Refractometry of Mechanically Compressed (NH_(4))_(2)SO_(4) Crystals

摘要

The effect of uniaxial mechanical pressure (sigma)_(m) <= 150 bar on the spectral (300-800 nm) dependence of the birefringerence (DELTA)n_(i) and refractive indices n_(i) of (NH_(4))_(2)SO_(4) crystals has been investigated. It is shown that the dispersion of n_(i)(lambda) and (DELTA)n_(i)(lambda) is normal and sharply increases with approach to the absorption edge. It is established that uniaxial pressure does not change the character of the dispersions dn_(i)/d(lambda) and d(DELTA)n_(i)/d(lambda) and only affects their magnitudes. It is shown that the increase in the refractive indices under uniaxial stress is mainly due to the increase in the refraction caused by the increase in the band gap and long-wavelength shift of the UV absorption band maximum.