Light scattering and absorption by fractal-like carbonaceous chain aggregates: comparison of theories and experiment.
نویسندگان
چکیده
This study compares the optical coefficients of size-selected soot particles measured at a wavelength of 870 nm with those predicted by three theories, namely, Rayleigh-Debye-Gans (RDG) approximation, volume-equivalent Mie theory, and integral equation formulation for scattering (IEFS). Soot particles, produced by a premixed ethene flame, were size-selected using two differential mobility analyzers in series, and their scattering and absorption coefficients were measured with nephelometry and photoacoustic spectroscopy. Scanning electron microscopy and image processing techniques were used for the parameterization of the structural properties of the fractal-like soot aggregates. The aggregate structural parameters were used to evaluate the predictions of the optical coefficients based on the three light-scattering and absorption theories. Our results show that the RDG approximation agrees within 10% with the experimental results and the exact electromagnetic calculations of the IEFS theory. Volume-equivalent Mie theory overpredicts the experimental scattering coefficient by a factor of approximately 3.2. The optical coefficients predicted by the RDG approximation showed pronounced sensitivity to changes in monomer mean diameter, the count median diameter of the aggregates, and the geometric standard deviation of the aggregate number size distribution.
منابع مشابه
Light Scattering by Fractal Aggregates: A Review
This paperpresents areviewof scatteringandabsorptionof light by fractal aggregates. The aggregates are typically diffusion limited cluster aggregates (DLCA) with fractal dimensions of D ’ 1:75, which occur frequently in aerosols and colloids, but other types of aggregates are discussed as well. The results of the review are quite general. A scaling description of the scattering of waves forms t...
متن کاملFractal Analysis of Aggregates Formed Scattering Methods by HeatingDilute BSA Solutions Using Light
of pH 5.1 to O.1% and O.OOI% solutiens, respectively, and heated at 950C, yarying the heating time t.. The fractal dimension Df of the aggregate in the solution was evaluated from static light scattering experiments. The polydispersity exponent t and the average hydrodynamic radius of the aggregates were calculated from dynamic light scattering experiments using master curves obtained by K...
متن کاملDetermination of branch fraction and minimum dimension of mass-fractal aggregates.
Particles of micrometer to nanometer size often aggregate to form branched structures. Such materials include metals and metal oxides as well as biological and polymeric materials (considering the persistence length as a primary unit). Characterization of such structures is difficult since they typically display disordered, irregular features in three dimensions. Branched aggregates display two...
متن کاملAbsorption and scattering by fractal aggregates and by their equivalent coated spheres
This paper demonstrates that the absorption and scattering cross-sections and the asymmetry factor of randomly oriented fractal aggregates of spherical monomers can be rapidly estimated as those of coated spheres with equivalent volume and average projected area. This was established for fractal aggregates with fractal dimension ranging from 2.0 to 3.0 and composed of up to 1000 monodisperse or...
متن کاملForward-Light-Scattering Characterization of Pre-Crystalline Aggregates in Crystallizing Lysozyme Solutions
We present a method to characterize lysozyme pre-crystalline aggregates using a forward-lightscattering technique, which is highly sensitive to protein aggregates. The static light scattering properties at small angles of crystallizing lysozyme aggregates are discussed, and related to the crystallization conditions based on the concentration of added precipitant NaCl. Lysozyme solutions that st...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Applied optics
دوره 46 28 شماره
صفحات -
تاریخ انتشار 2007