Light scattering

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

Synthesis and optical properties of silver nanobars and nanorice.

Abstract: Silver nanobars with rectangular side facets and an average aspect ratio of 2.7 have been synthesized by modifying the concentration of bromide added to a polyol synthesis. Subsequent rounding of nanobars transformed them into nanorice. Due to their anisotropy, nanobars and nanorice exhibit two plasmon resonance peaks, scattering light both in the visible and in the near-infrared regions. With a combination of discrete-dipole approximation calculations and single-nanoparticle spectroscopy, we explored the effect of nanostructure aspect ratio and corner sharpness on the frequency of plasmon resonance. Near-field calculations and surface-enhanced Raman scattering measurements on single particles were performed to show how local field enhancement changes with both the wavelength and polarization of incident light.

Unsupervised classification of scattering behavior using radar polarimetry data

Abstract: The use of an imaging radar polarimeter data for unsupervised classification of scattering behavior is described by comparing the polarization properties of each pixel in an image to that of simple classes of scattering such as even number of reflections, odd number of reflections, and diffuse scattering. For example, when this algorithm is applied to data acquired over the San Francisco Bay area in California, it classifies scattering by the ocean as being similar to that predicted by the class of odd number of reflections, scattering by the urban area as being similar to that predicted by the class of even number of reflections, and scattering by the Golden Gate Park as being similar to that predicted by the diffuse scattering class. It also classifies the scattering by a lighthouse in the ocean and boats on the ocean surface as being similar to that predicted by the even number of reflections class, making it easy to identify these objects against the background of the surrounding ocean. >

Dependence of the enhanced optical scattering efficiency relative to that of absorption for gold metal nanorods on aspect ratio, size, end-cap shape,and medium refractive index

Abstract: The current intense interest in the properties of plasmonic nanostructures for their applications in chemical and biochemical sensors, medical diagnostics and therapeutics, and biological imaging is fundamentally based on their enhanced optical absorption and scattering properties. In this study, the optical extinction, absorption, and scattering efficiencies were calculated as a function of shape definition, aspect ratio, surrounding medium, and material selection. The discrete dipole approximation method was used, which is known to be a very useful and versatile computational tool for particles with any arbitrary shape. Relative contribution of scattering to the total extinction for the longitudinal mode was found to be significantly dependent on the aspect ratio of the nanorod in a somewhat complex manner, different from a typical linear relationship for the resonance wavelength. A slight elongation of Au nanosphere gives rise to a drastic increase in the relative scattering efficiency, which eventually reaches a maximum and begins to decrease with further increase in the aspect ratio. This is ascribed to the increasing absorptive contribution from the larger imaginary dielectric function of the metal particle in the longer wavelength region where the red-shifted excitation of the longitudinal resonance mode occurs. For transverse mode exhibiting the blue-shift in the resonance peak, on the contrary, the absorption efficiency is relatively enhanced compared to the scattering efficiency with increasing aspect ratio. This is thought to result from the dominant effect of the interband transition present in this wavelength region. Besides the dependence of plasmonic characteristics on the aspect ratio of nanorod, the DDA results for a small change of the end-cap shape and the index of the surrounding medium lead us to conclude that there exist two competing key factors: a weighting factor assigned to the shape parameter and the dielectric function of the metal particle, which control the relative enhancement in the scattering and absorption as well as the linearity of resonance wavelength with regard to the aspect ratio.

Scattering of electromagnetic waves

Abstract: This chapter discusses the scattering of electromagnetic waves. Scattering is due to the change in the motion of the charges in the medium under the influence of the field of the incident wave, resulting in the emission of the scattered waves. The basic scattering process consists in the absorption of the original quantum by the scattering system and the simultaneous emission by that system of another quantum. The frequency of the scattered quantum may be either less or greater; these two cases are called Stokes scattering and anti-Stokes scattering, respectively. In the former case, the system absorbs an amount of energy; in the latter case, it emits energy and makes a transition to a state of lower energy. In the simple case of a gas, scattering takes place at individual molecules and the change in frequency may be due to either a transition of the molecule to another energy level or to a change in the kinetic energy of its motion. Two types of scattering can be distinguished, depending on the change in frequency of the light: (1) Raman scattering and (2) Rayleigh scattering. Raman scattering in gases results from a change, due to the incident light, in the vibrational, rotational, or electronic state of the molecule. Rayleigh scattering, on the other hand, does not involve a change in the internal state of the molecule.