Study on gas phase collisional deactivation of O2(a1Δg) by alkanes and alkenes

Systematic measurements were made on the deactivation rate constants (k(Δ)) of O(2)(a(1)Δ) by homologous series of gaseous n-alkanes and 1-alkenes by using our recently developed quasi-static method. The results indicate that the k(Δ) values for alkanes are in direct proportion to the number of C-H bonds (N(CH)) in the molecules, while those for alkenes are not, but being still linear with N(CH), which is in good agreement with Schmidt's E-V energy transfer model. The direct proportion and linearity relationship, respectively, for alkanes and alkenes were well explained in terms of the type and number of their C-H stretching vibrational modes, together with their corresponding vibrational constants. The physical mechanism for the linearity and additivity in Schmidt's model was also discussed in detail. In addition, the k(Δ) values for alkanes were found to be evidently smaller than those for alkenes with the same number of carbon atoms (n) for n < 4, while the situation is quite the contrary for n > 4, which was also rationalized in terms of E-V energy transfer mechanism, together with their respective C-H stretching vibrational modes.