Temperature dependence of overtone intensity in raman scattering by liquids

A polyene chain of canthaxanthin investigated by temperature-dependent resonance Raman spectra and density functional theory (DFT) calculations

“…In our observed case for canthaxanthin as a similar carotenoid, it is reasonable to conclude that the λ strengthening as a candidate factor interprets the fact that the CC overtone/combination relative to the fundamentals increases with temperature decreasing. Secondly, the Boltzmann distribution of a set of molecules at vibrational levels υ j gives the following relationships between the intensity and temperature for Stokes Raman lines: [26] for a fundamental…”

“…( 7) using I data at the liquid-vapor transition, and show that they are in good agreement, which indicates that equation ( 7) is correct. [26] It enables us to predict the following features of the T dependence: negative dI/dT for all Stokes lines, since the exp(U op /kT ) factor decreases more rapidly than the second factor [1 − exp(−1.44υ j /T )] −1 in Eq. ( 7) increases.…”