The probability of bi‐exciton formation in crystals

Abstract In first order of perturbation theory the probability of binding of two excitons into a bi‐exciton accompanied by light emission and caused by exciton–exciton collisions is calculated. Firstly the case is considered where two excitons of 1s‐type and n‐p‐type form a bi‐exciton in the ground state consisting of two excitons of 1s‐type. The binding is accompanied by light emission. The luminescence begins with a threshold and the luminescence band has the form of a sharp asymmetrical peak. The exciton–exciton collisions lead to the binding of two excitons of 1s‐type with no internal excitation. Numerical estimations of the processes under consideration are made for a set of crystals.