KINETICS OF FREE-RADICALS GENERATED BY IR LASER PHOTOLYSIS .1. REACTIONS OF C2(A3PI-U) WITH NO, VINYL CYANIDE, AND ETHYLENE

C2(α 3Πu) molecules are produced by multiple photon dissociation of either vinyl cyanide or ethylene with the focused output from a CO2 TEA laser. Their reaction with NO is reported in this paper. The total quenching rate coefficient of C 2(α 3Πu) by NO is determined both from laser induced fluorescence of C2(α 3Π u) and from the time resolved chemiluminescence from CN(B 2∑+) and CN(A 2Π) which are formed in the reaction, and is (7.5±0.3)10-11 cm3 molecule-1 sec-1. The vibrational energy disposal within the B 2∑+ and A 2Π states of CN is estimated from the resolved bands of the CN(B 2∑ +→X 2∑+) and CN(A 2Π→X 2∑+) emission systems. Vibrational levels of CN(B 2∑+) up to the limit ν = 5 but lower than ν′ = 10 are excited, accompanied by high rotational excitation. CN in the A 2Π state is excited to at least the 16th vibrational level. The reaction populates the A 2Π state about 7 times more efficiently than it does the B 2∑+ state. The reaction mechanism is discussed, and it is concluded that most of the electronically excited molecules are produced via the single step reaction C2(α 3Πu) + NO→CN(B 2∑+ or A 2Π) + CO(X 1∑ +). Quenching rate coefficients of C2(α 3Πu) by vinyl cyanide and ethylene are also reported. © 1979 American Institute of Physics.