抄録
Internal energy-levels of Wannier excitons in anisotropic crystals are treated in the case in which the anisotropy of the product εjμj is small, where εj and μj are the components of the dielectric constant of the crystal and the reduced effective-mass of the exciton, respectively, along the j-th axis. When this product is isotropic, exciton levels are hydrogenic. Typical combinations of anisotropies of electron and hole effective-masses which make εjμj isotropic are briefly examined. In the case of weak anisotropy in εjμj, shifts of exciton energy-levels from hydrogenic ones and removals of their degeneracies are studied by using a perturbation method and introducing new anisotropy parameters. The expressions of the energy corrections for low-lying levels of the excitons are obtained.
