The author presents original results on the dynamics of two-electron processes in impurity semiconductors using the Mössbauer spectroscopy method in crystalline and vitreous chalcogenides of lead (PbS, PbSe, PbTe), germanium (Ge - S, Ge -Se) and arsenic (As - S, As - Se, As - Te). The book is addressed to researchers, doctoral students and graduate students specializing in the physics of semiconductors.