PULSE RADIOLYSIS OF NO - PRODUCTION OF NO2 AND N203 AND THE PRODUCTION AND RELAXATION OF VIBRATIONALLY EXCITED N0

Radiolysis of NO with a 30-nsec pulse of 2-MV electrons produces absorption bands attributed to NO2, N2O3, and vibrationally excited NO. In pure NO at 1 atm, most of the NO2 forms during the pulse, but the formation of N2O3 is slower (r=0.3 μsec). The NO2 is produced by the reaction of O atoms with NO, and the pseudo-first-order rate constant for formation of NO2 in an 11% NO-Ar mixture is slightly lower than that calculated from published values. The N2O3 comes from the equilibrium NO 2+NO=N2O2, which is achieved in <1 νsee, orders of magnitude faster than the previously estimated lower limit. The sum of yields of the two products (10.6±0.5 molecules/100 eV) was independent of the pulse dose, but the ratio G(NO2)/G(N2O3) increased with dose. This can be explained by a shift in the above equilibrium caused by the temperature increase produced by the pulse. Superimposed on the broad N2O3 band in the ultraviolet was a sharp band at 2362 Å, indicating population of the first vibrational level of NO. The relaxation lifetime was 5.8 μsec for 13% NO in Ar and 1.6 μsec for 41% NO, giving a quenching probability by NO of 2.1±0.2×10-4 compared with 3.6±0.4×10-4 reported by Basco, Callear, and Norrish. A small amount of absorption in the (0, 2) band at 2472 Å decayed with a lifetime ∼1.4 μsec, giving a probability for resonant vibration-vibration exchange of only ∼10-8.