Characterisation of octahedral hexahalo compounds.

We have recently investigated a series of compounds by inelastic neutron scattering, (INS) and conventional optical spectroscopies, to generate complete and unambiguous assignments for all the modes. One of the aims of the work was to see if there are any systematic trends that can be exploited to estimate the (usually) optically inactive mode ?6, if the other modes are known. A plot of ?5 vs ?6 shows that there is generally a good correlation between the two mode energies. We propose to measure the INS spectra of WF6 and MoF6, which will provide an unambiguous assignment of ?6 because of the absence of selection rules. We also propose to measure SF6 and WCl6, the former because it will provide confirmation of existing assignments and the latter because it will allow a comparison with WF6. In all four molecules, ?6 has only been observed indirectly from overtone and combination bands.

本研究团队近期采用非弹性中子散射（inelastic neutron scattering, INS）与常规光学光谱法对一系列化合物开展表征，旨在为所有振动模式完成完整且明确的指认。本工作的核心目标之一，是探索是否存在可被利用的系统性趋势，以便在其余振动模式已知的前提下，估算通常呈光学非活性的振动模式ν₆。以ν₅与ν₆的能量为横、纵坐标绘制的相关性图谱显示，两种振动模式的能量间普遍存在良好的相关性。我们计划测定六氟化钨（WF₆）与六氟化钼（MoF₆）的非弹性中子散射光谱，由于该类体系不存在振动选择定则，可对ν₆实现明确的指认。此外，我们还拟开展六氟化硫（SF₆）与六氯化钨（WCl₆）的非弹性中子散射光谱测定：前者用于验证已有的振动模式指认结果，后者则可用于与六氟化钨（WF₆）的光谱进行对比分析。在上述四种分子中，ν₆此前仅能通过泛频与合频带间接观测得到。