Thick solid butane targets cooled at 77°K, containing known molar fractions of iodine, have been irradiated by monoenergetic rare gas ions with energies between 10 eV and 1500 eV. The nature and the importance of the fragmentation of the target molecules have been studied through the analysis of the formed organic iodides. TheGvalues for the overall yield of organic iodides are roughly the same for the various ions investigated and they are energy-independent between 150 eV and 1500 eV. However the mode of fragmentation depends strongly on the nature of the particles, the probability of C-C bonds rupture increasing with the LET. The neutralization energy of the incoming ions is also assumed to play a part in the radiolysis of the target.