Kinetics of the reactions of CH3O and CD3O with NO

Abstract

The kinetics of the reactions of CH3O and CD3O with NO have been studied using a discharge flow reactor. CH3O and CD3O were detected using laser-excited fluorescence (LEF) near 300 nm. Total rate coefficients for the reaction of CH3O with NO were measured as a function of temperature (220–473 K) and pressure (0.75–5.0 Torr) of He or Ar. Total rate coefficients for the CD3O + NO reaction were measured at ca. 294 K over the pressure range 0.75–5.0 Torr He. Using molecular-beam mass spectrometry, the CH3ONO yield of the CH3O + NO reaction was measured at 297 K (0.5 and 1.0 Torr) and 223 K (1.0 Torr), showing that disproportionation to H2CO + HNO is the major channel at low pressures. These results were combined to obtain the following expressions for the disproportionation and low-pressure recombination rate coefficients.For the CH3O + NO reaction, kDISP=(1.3 ± 0.4)× 10–12 exp[(250 ± 100)/T] cm3 s–1, kIII0=(1.8 ± 1.3)× 10–29(T/300)–(3.2 ± 0.5) cm6 s–1For the CD3O + NO reaction at 294 ± 2 K kDISP=(3.0 ± 0.4)× 10–12 cm3 s–1 and kIII0=(2.5 ± 0.4)× 10–29 cm6 s–1 While the uncertainty associated with the measured rate coefficients is ca.± 15%, the product channel-specific rate coefficients obtained from these expressions are less certain, ca.± 50%.Using MBMS, the CH3NO2 yield of the CH3+ NO2 reaction was measured at 297 K (0.5 and 1.0 Torr) and 223 K (1.0 Torr). Combined with the previously reported rate coefficient, these results indicate a low-pressure, third-order recombination rate coefficient of (6 ± 2)× 10–29 cm6 s–1 in He at 297 K.