A single crystal of 5% Pr³⁺ in LaCl₃ was grown by Stockbarger’s method and its absorption spectrum at 77° K. recorded in the region 4200–5400 Å on a grating spectrograph having a dispersion of 5 Å/mm. in the first order. Polarization of the absorption lines has also been obtained. In the group of lines arising from¹I₆ ←³H₄ transition, six more lines in addition to the four previously known have been observed. Satisfactory analysis of all these ten lines is given. One additional Stark level in¹I₆ is established at 21407 cm.⁻¹ withμ=1. For a few lines the polarization results obtained here do not agree with those of previous workers but fit in satisfactorily in the analysis.

The paper deals with an extension towards shorter wavelengths of the absorption spectrum of Nd³⁺ employing a 5% Nd³⁺ doped LaCl₃ crystal. Five new groups of lines have been recorded and the analysis and interpretation of one of these groups,viz., group O between 3010 and 3023 Å are given. The lines observed in this group are shown to be due to transitions from the ground level (⁴I_9/2) stark components (μ=5/2, 1/2 and 3/2) to the two stark components (μ=3/2, 1/2) of²D_3/2 level at about 33200 cm.⁻¹