S01Level ofPr3+in Crystals of Fluorides

Abstract

The $^{1}S_{0}$ level of the trivalent praseodymium ion ${\mathrm{Pr}}^{3+}$ in Ca${\mathrm{F}}_{2}$ and La${\mathrm{F}}_{3}$ crystals has been identified in the absorption spectrum and in the excitation spectrum of orange fluorescence. It appears as a small peak near the $4f\ensuremath{\rightarrow}5d$ band of ${\mathrm{Pr}}^{3+}$ at 47 200 ${\mathrm{cm}}^{\ensuremath{-}1}$ (2120 \AA{}) in Ca${\mathrm{F}}_{2}$ and 46 900 ${\mathrm{cm}}^{\ensuremath{-}1}$ (2135 \AA{}) in La${\mathrm{F}}_{3}$. The identification of this peak as a transition to the $^{1}S_{0}$ level rather than as part of the $4f\ensuremath{\rightarrow}5d$ transition is based on its small spectral shift when observed in different environments, its low intensity, and its relatively narrow width---all of which are characteristics of a shielded $4f$ transition.