Optical absorption and emission spectra of trivalent ytterbium in various chelates are reported. The experimental energy levels of Yb3+are compared with predictions of electrostatic crystalhyphen;field theory and of a contact model of ligandhyphen;field theory. Good agreement is found between theory and experiment for the electrostatic crystalhyphen;field calculation. Poorer agreement is obtained using the ligandhyphen;field contact model calculation. The crystalhyphen;field calculation uses a single geometrical parameter thgr;. By using the calculations, xhyphen;ray results for other compounds, and the observed spectra, it is possible to obtain a reasonable estimate of the molecular geometry, which appears to be that of an octahedron distorted by shortening a threefold axis.
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