Stimulated excited-state Raman scattering and three-photon scattering in sodium

Abstract
We have observed stimulated emission from Na vapor excited by a laser tuned near the Na D lines. The stimulated-emission processes have been identified as Rayleigh scattering, excited-state Raman scattering, and ordinary as well as resonance-enhanced three-photon scattering. The observations indicate that at least part of the conical emission observed in many systems has its origin in these processes.