An analysis of Yb3+ spectra in YAG in terms of the splitting of the ze
ro-phonon lines in the case of near resonance between Stark levels and
sharp peaks in the phonon spectrum is presented. The theoretical rela
tions allow estimation of the position of the electronic level and vib
ronic coupling strength from the intensity ratio and spectral shifts.
A new energy level scheme for the F-2(5/2) Yb3+ multiplet in YAG is pr
oposed. (C) 1998 Elsevier Science S.A.