Light scattering

About: Light scattering is a research topic. Over the lifetime, 37721 publications have been published within this topic receiving 861581 citations.

Multiple Light Scattering from Disordered Media. The Effect of Brownian Motion of Scatterers

Abstract: We have measured the time autocorrelation function of the light intensity multiply scattered from turbid aqueous suspensions of submicron size polystyrene spheres in directions near backscattering. It is found strongly non-exponential at short times revealing the very fast decay of coherence in extended scattering loops due to the thermal motion of the many spheres involved; the longest living decay time is found remarkably close to the single particle backscattering relaxation time even under conditions of interparticle interactions. These features are only weakly affected by the particular interference effect between time-reversed pairs of loops giving rise to the coherent backscattering enhancement. A simple argument is presented which accounts for these observations.

Applications of Laser Radiation Pressure

Abstract: Use of lasers has revolutionized the study and applications of radiation pressure. Light forces have been achieved which strongly affect the dynamics of individual small particles. It is now possible to optically accelerate, slow, stably trap, and manipulate micrometer-sized dielectric particles and atoms. This leads to a diversity of new scientific and practical applications in fields where small particles play a role, such as light scattering, cloud physics, aerosol science, atomic physics, quantum optics, and high-resolution spectroscopy.

Optical pulling force

Abstract: Theoretical analysis suggests that there exists an optical attractive force capable of “pulling” microparticles towards a light source. This backwards force is generated by using interference to optimize the scattering of light in the forwards direction.

Surface enhanced Raman scattering (SERS) by molecules adsorbed at spherical particles

Abstract: A model for Raman scattering by a molecule adsorbed at the surface of a spherical particle is articulated by treating the molecule as a classical electric dipole. This follows Moskovits’s suggestion [ J. Chem. Phys.69, 4159 ( 1978)] and the experiments by Creighton [ J. Chem. Soc. Faraday Trans. II, 75, 790 ( 1979)] that such a system may exhibit SERS similar to that at roughened electrode surfaces. The molecule is stimulated by a primary field comprised of the incident and near-scattered fields. Emission consists of the dipole field plus a scattered field, each at the shifted frequency. Addition of feedback terms between the dipole and the particle makes only a negligible contribution to the fields. For pyridine adsorbed at the surface of a silver sphere, the 1010-cm−1 band is enhanced by ~106 if the radius is much less than the wavelengths and the excitation wavelength is ~382 nm, a wavelength for which the relative refractive index of silver is close to m=2i. Detailed results are given for the effect, upon the angular distribution and the polarization of the Raman emission, of particle size, distance from the surface, excitation wavelength, and location of the molecule upon the surface. These results simulate those observed at roughened silver electrodes and suggest that the mechanism of SERS at those electrodes may resemble the electromagnetic mechanism elucidated here. We predict that comparable effects should be observed for fluorescent scattering.