Study on gas phase collisional deactivation of O_2(a ~1Δ_g) by alkanes and alkenes

摘要

Systematic measurements were made on the deactivation rate constants (k_Δ) of O_2(a~1Δ) 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.