Photolysis of Gaseous Tetramethylethylene between 185 and 230 nm

Article abstract of DOI:10.1021/j150608a005

The far-UV photolysis of gaseous tetramethyletylene was carried out at 184.9 (mercury line), 202,4-213.8 (zinc lines), and 214.4-228.8 nm (cadmium lines).The photoproducts may be divided int two groups.In the first one, the quantum yield of each product decreases with increase in the total pressure.The proposed mechanism involves the α(C-CH3) or the β(C-H) fragmentation of the photoexcited molecule.Excited (CH3)2CC(CH3)CH2* radicals decompose further at 184.9 nm, and 2,3-dimethyl-1,3-butadiene and 3-methyl-1,2-butadiene are the products.Excited (CH3)2C=CCH3* radicals decompose further, and 2-butyne and isoprene are the products.Isomers 2,3-dimethyl-1-butene, 1,1,2-trimethylcyclopropane, and 3,3-dimethyl-1-butene are products of the second group; its quantum yield increases with an increase in the total pressure.The results support a collisionally induced preisomerization mechanism.Finally, it seems that both groups of products are formed from a different set of excited states