Spontaneous Raman scattering by ground-state oxygen atoms

Abstract

We report the first known observation of Raman scattering by oxygen atoms. The ³P₂ →³P₁ and ³P₂ →³P₀ transitions in the electronic ground state that produced Raman shifts of 158 and 227 cm⁻¹ were detected. These transitions were observed in a fuel-lean atmospheric H₂ + O₂ flame. By comparing the O electronic and O₂ pure-rotational Raman-scattering intensities, we measured the polarized cross sections for the two lines to be 6 ± 1 × 10⁻³¹ and 4 ± 1 × 10⁻³¹ cm²/sr, respectively, with an excitation source at 532.1 nm. These cross sections are two to three times stronger than those predicted by a single-configuration single-excitation Coulomb approximation.