Optical properties of scheelite and raspite<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">PbWO</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>crystals

Reflection spectra of lead tungstate $({\mathrm{PbWO}}_{4})$ crystals with scheelite and raspite structures have been measured at 6 K in the spectral range from 3 to 25 eV. The optical constants of both phases have been derived through the Kramers-Kronig analysis. The absorption spectra thus obtained exhibit a strong doublet exciton structure at around 4.30 eV for the scheelite phase and a weak exciton band at 3.75 eV for the raspite phase. The scheelite sample gives rise to a luminescence band peaking at 2.80 eV, while the raspite sample emits a band at 2.25 eV. The decay behaviors of these bands are found to be similar to each other. The 2.80- and 2.25-eV luminescence bands are intrinsic to the respective phases. The above results are discussed on the bases of a recent band-structure calculation of scheelite ${\mathrm{PbWO}}_{4}$ and of a difference in crystal structure between the two phases. Furthermore, it is suggested that the controversial ``green'' luminescence in scheelite is due to the raspite-type inclusions introduced by thermal stress during the crystal growth.