Relaxation of the 2s Hot Excitons in Alkali Iodides

In the 2s exciton absorption region, remarkable oscillation structures with the energy interval of the LO phonon have been observed on the luminescence excitation spectra. The oscillation structures for 1s free exciton luminescence, E x luminescence and impurity luminescence are in phase with one another, and the structures for σ luminescence and π luminescence are also in phase with each other. The structure for the former group is, however, out of phase with the structure for the latter group. These two series of the oscillation structures are discussed by introducing several relaxation processes of 2s hot excitons, such as cascade relaxation, self-trapping and interband scattering, and the rates of the processes are estimated.