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Abstract
We have investigated the local environments and the lattice dynamics of polycrystalline samples of pure thiourea (SC(NH2)2) and urea (OC(NH2)2)-doped thiourea using the techniques of 1H pulsed NMR. In the NMR frequency range of our investigation, the room temperature spin-lattice relaxation rate (1/T1) varies very sensitively, following the form predicted from the theory of the spectral density. This frequency dependence allowed us to calculate the correlation times of molecular reorientation in the pure and urea-doped thiourea lattices. The lineshapes showed the different environments of the protons in the two systems. We have also observed the effect of the 14N quadrupole-1H Zeeman level cross relaxation by directly taking NMR data at the magnetic field of the level crossing in thiourea.