Absorption spectrum of the Mn2+ ions in crystals of lanthanum manganese double nitrate and praseodymium manganese double nitrate

The optical absorption spectrum of the Mn²⁺ ions in the two double nitrates La₂Mn₃(NO₃)₁₂ ? 24H₂O and Pr₂Mn₃(NO₃)₁₂ ? 24H₂O were measured up to 30000 cm^?1. Uniaxial stress was applied to the crystals to determine the multiplicity of the observed zero phonon lines belonging to the transitions from the groundstate⁶ A ₁ (⁶ S) to the excited states⁴ E(⁴ G) and⁴ T ₂(⁴ D). The Zeeman effect of the states⁴ A ₁(⁴ G) and⁴ E(⁴ G) was measured with magnetic fields up to 6.4T. The effect of covalency and trigonal field, especially to the states⁴ A ₁ (⁴ G) and⁴ E(⁴ G), is briefly discussed.