Studies of U(C5H5)3Cl: Reorientational motions of cyclopentadienyl rings
| Autor: | B. Kanellakopulos, Philippe E. Raison, A. Delapalme, J. H. Williams, C.J. Carlile, R. Kahn, G. H. Lander |
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| Rok vydání: | 1994 |
| Předmět: | |
| Zdroj: | Molecular Physics. 81:369-383 |
| ISSN: | 1362-3028 0026-8976 |
| DOI: | 10.1080/00268979400100241 |
| Popis: | Inelastic neutron scattering experiments have been performed on polycrystalline samples of U(C5H5)3Cl, from 5 K to 300 K, to examine the quasielastic scattering that occurs from the hydrogen atoms in the cyclopentadienyl rings. Analysis of the scattering shows that a reorientational mode consistent with a 2π/5 process is present. At 300 K, the proton correlation time (τc) is 4·2 × 10-12 s and is associated with an activation energy (E A) of 4·9 kJ mol-1. Major differences in the dynamic behaviour of the rings have been observed in the following regions: 300 K > T > 245 K; 245 K > T > 78K; 78 K > T.. This is consistent with the observation of structural phase transitions at 78 K and 245 K. Below 245 K, the activation energy, which represents the potential barrier between sites, increases from 4·9 kJ mol-1 to 9 kJ mol-1. At the same time, 1/3 of the rings are blocked by intermolecular hydrogen bonds that arise during this first transition. At 78 K the second structural phase transition induces a triclinic s... |
| Databáze: | OpenAIRE |
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