OPTICAL-ABSORPTION BY IMPURITIES IN SEMICONDUCTORS

Parts of the linear and quadratic coupling of the electron-phonon system are included in a discussion of optical absorption and emission by an electron that is bound to an impurity in a semiconductor and is in interaction with the lattice vibrations. An adiabatic approach is not used. Comparison is made between an approach based on the Bethe-Sommerfeld expression in the representation in which the Hamiltonian is diagonal and one based on a correlation function approach.