The Rare-earth Elements

Mossbauer spectroscopy of the rare-earth elements as a group has gained considerable attention from physicists. Successive addition of 4f-electrons along the series has little influence on many of the chemical properties, which are mainly those of a tripositive cation. However, such uniformity does not extend to properties derived from the electronic spin moment or from the atomic nucleus and therefore to the Mossbauer spectra. A resonance is known in at least one isotope of every rare-earth element except the first (cerium) and the last (lutetium). Furthermore, a resonance is often known for several isotopes, and in some instances for several transitions within a given isotope. It has therefore been possible to measure such properties as the nuclear magnetic moment for a large number of nuclear states within a small range of masses, and much of the work done has been directed to this end. The significance of the results to an understanding of the structure of the nucleus will not be considered here. Rather we shall describe the experimental phenomena and any derived nuclear parameters, together with the smaller proportion of data accrued which are chemically interesting. Numerical data for all transitions are summarised in Appendix 1.