Pseudo-Stark splitting induced by a phase transition in the optical spectra of ferroelectrics with dipole impurity centers
Basun S. A., Kaplyanskii A. A., Feofilov S. P.
A splitting of R lines has been observed in the course of the D2h -> C2v phase transition in Li2Ge7Ol5:Cr3+ crystals. This splitting indicates that the ensemble of Cr3+ centers of the paraelectric phase splits into two physically nonequivalent ensembles in the course of the transition to the ferroelectric phase. This effect stems from the triclinic local symmetry of the Cr3 + centers, which have a dipole moment. The splitting of the R lines is a "pseudo-Stark" splitting in the odd internal crystal field induced in the ferroelectric phase by a polar order parameter.
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![](/ps/1281/article_19376_800_head.png "A splitting of <i>R </i>lines has been observed in the course of the <i>D<sub>2h</sub> -> C<sub>2v</sub> </i>phase transition in Li<sub>2</sub>Ge<sub>7</sub>O<sub>l5</sub>:Cr<sup>3+</sup> crystals. This splitting indicates that the ensemble of Cr<sup>3+</sup> centers of the paraelectric phase splits into two physically nonequivalent ensembles in the course of the transition to the ferroelectric phase. This effect stems from the triclinic local symmetry of the Cr<sup>3</sup> <sup>+</sup> centers, which have a dipole moment. The splitting of the <i>R </i>lines is a "pseudo-Stark" splitting in the odd internal crystal field induced in the ferroelectric phase by a polar order parameter.")