Beschreibung:
<jats:title>Abstract</jats:title><jats:p>The luminescence emission of CdS single crystals is investigated in the exciton spectral region for high one‐photon and two‐photon excitation at 1.8 K. The inelastic scattering of two excitons (P‐line) is resolved into three distinct lines, corresponding to the transition of one exciton from the 1s state into the states 2p, 3p, and <jats:italic>n</jats:italic> = ∞. The latter transition leads to photoconduction. The lines M and P<jats:sub>M</jats:sub>, discovered by Shionoya et al. and ascribed by him to the recombination and inelastic scattering of exciton molecules, are interpreted as Stokes acoustical phonon wings of the exciton–impurity complex lines I<jats:sub>2</jats:sub> and I<jats:sub>1</jats:sub>. The M and P<jats:sub>M</jats:sub>‐lines are stimulated at high intensities. The onset of several laser modes is observed for the P<jats:sub>M</jats:sub>‐line. The mechanism of this two‐boson (photon and acoustic phonon) laser is discussed.</jats:p>