Redistributed spectrum of scattered light

The spectrum of redistributed light that results from excitation by monochromatic near-resonant incident light has been observed in calcium perturbed by argon. The two components were found to be well described by the astrophysical redistribution functions ${\mathit{R}}_{\mathrm{II}}$ and ${\mathit{R}}_{\mathrm{III}}$ for the Rayleigh and fluorescent peaks, respectively. The Doppler width of the Rayleigh component was observed to be √2 larger than that of the fluorescent component, for our observation at right angle to the incident beam, clearly demonstrating the coherence of this part of the scattering. The ratio of fluorescent to Rayleigh intensity was independent of detuning within our range, which was well within the impact region, and increased linearly with argon pressure in a manner that is consistent with an identification of the cross section for redistributing collisions with that for line broadening.