Fine structures in Optical Absorption Spectra of MnO

Absorption spectra of MnO single crystals are measured at various temperatures. Four broad absorption bands are observed in the visible and near-ultraviolet regions. Fine structures in A, C and D bands are found at low temperatures for the first time. Tentative assignments or these fine structures are made based on the combinations of three kinds of elementary excitations (i.e. exciton, magnon and phonon (\(\))). Obtained results are all in good agreement with the measured values. The Racah parameters B and C, the crystal-field strength Dq and the covalency parameter ε are determined to be 560 cm -1 , 3640 cm -1 , 1086 cm -1 and 0.02, respectively, from the fitting procedure of the observed band positions.