Abstract
Thermally oxidised polyethylene is known to exhibit two low-temperature dielectric relaxations, each of which has been attributed to tunnelling transitions of dipolar groups containing hydrogen and oxygen. The authors examined these in the subkelvin range and deduced the following tunnel splittings: Vincett's relaxation with H in poly (C2H4), 7.8+or-0.8 mu eV; the same in poly (C2D4), 5.9+or-0.6 mu eV; Carson's relaxation with D in poly (C2H4), 3.4 mu eV (geometric mean). The latter implies an acoustic coupling constant of 35 meV. Moreover the time constant of Carson's relaxation is found to depend not only on the 'impurity' hydrogen isotope but also on the host hydrogen isotope. For different combinations of isotopes it obeys a multiplicative law. The results are related to the polaron-like 'dressing' of tunnelling impurities.
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