determination of room temperature rate coefficients for the reactions of NO3 with 2-methylbut-2-ene and NO2 of (1.28 ± 0.11) × 10−11 and (8.4 ± 1.2) × 10−13 cm3 molecule−1 s−1, respectively. The rate coefficients compare well to previous measurements with alternative techniques suggesting that the reported method is valid and may be applied in follow-up studies. The rate coefficient for 2-methylbut-2-ene is compared to previous measurements and predictions for the alkene as well as the related alkenol. The new data confirm a previously suggested deactivation of the reactive site of the double bond if adjacent to an OH group. A calculated atmospheric lifetime for 2-methylbut-2-ene with respect to NO3-initated oxidation of less than 3 min suggests predominant removal by NO3 in the atmosphere.