Low-energy optical absorption in ReO3

The absorptivity of polycrystalline samples of ReO₃ has been measured in the range 0.11 to 2.8 eV using a calorimetric technique. New structures have been found in the absorptivity, appearing at about 0.4 and 1.0 eV. The data have been Kramers-Kronig analyzed to obtain the optical constants. Band-calculation results of Mattheiss are presented and a tentative identification of the origin of the new structures is made. A comparison of the present data with those of Feinleib, Scouler, and Ferretti is made.