THE ANISOTROPY OF THE INTENSITY OF THE OPTICAL-ABSORPTION IN BETA'-TB-2(MOO4)(3)

Optical absorption spectra were measured in polarized light in a metas table orthorhombic ferroelectric beta'-phase of Tb-2(MoO4)(3) at 7 K. Measurements were made at four directions of the wave vector (k) over bar along the crystal axes [100], [1(1) over bar0$], [001] and [001]. For all these directions of (k) over bar the measurements were perform ed at two mutually perpendicular directions of the electric vector of light I along the principal crystal axes perpendicular to (k) over bar . 14 absorption peaks were observed with the wave numbers from 20520 c m(-1) to 20655 cm(-1). They correspond to the dipole-forbidden transit ions F-7(6)-D-5(4) in Tb3+-ions. A strong anisotropy of the absorption was observed. Using the anisotropy of the absorption it was shown, th at the main contributions to the intensities of the observed absorptio n peaks were due to the electric-quadrupole transitions to the excited states of Gamma(1)-symmetry.