Energy Dependence of Collisional Deactivation of Highly Vibrationally Excited Ethylcycloheptatriene

Article abstract of DOI:10.1021/j100295a036

Collisional self-deactivation of 7-ethylcycloheptatriene photoactivated to total internal energies of 123 kcal/mol (240 nm), 111 kcal/mol (265 nm), 106 kcal/mol (280 nm), and 100 kcal/mol (295 nm) has been investigated.The reaction products consisted of the positional isomers 1-, 2-, and 3-ethylcycloheptatriene and methyl-ethyl-substituted benzenes formed by structural isomerization.The pressure dependence of reaction products resulting from positional and structural isomerization was determined at each wavelength in a series of experiments without added bath gases.The yield of structural isomerization products decreased with increasing pressure, indicative of collisional stabilization of photoactivated ethylcycloheptatrienes.The ratio of positional to structural isomerization products increased with increasing pressure at fixed wavelength and increased with increasing wavelength at fixed pressure, consistent with a shorter lifetime for positional isomerization than for structural isomerization.Master equation calculations were done using RRKM theory and a stepladder model for deactivation.The model calculations predict that the average energy removed per deactivating collision, (ΔE), increases with increasing excess energy of photoactivated 7-ethylcycloheptatriene.