Energy States of Solids with Particular Reference to the Energy States of Nd2(SO4)3–8H2O

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Abstract
The absorption spectrum of Nd2(SO4)3–8H2O crystals has been photographed at 20°, 78°, 169° and 298°K. The absorption lines occur in multiplets and originate in transitions from two low excited states as well as from the normal state. The excited levels of the basic multiplet are situated 77 and 260 cm—1 above the lowest state and undoubtedly arise through splitting of the normal state of the free Nd+++ ion in the electric field set up by its immediate neighbors in the crystal lattice. The positions of the observed levels are not in accord with conclusions of Penney and Schlapp from their study of the influence of crystal fields on the temperature variation of the paramagnetic susceptibility of Nd ion in neodymium sulfate octahydrate. Based in part upon the susceptibility measurements of Gorter and de Haas, Penney and Schlapp's work requires that the levels be at 0, 243 and 834 cm—1. If the data of Gorter and de Haas may be considered in error as regards absolute values the positions of the levels we have found are in excellent agreement with predictions of the theories of Van Vleck and Penney and Schlapp, and with the experimental results of Meyer and of Zernicke and James.