Enhancement of the Raman Effect by Infrared Pumping

TL;DR

This paper introduces a novel technique to significantly enhance Raman scattering by using infrared pumping to coherently excite molecular vibrations, resulting in a substantial increase in signal strength.

Contribution

The authors propose a new method employing IR radiation at half the Stokes shift to coherently excite molecules, boosting Raman signals by up to four orders of magnitude.

Findings

Raman scattering can be increased by up to 10,000 times.

Infrared pumping induces coherent nuclear oscillations via Fröhlich coupling.

The method enhances Raman signals proportionally to the square of the number of molecules.

Abstract

We propose a method for increasing the Raman scattering from an ensemble of molecules by up to four orders of magnitude. Our method requires an additional coherent source of IR radiation with the half-frequency of the Stokes shift. This radiation excites the molecule electronic subsystem that in turn, via Fr\"ohlich coupling, parametrically excites nuclear oscillations at a resonant frequency. This motion is coherent and leads to a boost of the Raman signal in comparison to the spontaneous signal because its intensity is proportional to the squared number of molecules in the illuminated volume.