We report transmittance and polarized reflectance measurements of crystalline ${\mathrm{Mn}}_{12}$-acetate over a wide frequency range (600–50 000 ${\mathrm{cm}}^{-1})$ to investigate the electronic structure of this prototypical molecular magnet. Overall, the spectral features are quite diffuse down to 10 K, although a number of Mn inner $\to$ outer and O $\overrightarrow{p}$ Mn d charge transfer excitations are observed and assigned. The two lowest energy excitations (at 13 500 and 15 900 ${\mathrm{cm}}^{-1})$ are polarized perpendicular to the easy magnetization (c) axis. Optical gaps are estimated at 8750 ${\mathrm{cm}}^{-1}$ (1.08 eV) and 14 000 ${\mathrm{cm}}^{-1}$ (1.75 eV), corresponding to minority and majority gaps, respectively.

• Received 21 August 2001

DOI:https://doi.org/10.1103/PhysRevB.65.054419