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).