Neutron inelastic scattering studies of globular compounds
The use of neutron inelastic scattering measurements to determine the nature of the solid-state transitions in globular compounds is proposed and exemplified. Patterns were taken of the high- and low-temperature phases of solid cyclohexane, 2-2-dimethylbutane, and 1-4-diazo-bicyclo-(2.2.2)-octane. T...
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| Formato: | JOUR |
| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_00219606_v38_n7_p1685_Becka |
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| Sumario: | The use of neutron inelastic scattering measurements to determine the nature of the solid-state transitions in globular compounds is proposed and exemplified. Patterns were taken of the high- and low-temperature phases of solid cyclohexane, 2-2-dimethylbutane, and 1-4-diazo-bicyclo-(2.2.2)-octane. The first two have broad inelastic scattering peaks in the low-temperature phase. In the high-temperature phase these peaks disappear and the elastic peak broadens markedly. These changes are attributed to "quasi-free- rotation" of the molecules. Inelastic peaks do not appear in 1-4-diazo-bicyclo-(2.2.2)-octane, and the elastic peak does not broaden appreciably in the high-temperature phase. Self-diffusion coefficients D 3=4.5×10-5 cm2/sec for cyclohexane and D3=8.6×10-5 cm2/sec for 2-2-dimethylbutane were determined from the patterns of the liquids at 300°K using the "small motions" approximation. These values are larger than those obtained from NMR measurements, presumably as a result of irreversible rotation of the molecules. |
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