Quenching Rate Constants of NF(a1Δ) at Room Temperature

Article abstract of DOI:10.1021/j100369a043

The gas-phase quenching rate constants for NF(a¹Δ) have been measured at 300 K for 60 reagent molecules.The experiments were done in a Pyrex glass flow reactor coated with halocarbon was using the 2F + HN3 reaction as a source of ND (a¹Δ).The rate constants span a wide range of values; the rate constants for most diatomic molecules are less than 1E-14 cm³ molecule^-1 s^-1, but more reactive molecules, such as C2H4, NH3, or P(CH3)3, have rate constants near 1E-11 cm³ moleczule^-1 s^-1.For polyatomic reagents that can act as Lewis bases, a correlation was found between the magnitude of the quenching rate constant and the base strength (measured as the proton affinity) of the molecule, which is evidence that the closed-shell (?_x²-?_y²) component of the NF(a¹Δ) state is involved in the quenching.The rate constants NF(a¹Δ) are larger than for the analogous O2(a¹Δ) state because of the more attractive interaction potentials between NF(a) and stable reagent molecules.A few experiments were done at ca. 200 K to demonstrate that this NF(a) source is suitable for low-temperature studies; the rate constants for O2, CO and C2H4 decreased with reduction in temperature.The 300 K bimolecular self-removal rate constant for NF(a¹Δ) was assigned as (5 +/- 2) * 1E-12 cm³ molecule^-1 s^-1; bimolecular energy pooling by NF(a) to give NF(b) is not an important quenching pathway.Quenching of NF(a) by F atoms has a small rate constant, (4 +/- 2) * 1E-13 cm³ s^-1.