ENERGY-LEVELS OF 2-DIMENSIONAL ANISOTROPIC EXCITONS

Calculations are presented towards determining if direct transitions away from the gamma point can give rise to resonant enhancement of Raman scattering observed in InSe. The exciton acting as the intermediate scattering state for this transition may be charecterized by its mass anisotropy in the plane of an InSe layer. The Rayleigh-Ritz variational method has been used to calculate the energy levels of the effective mass Hamiltonian for values of the mass ratio, m(y)/m(x), ranging from 1 to 40. We have also used perturbation theory to calculate the energy levels of the effective mass Hamiltonian in the nearly isotropic limit. Good agreement is found between this method and the variational calculation for mass ratios m(y)/m(x) < 1.5.