Stark effect in optical spectra of CaWO4 : Pr3+

The external electric field effect on the f-f absorption spectra for vaious types of centers in CaWO4 : Pr3+ has been investigated by means of sensitive differential technique which permits studying the Stark splittings 'hidden' in a line width by measuring small changes of an absorption line contour in an electric field. Linear and secondary Stark effects are discovered in spectra of main (tetrahonal) centers. The effect character agrees with the S4 symmetry of main centers and their electron states. The linear Stark effect is discovered in spectra of nontetrahonal centers. Point symmetry of nontetrahonal centres of both C2 and C1 is determined. Values of odd fields produced by ions of a main lattice, by compensator ions and by an external electric field are estimated in an approximation of the point model. The results of the estimations are compared with experimental values of linear and secondary effects in spectra of main and secondary centres