Pseudo-Stark splitting in the spectra of Li2Ge7O15:Cr3+ induced by a ferroelectric phase transition

It was found experimentally that an ensemble of Cr 3+ impurity centers in the D 2h paraelectric phase of Li 2 Ge 7 O 15 became split into two physically inequivalent ensembles on transition to the C 2υ ferroelectric phase. This effect was manifested by a doublet splitting of the R lines of the Cr 3+ centers as a result of cooling of a crystal below T c and it was associated with the low noncentrosymmetric (triclinic C 1 ) symmetry of the centers and also with the permanent dipole moment of these centers. The doublet splitting of the R lines of Cr 3+ as a result of the investigated phase transition was found to be of pseudo-Stark nature and it occurred in an internal odd field induced in the ferroelectric phase by a polar order parameter