Knowledge Bank

NMR line shapes and spin-lattice relaxation times have been studied for methyl chloroform and methyl trichlorosilane dissolved in hexachloropropene from $4.2\circ K$ to the melting point. The small intermolecular magnetic dipole-dipole interactions introduce line broadening of only $\sim$ 0.7 G and thus permit details of the line shapes to be resolved. Line shapes charcteristic of a rigid nonrotating triangle of spins are found below $77\circ K$ for methyl chloroform, but methyl trichlorosilane exhibits a “fast rotation” spectrum even at 4.2$\circ K$. The effects of thermally activated rotation and tunneling on the line shapes and spin-lattice relaxation times for these systems are discussed.