35Cl NQR and mobility of partly chlorinated methyl groups in crystals

The temperature dependence of the ³⁵Cl NQR frequencies, their temperature coefficients, and spin-lattice relaxation times was studied for crystalline compounds Cl_xH_3?xCR with RC₆H₅, COOH, and CONH_2?y(CH₃)_y(x=1,2 and y=0,1,2) in the temperature range from 77 K to the sample melting points. It is found that for the mono- and dichloromethyl groups the shape of the experimental curves on the upper part of the temperature range often differs essentially from that predicted by the Bayer theory. These deviations may be interpreted as due to the appearance of the considerable anharmonicity of the autonomous librations of the groups mentioned.