It is possible to obtain resolution of the order of 1–2 Å in the reflectance spectroscopy of powders by carefully controlling the experimental measuring techniques. One can then identify; optically, broad bands and narrow bands of the rare earths as being upper energy states and unperturbed 4f transitions. It is even possible to show various degrees of perturbation of 4f energy-states of a given rare-earth ion by observing Stark states which may vary from 5–90 Å in half-width. However lack of polarization data make positive identification of these Stark states impossible.
JørgensenC. K.PappalardoR., and RitterhausE., Z. Naturforsch.20a, 54 (1965); JørgensenC. K., Mol. Phys.5, 271 (1962); JørgensenC. K., Orbitals in Atoms and Molecules (Academic Press, London, 1962); JørgensenC. K., Prog. Inorg. Chem.4, 73 (1962); JørgensenC. K., Proc. 5th Rare Earth Conf.; Session S-l p 1. Ames, Iowa (1965); RyanJ. L. and JørgensenC. K., J. Phys. Chem.70, 2845 (1966).
2.
LohE., Phys. Rev.154, 270 (1967).
3.
LohE., Phys. Rev.158, 273 (1967).
4.
LuckieschM., Applications of Germicidal Erythemal and Infrared Energy (D. Van Nostrand Company Inc., New York, 1946) p. 383.
5.
Available from Bausch & Lomb, Rochester, N. Y.
6.
WykoffR. W. C., Crystal Structures (John Wiley & Sons, Inc., New York, 1964).
