Radiolysis of Cyclooctane with γ-Rays and Helium Ions

Article abstract of DOI:10.1021/j100084a016

Iodine scavenging techniques have been used to examine the role of the cyclooctyl radical in the radiolysis of cyclooctane with γ-rays and with 5-20-MeV helium ions.In γ-radiolysis about 70percent of the total yield of 6.6 cyclooctyl radicals/100 eV are scavenged with E-4 M iodine, which agrees well with other studies on cycloalkanes that show most of the radicals produced in these systems react in the bulk medium at times longer than 1 μs.However, it is found that 2.5 radicals/100 eV (38percent) are produced by H atom precursors as copmpared to a value of 1.5 cyclohexyl radicals/100 eV (25percent) in cyclohexane.With 10-MeV helium ions (average LET of 106 eV/nm), only 8percent of the cyclooctyl radicals survive longer than a few microseconds due to the increased initial radical concentration in the helium ion track.The yield of the cross-bridged product bicyclo<3.3.0>octane (pentalane) was found to be independent of iodine concentration up to 0.03 M with both types of radiation.However, the pentalane yield found with 10-MeV helium ions was only one-third of that found in γ-radiolysis.The most likely reason for this result is the decreased yield of singlet-state formation due to the enhanced probability of cross combination reactions of electron-cation pairs in the high-density region of the helium ion track.