Experimental Observation of Molecular Rotations Stimulated by Optical Magnetic Forces

Conventionally, the interaction of the magnetic field of light with materials is ignored since most materials have low magnetic susceptibilities. However, in the high field, magneto-electric interactions can cause enhanced magnetic dipole scattering. Enhanced magnetization in homogeneous dielectrics is of fundamental importance to high-frequency magnetism. We report optically induced magnetization and stimulated librations at the molecular level in liquid CCl₄, SiCl₄, Si(OCH₃)₄, and Si(OC₂H₅)₄ and compare results with a quantum theory which analyzes the conversion of orbital angular momentum to molecular rotation via optical magnetic torque[1]. The inter-conversion of angular momenta increases the effective area enclosed by polarization currents governing magnetic response. Our results are the first observations of Stokes-shifted librations and vibrations driven by femtosecond magneto-electric interactions in tetrahalides and strongly support a torque-mediated mechanism.
[1] A. A. Fisher et al., Theory of induced optical magnetism, Optics Express 24, 26055(2016).