Three-photon magnetoabsorption of excitons in alkali halides.

Abstract

Three-photon magnetoabsorption measurements in fields up to 9 T are presented for the first time. A narrow exciton line of ${\ensuremath{\Gamma}}_{5}^{\ensuremath{-}}$ symmetry is resolved in CsI at 5.8076 eV. A $g$ value of 1.17 is deduced from the Zeeman splitting of this exciton. At high magnetic fields an exciton of ${\ensuremath{\Gamma}}_{3}^{\ensuremath{-}}$ symmetry is detected. The analysis of the field-dependent mixing of the ${\ensuremath{\Gamma}}_{3}^{\ensuremath{-}}$ and ${\ensuremath{\Gamma}}_{5}^{\ensuremath{-}}$ excitons yields a zero-field shift of the ${\ensuremath{\Gamma}}_{3}^{\ensuremath{-}}$ exciton to lower energies of 0.54 meV and an effective $g$ value for the admixture of 1.20.