3. Theory
In a cubic crystalline field of low to moderate strength, the five d electrons of Mn2+ ion are distributed in the t2g and eg orbitals, with three in the former and two in the latter orbitals. Thus, its ground state configuration is (t2g) 3 (eg) 2. This configuration yields to energy levels such as 6 A1g, 4 A1g, 4 Eg, 4 T1g, 4 T2g and to a number of doublet states of which 6
A1g lies lowest according to Hund’s rule. The free ion levels of