Low-temperature optical absorption of ferrous fluosilicate crystals

Abstract

The optical spectrum of the Fe²⁺ ion in an electric field of trigonal symmetry has been investigated down to liquid helium temperature. An account is given of the results, which suggest the operation of the dynamic Jahn-Teller effect and reveal the presence of a charge-transfer absorption and the action upon the latter of the low-symmetry component of the electric field. A structure which is present on the low-energy side of the main vibronic band, has been proved to be due to the crystal lattice rather than to the magnetic ions.