HTFFR KINETICS STUDIES OF THE GE-N2O CHEMI-LUMINESCENT REACTION

The reaction Ge(43P0,1,2)+N2O→GeO(X 1Σ+, a 3Σ+, b 3Π1, A 1Π)+N2 (1) has been studied in a high-temperature fast-flow reactor (HTFFR) at temperatures from 475 to 920 K and pressures from 3 to 55 Torr. The following Ge removal rate coefficients were obtained (in units of ml molecule-1s-1): k1Ge(3P0)=(1.7±0.3)×10 -11exp[-(470±60)/T]; k1Ge(3P 1)=(8.1±1.3)×10-12exp[(120±40)/T]; k1Ge(3P2)=(1.2±0.4)×10 -11exp[-(200±100)/T]. While these k are considerably higher than those observed in the Sn/N2O reaction, the photon yields, Φ, are two to three orders of magnitude lower and, because of the resulting low chemiluminescence intensity, a complete kinetic expression could be obtained only for Φ(a): Φ(a)=(8.2±6.2)×102{1. 3×10-4+0.4×10-21[Ar]}{1+3.3×10 -15[N2O]}-1exp[-(2800±400)/T]. At [Ar]=(3 to 4)×1017 ml-1, we obtain Φ(b)=(0.23±0.13)(1+2.6×10-15[N2O]) 1exp[-(4900±200)/T]; Φ(A)=(0.033±0.025)(1+2. 8×10-16[N2O])-1exp[-(3800±380)/T]. At 545 K the following Stern-Volmer coefficients, τkQ N2O, for quenching by N2O were obtained (in ml molecule-1), GeO(a): (3.3±0.9)×10-15; GeO(b): (2.6±1.4)×10-15; GeO(A): (2.8±1.4)×10 -16. It is shown that reaction (1) is not an elementary reaction and a more detailed mechanism is proposed which, similar to that of Sn/N 2O, involves preferential reaction through the 3P 1 state and intermediate formation of a GeO* reservoir state from which the emitting GeO states are formed collisionally. The trends in the Group IVA element/N2O reaction kinetics are discussed. © 1980 American Institute of Physics.