Peculiarities of EPR spectra of methyl radicals in quench-condensed krypton films

Abstract

Methyl radicals are trapped in the solid Kr film by simultaneous condensation of gaseous Kr and the products of the gas discharge in CH₄ doped Kr on the low temperature (4.2 K) substrate located at the center of the microwave cavity. The observed EPR spectrum is a superposition of broad-line and narrow-line series. At a low resonance microwave power, the latter one consists of four hyperfine components with nearly equal intensities, and shows small axial anisotropy of both g- and A-tensors. At a sufficiently large power, two central narrow lines split so that the narrow-line series takes an appearance recorded elsewhere for CH₃ in Ar at higher temperatures above 12 K. Simultaneously, the intensity of two central broad lines increases dramatically while the outer components become saturated. The possible explanation is discussed.