とぴっくす: 放射線照射試料に特徴的な動的核スピン偏極機構

熊田 高之, 能田 洋平, 石川 法人
2013 Biannual Journal of Japanese Society of Radiation Chemistry  
We have studied dynamic nuclear polarization (DNP) behavior of polyethylene irradiated with electron and particle beams. Both of the growth and decay rates of the nuclear polarization of the polyethylene samples linearly increase with increasing concentration of alkyl free radicals produced by the radiolysis, whereas those of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-doped samples are proportional to the square of the concentration of the TEMPO. This result suggests that the DNP of the
more » ... ated polyethylene is caused by the pair of the alkyl radicals produced by the radiolysis -CH 2 -CH 2 -CH 2 -→ -CH 2 -ĊH-CH 2 -+ Ḣ, and the subsequent hydrogen abstraction reaction -CH 2 -CH 2 -CH 2 -+ Ḣ → -CH 2 -ĊH-CH 2 -+ H 2 , whereas the TEMPO-doped sample is polarized by pairs of unspecified TEMPO radicals accidentally located nearby. We suggest that higher polarization is expected by optimizing irradiation temperature, on which the radical-radical distance in the pair depends.
doi:10.32157/jsrc.95.0_21 fatcat:cgzptbx3qzbspkjhvfr43enumm