Study of resonance Raman cross section of aqueous β -carotene at low concentrations

Abstract

Applying Teflon-AF waveguide cell, we determined the absolute resonance Raman cross sections (RCS) for C=C and C-C stretching modes of β-carotene in aqueous solution at low concentrations (10-6–10-10 M) by measuring Raman intensity. It was unexpected that the RCS increased rapidly with the decrease of concentration at extremely low concentration range (10-8–10-10 M), and it reached the value of 1.22×10-21 cm2 molecule-1Sr-1 at 2.5×10-10 M larger than general RCS (10-30 cm2 molecule-1Sr-1) for 109 times. Additionally, we give the tentative theory exploration for the experimental results that the large RCSs at low concentrations attributed to both resonance Raman effect and dipole-induced dipole interactions between solute and solvent molecules.