Anisotropic Hyperfine Constant in ESR Spectrum of Irradiated Solution Grown Polyethylene

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Abstract
ESR spectra from the alkyl type free radical, –\underset(β)CH2–\underset(α)CH–\underset(β)CH2– , produced in irradiated crystals of high density polyethylene (Sholex 6000) grown from 0.025 wt. percent solution in xylene were studied, and anisotropic hyperfine splitting due to α-proton was investigated. Hyperfine splitting due to α-proton, D α, was obtained as |D α|=24-5(1-3cos 2ψ) in the unit of gauss, where ψ is the angle between external magnetic field and the direction of the c-axis of the molecule. Spin density at the carbon atom bearing the unpaired electron was calculated as 0.7 from analysis of the data of the spectrum for the mat of crystals. From the observed ESR spectrum for the alkyl type free radical produced in melt grown crystals, principal values of hyperfine coupling tensor were also estimated as follows; |A z |=13.6 gauss, |A x |=26.0 gauss, and |A y |=40.6 gauss. These values are very close to the calculated values.