Mechanism of additional losses of the emitted light in optically anisotropic scintillators like lead tungstate

Unusual decrease of the light yield of scintillations in lead tungstate (PWO) proportional to the logarithm of the length of the crystals is explained by the excitation of the localized surface light waves during the internal total reflection at PWO faces. These light waves are excited due to partial transfer of the light flow from the ordinary normal wave to the extraordinary one with less refractive index. The absorption and scattering of the surface waves by the subsurface defects induce the total losses of the emitted light.