Electron Spin Resonance Study on $\gamma$-Ray-Induced Ethyl Radical in Ethane Hydrate

概要

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Electron spin resonance (ESR) studies have been performed to investigate radicals induced in ethane hydrate irradiated by $\gamma$-rays at 77 K. Two ESR spectra are observed and identified as the induced ethyl radical ($g=2.0031\pm 0.0005$, $A_{\alpha\bot}=2.2\pm 0.1$ mT, $A_{\alpha\|}=2.5\pm 0.1$ mT, $A_{\beta}=2.7\pm 0.1$ mT) and induced atomic hydrogen ($g=2.0026\pm 0.0005$, $A=50.5\pm 0.1$ mT). From the results of ESR analysis and gas mass spectroscopy, it is concluded that the ethyl radical decays into butane by dimerization in the first-order reaction in the temperature region of 250–265 K. The activation energy of the decay reaction is $73.1\pm 6.3$ kJ/mol, which is near the dissociation enthalpy change of ethane hydrate to liquid water and gaseous ethane. This finding implies that ethane hydrate does not dissociate into ice but supercooled water in the present temperature region, similar to the dissociation of methane hydrate in our previous study.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2007-05-15