Absorption Spectrum and Quantum States of the Praseodymium Ion. I. Single Crystals of Praseodymium Chloride

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Abstract
The structure of the polarization spectra exhibited by single crystals of anhydrous praseodymium chloride permitted the assignment of quantum states of the praseodymium ion because of the fact that the symmetry of the crystal fields had previously been determined by x‐rays. The crystals which were diluted with isomorphic, colorless lanthanum chloride, were grown from melts. Observations of transitions over the range from 2200 A to 18 000 A at the temperatures of liquid nitrogen and liquid helium led to the identification of seven upper states as well as the substates into which they were split by the crystal fields. The four lowest substates of the ground state also were characterized. The F triplet was found inverted. All the transitions were forced electric dipole in nature.