Diffusion and Reorientations in Crystalline Acetylene.
ILLINOIS UNIV URBANA NOYES CHEMICAL LAB
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Crystalline acetylene in its two solid modifications was studied by means of temperature dependent static and rotating frame spin-lattice relaxation time measurements between 188-122K. The pressure of molecular motions was established in both phases. Two types of motions were observedin the high temperature cubic phase. Calculations of the longitudinal relaxation time behavior, as well as second moment considerations, for models of twofold flipping of the acetylene molecule, are both in agreement with the spherical reorientation model. In the low temperature phase relatively slow twofold flips or, less likely, spherical reorientation occurs. Motional parameters such as activation energies, pre-exponential factors, etc., were deduced.
- Atomic and Molecular Physics and Spectroscopy