Silver impurities in cubic metal fluorides: Jahn-Teller effects in the 4d⁹5s1 and 4d⁹ multiplets

Silver was introduced into several metal fluorides with the aim to generate different Jahn-Teller (JT) situations. Optical absorption and luminescence experiments involving the ground 4d¹⁰ апd the excited 4d⁹5s¹ configuration of Ag⁺ revealed a weak T ⊗ e JT effect in the (approximately) T₂ excited triplets in NaF and SrF₂, but much stronger differences between different hosts in the (approx.) E doublet. The strongest effect was observed in the host NaF. The theoretical developments initiated by Wagner have given the best interpretation of the observed temperature dependence of optical line shapes. EPR experiments (in part with a sample under uniaxial stress) on Ag²⁺ in MeF2 crystals (Me: Ca, Sr, Ba) and SrCl₂ demonstrated the action of a T₂ ⊗ t₂ JT effect for the former two hosts and, probably, a quadratic JT effect or an off-centre situation for the latter two. The experimental results and models are presented.