Raman Scattering From Water Vapor

Raman scattering from water vapor has been observed using a thermally-tuned TEM₀₀ ruby laser as excitation for a range of incident wavelengths from 6943.1 Å to 6944 Å covering the strong water absorption line centered at 6943.8 Å with a linewidth of 0.04 Å. Raman scattering cross-section relative to nitrogen has been determined (for the first time to our knowledge) to be 0.39±0.12. No significant enhancement of Raman signal was observed even though the incident ruby was tuned to the absorption line. Possible reasons for the lack of resonance Raman effect are given.