Confirmation of the red band system in MnO₄^-as¹T₁←¹A₁from the effect of pressure on single crystal absorption spectra

Abstract

The application of uniaxial pressure to single crystals of LiClO4 . 3H2O/LiMnO4. 3H2O and Ba(ClO4)2. 3H2O/Ba(MnO4)2. 3H2O has led to a large splitting of the zerophonon origin line at 13 772 cm-1 in the absorption spectrum of the lithium salt and a much smaller splitting of the 14 247 cm-1 line in the corresponding spectrum of the barium salt. Furthermore, a third line at ∼ 13 764 cm-1 appears in the spectrum of the lithium salt at high pressures. The polarization behaviour of the three lines from the lithium salt is exactly as would be expected for a forbidden electric-dipole 1 T 1 ← 1 A 1 transition in the parent tetrahedral point group.