Application of the RRKM Theory to Energized Ethylene Formed in the Vacuum-ultraviolet Photolysis of n-Paraffins

The Rice-Ramsperger-Kassel-Marcus treatment has been applied to the energized ethylene produced in the vacuum-ultraviolet photolysis of C2H6, C2D6, C3H8, C3D8, n-C4H10 and n-C4D10. The energy spread in the energized ethylene has been evaluated assuming modified statistical distribution of liberated energy among fragment species. The calculated nonequilibrium unimolecular decomposition rate constant for the process C2H4(C2D4)→C2H2(C2D2)+H2(D2) could satisfactorily reproduce the experimental pressure dependence of ethylene to acetylene ratio. Non-statistical kinetic energy Ek seems to appear for the primary decomposition of the n-paraffins. Its value ranges from zero for the elimination of methane and ethane from propane and n-butane, respectively, at 147.0 nm to about 25 kcal mol−1 for the elimination of hydrogen from ethane at 123.6 nm.