Paramagnetism of caesium titanium alum

Caesium titanium alum, CsTi(SO4)2⋅12H2O, is a β alum and exhibits a large trigonal field and a dynamic Jahn–Teller effect. Exact calculations of the linear 2T2⊗e Jahn–Teller coupling show that in the strict S6 site symmetry the ground multiplet consists of a Kramers doublet 2Γ6 with magnetic splitting factors g∥=1.1 and g⊥=0, a Γ4Γ5 doublet at ∼60 cm−1 with g∥=2.51 and g⊥=0.06 and another Γ4Γ5 doublet at ∼270 cm−1 with g∥=1.67 and g⊥=1.83. The controversial g values observed below 4.2 K, g∥=1.25 and g⊥=1.14, are shown to arise from low symmetry distortions. These distortions couple the vibronic levels and induce into the ground state the off-diagonal axial Zeeman interaction that exists between the first excited and the ground vibronic levels.