f-f and f-d transition interference in Sm2+:SrFCl

The 5D3(4f6)-7F0(4f6) transition of Sm2+ in SrFCl is found to be anomalously strong and it exhibits an asymmetric line shape, which is interpreted in terms of resonant interaction between the 5D3 excited state and the vibronic levels of a low-lying 4f55d electronic state. The electronic coupling strength is estimated to be of the order of 100 cm-1. The symmetry species of interacting levels are identified, and the possibility of an E×(b1+b2) type of Jahn-Teller effect in the 4f55d state is discussed