Temperature dependence of Coherent versus spontaneous Raman Scattering

TL;DR

This paper compares coherent and spontaneous Raman scattering for thermometry, showing that quantum interference reduces sensitivity in coherent methods but that anharmonic vibrational features can restore temperature measurement capabilities.

Contribution

It reveals how quantum interference affects coherent Raman thermometry and proposes using anharmonic vibrational signatures to improve temperature sensitivity.

Findings

Quantum interference reduces thermal sensitivity in coherent Raman scattering.

Harmonic vibrations show null sensitivity to temperature changes.

Vibrational hot bands enable effective coherent Raman thermometry.

Abstract

Due to their sub picosecond temporal resolution, coherent Raman spectroscopies have been proposed as a viable extension of Spontaneous Raman (SR) thermometry, to determine dynamics of mode specific vibrational energy content during out of equilibrium molecular processes. Here we show that the presence of multiple laser fields stimulating the vibrational coherences introduces additional quantum pathways, resulting in destructive interference. This ultimately reduces the thermal sensitivity of single spectral lines, nullifying it for harmonic vibrations and temperature independent polarizability. We demonstrate how harnessing anharmonic signatures such as vibrational hot bands enables coherent Raman thermometry.