Magneto‐Optical Properties of F 2 + Center in KCI:SH −

The magnetic circular dichroism (MCD) of F   2 +centers in KCI:SH − has been measured in absorption in the 1sσ g → 2p y π u transitions at 493 and 509 nm, with fields up to 5 T and in the temperature range 1.5 K < T < 77 K. Within the limit of detection, no MCD is observed in the near infrared transition 1ss̀ g → 2ps̀ u as well as in both emissions 2pσ u → Iss̀ g and 2ps̀ g . The optical detection of EPR in the F   2 +ground state presents an isotropic single band with g = 1.965 ± 0.007. The spin‐lattice relaxation measured at H = 0.32 T is typical of a direct process T −1 = 4.3 × 10 −2 coth ( g μ B H /2 k B T ). The spectral variation of the MCD is calculated using perturbation theory to first order. The Hamiltonian includes the spin‐orbit interaction in the 2pπ u excited state and the orbital molecular wave functions are obtained by a linear combination of 1s and 2p atomic orbitals. The calculated MCD is in good agreement with the observed one, for the spin‐orbit interaction strength σ z = 3.6 meV.