Abstract
The optical properties of Wannier excitons interacting with LO phonons are discussed in terms of the oscillator strengths and optical-absorption coefficients. The quantities were calculated for the zero-phonon line and their phonon side bands in single-photon absorption as well as two-photon absorption. General properties of the optical spectra are described for the ground state and the first excited states. Numerical results for the cuprous halides and cuprous oxide compare satisfactorily with experimental data.