Thomson-resonant interference effects in quasielastic x-ray Raman scattering near the Cl K edge of HCl*

Quasielastic x-ray Raman scattering is investigated experimentally and theoretically around the Cl K edge of HCl. Strong interference effects between Thomson scattering and resonant scattering are observed throughout the near-threshold region, where the Thomson and resonant scattering contributions are found to be of comparable strength, a result in contrast to the conventional wisdom about the importance of nonresonant scattering. The results also exhibit strong polarization sensitivity, allowing easy identification of interferences between resonant and nonresonant channels.