Relativistic effects on magnetic circular dichroism studied by GUHF/SECI method

Quasi-relativistic formulation of the Magnetic circular dichroism (MCD) Faraday terms are presented using the generalized unrestricted Hartree–Fock (GUHF)/single excitation configuration interaction (SECI) method combined with the finite perturbation method and applied to the MCD of the three n–σ∗ states (3Q1,3Q0,1Q1) of CH3I. The Faraday B term for the 1Q1 state was 0.1976(Debye)2(Bohr magneton)/(103 cm−1) in the non-relativistic theory, but was dramatically improved by the relativistic effect and became 0.0184 in agreement with the experimental values, 0.014 and 0.0257. This change was mainly due to the one-electron spin–orbit (SO1) term rather than the spin-free relativistic (SFR) and the two-electron spin–orbit (SO2) terms.