Table 2.

Selection rules for Cr³⁺ d-d electronic transitions in O_h site symmetry for in Li₃Cr₂(PO₄)₃.

Electronic transition Oh	Electric dipole allowed with Γu vibration $⟨{\mathrm{\Gamma }}_i\left|T_{1u}\right|{\mathrm{\Gamma }}_f⟩{\mathrm{\Gamma }}_u=A_{1g}$
4A2g → 4T2g	a1u, t1u, t2u, eu
4A2g → 4T1g	a2u, t1u, t2u, eu