Electron spin resonance of NO2

Abstract

In this paper a discussion is given of the effect of molecular rotation on the E.S.R. spectrum of the NO₂ radical embedded in a polycrystalline host matrix of N₂O₄. The phenomenon is only observed if the host matrix containing the radical is properly annealed and slowly cooled to 77°k. Computer simulation of the spectrum shows unambiguously that in this temperature region a fraction of the radicals carries out a high frequency rotation, the remaining part being immobile. The temperature dependence of well-resolved spectra can be accounted for by assuming hindered rotation of the radical. Due to the different separations of the hyperfine components, the effect of rotation is different for the various parts of the spectrum.