Impurity combinational absorption of a multiphoton field in a dispersive medium

It is shown that the absorption of one field quantum by an impurity atom in a dispersive medium stimulates transitions of the two quanta between different branches of the energy spectrum. The wave vectors of the quanta do not change in this process.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 78–82, February, 1986.