Quantum effects in the low temperature reorientation of N2− in KCl and KI |
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Authors: | RH Silsbee I Bojko |
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Institution: | Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York, U.S.A.;Pedagogical College of Opole, Poland |
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Abstract: | The electron paramagnetic resonance (EPR) spectra of KCl:N2? and KI:N2? were studied as a function of temperature and applied uniaxial stress in the temperature range 2–35°K. The molecular reorientation rates were determined for both 60 and 90° reorientations from the motional broadening and narrowing effects in the observed spectra. Although thermally activated in the range 15–35°K for KCl:N2?, the parameters deduced from the data are not consistent with a simple classical model of the motion. In both hosts the 90° rotation is markedly faster than the 60° reorientation, in conflict with simple models, but explicable in terms of the suppression of the tunneling matrix elements by polarization of the host crystal. In KI:N2?, the 90° reorientation is still apparent at 1·7°K and the spectra clearly show the influence of the symmetry of the nuclear spin states upon the reorientation kinetics, an effect predicted by Sussman. |
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