Temperature‐dependent rate constant for the reaction of F atoms with HNO 3

Abstract : The kinetics of the reaction of F atom with HNO3, source of NO3 radicals widely used in laboratory studies, has been investigated at nearly 2.7 mbar total pressure of helium over a wide temperature range, T = 220-700 K, using a low-pressure discharge flow reactor combined with an electron impact ionization quadrupole mass spectrometer. The rate constant of the reaction F + HNO3 → NO3 + HF (1) was determined using both relative rate method and absolute measurements under pseudo–first-order conditions, monitoring the kinetics of F-atom consumption in excess of HNO3, k1 = (8.2 ± 0.4) × 10−12 exp((315 ± 15)/T) cm3 molecule−1 s−1 (where the uncertainties represent precision at the 2σ level, the estimated total uncertainty on k1 being 15% at all temperatures). The reaction rate constant was found to be in excellent agreement with the only previous temperature-dependent study. Experiments on detection of the reaction product, HF, have shown that NO3 and HF forming channel of the title reaction is the dominant, if not unique, on the whole temperature range of the study.