Optical absorption of MgO:Mn

Wavelength-modulated absorption measurements on MgO show the presence of Mn3+ and Mn2+. The lowest spin-allowed transition of Mn3+ occurs at 520 nm. Weak bands at 301, 356, 389 and 426 nm are attributed to transitions from 6A1g to the 4T1g(P), 4T2g(D), 4E g(G)+4T2g(G) and 4T2g(G) states of Mn2+, respectively. The latter band shows four zero-phonon lines with an over-all splitting of 34 cm-1 revealing a spin-orbit splitting of the 4T2g(G) state reduced by a factor of four by the action of a dynamic Jahn-Teller effect. Stress experiments indicate that the dominating Jahn-Teller interaction is with T2 symmetry vibrations.