Collision-induced optical double resonance

The double-resonance concept is extended to the situation of two coherently driven optical transitions that do not share a common level but are coupled by molecular collisions that tip the angular momentum vector while preserving the molecular velocity and the rotational energy. This collision-induced double resonance is observed as sharp resonances, free of Doppler broadening, and can be explained in the same order of perturbation theory as the ordinary double-resonance experiment. They appear as satellite lines accompanying the usual double resonance or Lamb-dip spectra. © 1974 The American Physical Society.