Collisional deactivation of vibrationally excited ethylene produced from 121.6 nm ethylbromide photolysis system

Abstract

Collisional deactivation of vibrationally highly excited ethylene molecule produced from the 121.6nm photolysis of ethylbromide was studied at pressure region with presence of He, $CF_4$, $CO_2$, and $C_2H_5Br$ as collisional partners. By observing the ratio of decomposition to stabilization(D/S) of ethylene and comparing the calculated behaviors, we have obtained the average energy removed per collision by the collision partners. In the stepladder model the measured energies were found to be(in $cm^{-1}$/mole unit): $500cm^{-1}$ for He; $6500cm^{-1}$ for $C_2H_5Br$; $1700cm^{-1}$ for $CF_4$; and $1700cm^{-1}$ for $CO_2$. In the exponential model, the transfer energy of He was $700cm^{-1}$ by collision. The pressure dependence on the collision efficiency has been investigated and the energetics has also been studied. The RRKM calculation was used to analyze the experimental results quantitatively and the pressure dependence on product ratios was well explained by the calculation.