Title: The baric changes of the refractive properties of K₂SO₄ crystals
Author(s):

	V.Yo.Stadnyk (Franko Lviv National University, Kyrylo and Mefodij, 8Str., Lviv, 79005 Ukraine) ,
	M.O.Romanyuk (Franko Lviv National University, Kyrylo and Mefodij, 8Str., Lviv, 79005 Ukraine) ,
	O.Z.Chyzh (Franko Lviv National University, Kyrylo and Mefodij, 8Str., Lviv, 79005 Ukraine) ,
	V.F.Vachulovych (Franko Lviv National University, Kyrylo and Mefodij, 8Str., Lviv, 79005 Ukraine)

The dependencies of the birefringence Δn_i of K₂SO₄ crystals in wide spectral (250-800 nm) ranges, as well as the effect of uniaxial mechanical stresses on them have been studied. The values of n_i for K₂SO₄ are found to be rather sensitive to the uniaxial stress. The spectral characteristics of the refractive indices n_i of free and mechanically clamped K₂SO₄ crystals have been studied. The refractive indices turned out to decrease under the effect of uniaxial stress. The variations in the refraction, electron polarizability and the position of the center of the effective ultraviolet absorption band have been calculated. It is shown that the positions of the isotropic points in these crystals can be controlled by thermal and spectral methods.}

Key words: bireringence, refractive indices, uniaxial pressure, phase transition, isotropic state, structure, energy band
PACS: 71.20.Ps, 78.20.Ci