The absorption and magnetic circular dichroism of spectra of Cs2NaPrCl6

Abstract

The room temperature absorption and magnetic circular dichroism spectra and the absorption spectrum at liquid helium (liquid He) temperature have been measured for Cs₂NaPrCl₆. At room temperature the crystal is cubic and the Pr³⁺ sites have O _h symmetry. All terms above 15 000 cm^-1, except ¹S₀, have been assigned and a previous assignment in PrCl₆ ^3- has been shown to be incorrect. The transition at 20 631 cm^-1 is assigned to ³H₄(A _1g ) →³P₁(T _1g ), in contradiction to previous assignments of Pr³⁺ spectra in other systems. A rich vibrational structure was observed in every transition. Vibrations have been assigned using the site group approximation and there is substantial agreement with the vibrational assignments in Cs₂NaEuCl₆. A crystal phase transition takes place between room temperature and liquid nitrogen temperature and the O _h forbidden transitions, A _1g →E_g and T _2g , are observed. At lower temperatures many additional lines are observed but it is unclear presently whether they are due to lower symmetry or a breakdown of the site group approximation.