Magnetic Dipole Optical Absorption Spectrum of MnF2

We present quantitative intensity measurements on six magnetic dipole absorption transitions in MnF2 as well as some high-magnetic-field experiments with components of the field along both the c axis and in the basal plane. We interpret these results and those of previous investigators on the T14(I), A14E(I)4, T24(II), and T14(II) states, at first using a crystal-field calculation which ignores the vibronic aspects of the problem. With this calculation we can phenomenologically obtain the low-symmetry-field energy-level scheme and explain the effects of high magnetic fields on the spectrum, but we cannot obtain a consistent set of one-electron low-symmetry-field parameters for all the excited states. By considering the vibronic problem, we find that we can understand all the excited states in a consistent manner, and explain the small spin–orbit coupling in the T14(I) state. In addition, we show that for the nearly degenerate A14E(I)4 states, the A14 state does not lie low.