Langmuir mechanism of low-frequency stimulated Raman scattering on nanoscale objects

TL;DR

This paper proposes a Langmuir-like physical mechanism for low-frequency stimulated Raman scattering on nanoscale objects in water, supported by experiments with viruses and nanoparticles, revealing potential for selective virus heating.

Contribution

It introduces a novel Langmuir mechanism based on dipole interactions for stimulated Raman scattering on nanoscale objects, supported by experimental validation.

Findings

Stimulated spectral lines explained by the proposed mechanism

Absence of lower frequency lines and pH-dependent line shifts observed

Microwave radiation can induce local heating of nanoscale objects

Abstract

A simple physical mechanism of stimulated light scattering on nanoscale objects in water suspension similar to Langmuir waves mechanism in plasma is proposed. The proposed mechanism is based on a dipole interaction between the light wave and the non-compensated electrical charge that inevitably exists on a nanoscale object (a virus or a nanoparticle) in water environment. The experimental data for tobacco mosaic virus and polystyrene nanospheres are presented to support the suggested physical mechanism. It has been demonstrated that stimulated amplification spectral line frequencies observed experimentally are well explained by the suggested mechanism. In particular, the absence of lower frequency lines and the generation lines shift when changing the pH are due to ion friction appearing in the ionic solution environment. The selection rules observed experimentally also confirm the dipole interaction type. It has been shown that microwave radiation on nanoscale object acoustic vibrations frequency should appear under such scattering conditions. We demonstrate that such conditions also allow for local selective heating of nanoscale objects by dozens to hundreds degrees K. This effect is controlled by the optical irradiation parameters and can be used for affecting selectively certain types of viruses.