with 20% n-decane-h22 have been examined by means of capillary GLC coupled with mass specfrometry. Analysis of the results indicates that protiated alkyl radicals are selectively formed. This confirms the data obtained by radiolysis at 7 7 K. The selective abstraction of hydrogen from a C-H bond on the solute molecules by the attack of D atoms which are formed by the radiolysis, occurs at 77 K. However, at 4 K, data from IWASAKI suggest an other explanation. The primary process is not selective but conversion of deuterated to protiated alkyl radicals takes place at 200 K.