Effects of L.E.T. and temperature in the radiolysis of cyclohexane. Part 1 .—Experimental results and comparison with predictions of diffusion kinetic models

Abstract

For low dose (∼3 × 10¹⁹ eV g^–1) irradiations of liquid cyclohexane at room temperature, G values of hydrogen, bicyclohexyl and cyclohexene were measured, using a number of different kinds of radiation, viz. ⁶⁰Co γ-rays, ⁴He ions of energy 58, 23, 8, 7, 3.03, 2.13, 1.53 MeV, 115 MeV ¹⁴N ions, and 22 MeV ²⁰Ne ions. The effect of changing temperature was determined for ⁶⁰Co γ-rays and for 3 MeV ⁴He ions. A search for high-molecular-weight products, determined by weighing, was also made in high-dose (1–9 × 10²¹ eV g^–1) irradiations at high dose rate (10²¹–10²² eV g^–1 s^–1), using 7 MeV ⁴He ions and 115 MeV ¹⁴N ions; initial G values of 0.65 and 0.80 respectively for conversion to polymer were found. In some experiments, G values of minor products, ethane, ethylene, acetylene, propane, propene, butane, butenes, n-hex-1-ene, and cyclohexyl-cyclohexenes were also measured. Attempts were made to correlate our results for changing L.E.T. and temperature, and the results of others using scavengers, with two diffusion models, in which the effect of L.E.T. is due to the competing reactions of thermal hydrogen atoms and excited molecules respectively. The latter model, in which L.E.T. effects are due to events prior to radical formation, was the more successful. G values for 115 MeV ¹⁴N ions were higher than expected on the basis of their overall mean L.E.T.; an analysis in terms of secondary electrons suggested that only a small part of the discrepancy was due to energetic secondary electrons, so that other radial track effects may occur with high-energy heavy ions.