Production and quenching of excited photofragments of N2O

The photoabsorption and fluorescence cross sections of N2O are measured in the 105–160 nm region using synchrotron radiation as a light source. The quantum yields for producing the N2(B 3Πg →A 3Σ+u) and NO(B 2Πr →X 2Πr) emissions are determined. The quenching of emission intensity by various quenchers is investigated. The quenching rate constants of N2(B 3Πg) by H2 and N2 are measured to be 2.4×10−11 and 2.1×10−11 cm3/s, respectively. For the 120–140 nm excitation band the precursor of the NO β emission is attributed to ‘‘hot’’ O(1S), and for the 140–155 nm band it is N(2D). The ratios for the rate constant of hot O(1S) quenched by N2O, N2, Ar, H2, and He are measured to be 1:0.77:0.61:0.38:0.36, respectively. The lower limit for the rate constant of hot O(1S) quenched by N2O is estimated to be (2±0.8)×10−10 cm3/s. The quantum yield for producing the NO β emission from the reaction of hot O(1S) (produced at 125 nm) with N2O is about 0.4%. The O(1S) requires about 1.9 eV of kinetic energy to overcome the potential barrier between the reactants [O(1S)+N2O(X 1Σ+)] and the products [NO(B 2Πr) +NO(X 2Πr) ]. Based on the hot O(1S) kinetics, all the previous measurements as well as the current observations can be explained consistently.