Absolute Stimulated Raman Cross Sections of Molecules

Stimulated Raman scattering (SRS) is a fundamental opticalprocessthat was discovered more than 60 years ago. While the early SRS spectroscopystudies have provided valuable insights into materials systems, theadvent of SRS microscopy has launched a rapidly growing field in biologicalimaging. However, a fundamental understanding of the molecular responseunder SRS is still lacking. Herein we present a new framework to introducemolecule-intrinsic stimulated Raman scattering cross sections, & sigma;(SRS), in the unit of Go''ppert-Mayer (GM). The absoluteSRS cross sections determined for real molecular systems challengethe conventional wisdom that Raman spectroscopy is always a weak process.The enormous rate acceleration of SRS, captured by an apparent SRScross section, stems from a synergistic effect between the field andthe molecule. Our new framework goes beyond the conventional optics-centricview and presents a molecule-inclusive perspective, thus offeringa comprehensive foundation for the future growth of SRS spectroscopyand microscopy.

Automated summary

Stimulated Raman scattering (SRS) is a fundamental optical process that has been known for over 60 years. While SRS microscopy has advanced biological imaging, there is still a lack of understanding of the molecular response under SRS. This study introduces a new framework to determine the molecule-intrinsic SRS cross sections and challenges the conventional belief that Raman spectroscopy is always a weak process. The findings provide a comprehensive foundation for future advancements in SRS spectroscopy and microscopy.