The intratrack reactions of cyclohexyl radicals produced in the radiolysis of cyclohexane with helium and carbon ions have been examined using iodine-scavenging methods. It is found that in contrast to electron radiolysis, where most of the cyclohexyl radicals diffuse out of the radiolysis spurs and are readily scavenged at iodine concentrations of {approximately} 10{sup {minus}4}M, iodine interferes with the intratrack reactions of heavy ions only at much higher concentrations. From the concentration dependence, it is estimated that the intratrack reactions between radicals occur mainly on the 10{sup {minus}9}-10{sup {minus}7} s time scale for 10-MeV helium ions (LET {approximately} 10 eV/{Angstrom}) and at 1 order of magnitude shorter times for 10-MeV carbon ions (LET {approximately} 75 eV/{Angstrom}). These time scales establish the initial radical concentrations in the core of the track as being of the magnitude of 0.04 M for the helium ions and 0.8 M for the carbon ions. 27 refs., 8 figs.