The photolysis of (CH3)2CDCH2CH3, (CH3)2CHCH2CD3, and of equimolarlpar;CH3rpar;2CHCH2CH3minus;lpar;CD3rpar;2CDCD2CD3mixtures has been investigated in the presence of NO at 1470 Aring; (8.4 eV), 1236 Aring; (10 eV) and at 1048ndash;1067 Aring; (11.54ndash;11.72 eV). Furthermore, in order to obtain quantitative information concerning the free radicals produced in the fragmentation processes, (CD3)2CDCD2CD3has been photolyzed at 1236 Aring; in the presence of various concentrations of H2S.Fragmentation of the excited isopentane molecule produced at 8.4 or 10 eV, as well as of the superexcited molecule formed at 11.54ndash;11.72 eV, yields mainly olefinic products and the following radicals, in order of decreasing yield: HCH3C2H5C3H7. In addition, on the basis of the various isotopically labeled products, it is concluded that methane, ethane, and propane are split off from the excited isopentane molecule by formation of (a) the corresponding carbene (1,2 elimination), or (b) the corresponding olefin (1,3 elimination). When the energy of the photon is increased from 8.4 to 10.0 eV, the 1,2hyphen;elimination processes become more important relative to the 1,3hyphen;elimination processes in all cases. At 11.54ndash;11.72 eV, the parent ion decomposes to form methane and ethane mainly by a 1,3hyphen;elimination mechanism. It is derived from the results that, in addition to the C4H8+and C3H6+ions formed by the latter fragmentation processes, the ions C4H9+and C3H7+are produced with ionhyphen;pair yields (M/N) of 0.15 and 0.06, respectively. The ionhyphen;pair yield of the parent ion is estimated to be 0.35. In contrast to observations derived from an earlier investigation of photoionization ofnhyphen;butane at 11.54ndash;11.72 eV, an increase in pressure from 0.15 to 15 torr has only a minor effect on the fragmentation of the parent ion.
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