Time-resolved kinetic studies on quenching of C2 (d3Î g) by alkanes and substituted methane molecules

C2 free radicals were produced by photolysis of selected precursors (C2Cl4) with the focused output from the fourth harmonic of a Nd: YAG laser at 266 nm. The generated C2 (a3Πu) radicals were then electronically excited to the d3Πg state with a Nd: YAG laser pumped dye laser at 516.5 nm in the (0,0) band of the C2 (d3Πg ← a3Πu) transition. The rate constants kq and averaged collision cross sections σq for collision quenching of C2 (d3Πg) by n-CnH2n+2 (n = 1-8) and CH4−nCln (n = 2-4) were measured at room temperature (298 K) by time-resolved laser-induced fluorescence in cell at total pressure of about 15 Torr. Formation cross sections of complexes for the C2 (d3Πg) and quenchers were calculated by means of a collision complex model. It was shown that the quenching rates of C2 (d3Πg) by alkane molecules increase with the number of C-H bonds of the molecules, which is in agree with that of the measured quenching cross sections.