ИСТИНА

Solid xenon is an interesting matrix for experimental studies of motional and chemical dynamics of atoms and radicals because of relatively large range of its thermal stability (up to 80 - 90 K). However, the EPR spectra of trapped radicals in natural xenon are not very informative because of strong line broadening due to the presence of magnetic nuclei, namely, 129Xe (I = ½) and 131Xe (I = 3/2). Recently we have suggested using monoisotopic 136Xe (I = 0) as a matrix for high resolution EPR spectroscopy over a wide temperature range [1]. In this contribution we present several examples of the EPR studies of small radicals in this unique matrix, which is similar to argon in terms of magnetic properties. 136Xe isotope (99.4%) was received from Russian State Research Center Kurchatov Institute. The radicals were generated from various precursors by fast electron or X-ray irradiation (no measurable difference in the spectral parameters were found for the two generation techniques). It was shown that elimination of magnetic nuclei provided especially good results in certain cases (e. g., for vinyl and ethynyl radicals), but did not improve the spectral resolution significantly in some other cases (OH, radical cations and larger radicals). The reason is that the line broadening for the latter species is determined mainly by other factors. Study of the temperature dependence of EPR spectra (in the range of 12 – 80 K) may give information on rotation and intramolecular inversion of radicals. The comparison of the spectra in solid argon and 136Xe matrix will be presented, and the electrostatic matrix effects on spin density distribution will be discussed on the basis of this comparison. [1] V. I. Feldman, F. F. Sukhov, A. Yu. Orlov, I. V. Tyulpina, Mendellev Communs, 18 (2008), 121–122