Linear energy transfer effect in radiolysis of cyclohexane

Abstract

Dimer formation in irradiated cyclohexane is influenced by the presence of iodine, which can act as a radical scavenger, reducing dimer yield and producing cyclohexyl iodide. The effectiveness of iodine is studied under a range of conditions (concentration of iodine, phase and temperature of cyclohexane) for y radiation, and compared with that for a irradiation of liquid cyclohexane. The results show that iodine is about equally effective in solid and liquid cyclohexane irradiated near the melting point, but is far less effective for low temperature irradiation, followed by warming. It is also less effective for a irradiation. The data are compared quantitatively with calculated values for a one-radical diffusion model, with good agreement. Reaction constants consistent with this model agree with those obtained directly from pulse radiolysis, while the estimates for the dimensions of a ionizing tracks are in conformity with those generally assumed in the radiolysis of water. The much lower efficiency of radical scavenging observed with a radiation is directly related to the l.e.t. effect frequently observed in radiobiology. The existence of a nonscavengeable (i.e. non-protected) fraction is explained without any necessity to invoke a different radiation mechanism.