By means of the coherent states technique the interaction of local modes of imperfections in alkali halide crystals with charged particles emerging from an ion avalanche is investigated. The energy obtained by an imperfection and that lost by a particle on unit way due to the interaction are evaluated. Part of the excess energy of the mode relaxes through phonon processes, a smaller part of the energy is emitted by the crystal on the local mode frequency. This way during the interaction the local mode emits infrared radiation; an estimate is given concerning the intensity of this radiation. This intensity has a well-defined peak at the velocity of particles being in resonance with the local mode frequency. Using different local centres some information can be obtained about the velocity distribution of particles inside the crystal during irradiation.