Observation of Resonance Raman Scattering below the Dissociation Limit inI2Vapor

Inelastic photon scattering from ${\mathrm{I}}_2$ vapor was observed to change from resonance Raman scattering to resonance fluorescence as a single-mode argon laser was tuned through the 5145-Å gain profile. 3 orders of magnitude enhancement in the Stokes and the first-overtone intensities were measured in going from resonance Raman scattering to resonance fluorescence. The intensity distribution of the first 47 overtones is shown for the laser frequency coincident with the $43\to 0 P\left(12\right)\mathrm{}$ and $43\to 0 R\left(14\right)\mathrm{}$ transitions of $B^3\Pi _{0\mathrm{u}}^{}{}_{}{}^{+}\to X^1\Sigma _{0\mathrm{g}}^{}{}_{}{}^{+}$. The resonance Raman cross section of ${\mathrm{I}}_2$ compared with ${\mathrm{N}}_2$ was found to be 2.6 × ${10}^6$.