Light Scattering By Irregularly Shaped Particles

This volume contains most of the invited papers presented at the International Workshop on Light Scattering by Irregularly Shaped Particles held on June 5-7, 1979. at the State University of New York at Albany (SUNYA). Over seventy participants representing many dis ciplines convened to define some of the ever-increasing number of resonant light-scattering problems associated with particle shape and to relate their most recent investigations in this field. It is obvious from the two introductory papers that an investi gator's primary discipline determines his/her approach to the light scattering problem. The meteorologist, Diran Deirmendjian, advocates an empirical methodology: to model the scattering by atmospheric aerosols, using equivalent spheres as standards, in the most effi cient and simplest manner that is consistent with remote sensing, in situ, and laboratory· data. Because of the almost infinite variety of particle shapes, he questions not only the possibility but even the usefulness of the exact solution of scattering by a totally arbitrary particle. The astrophysicist, J. Mayo Greenberg, is primarily concerned with the information content carried by the scattered light because this radiation is the sole clue to under standing the nature of interstellar dust. What measurements (polar ization, color dependence, etc ••• ) should be made to best determine a given particle characteristic (size, surface roughness, refractive index, etc ••• )? Thus, he considers the physics of the scattering process to be of paramount interest.

This is the next volume in series of Light Scattering Reviews. Volumes 1-5 have already been printed by Springer. The volume is composed of several papers ( usually, 10) of leading researchers in the respective field. The main focus of this book is light scattering, radiative transfer and optics of snow.

This fourth volume of Light Scattering Reviews is composed of three parts. The ?rstpartisconcernedwiththeoreticalandexperimentalstudiesofsinglelightsc- tering by small nonspherical particles. Light scattering by small particles such as, for instance, droplets in the terrestrial clouds is a well understood area of physical optics. On the other hand, exact theoretical calculations of light scattering p- terns for most of nonspherical and irregularly shaped particles can be performed only for the restricted values of the size parameter, which is proportional to the ratio of the characteristic size of the particle to the wavelength?. For the large nonspherical particles, approximations are used (e. g. , ray optics). The exact th- retical techniques such as the T-matrix method cannot be used for extremely large particles, such as those in ice clouds, because then the size parameter in the v- iblex=2?a/???,wherea is the characteristic size (radius for spheres), and the associated numerical codes become unstable and produce wrong answers. Yet another problem is due to the fact that particles in many turbid media (e. g. , dust clouds) cannot be characterized by a single shape. Often, refractive indices also vary. Because of problems with theoretical calculations, experimental (i. e. , la- ratory) investigations are important for the characterization and understanding of the optical properties of such types of particles. The ?rst paper in this volume, written by B. Gustafson, is aimed at the descr- tionofscaledanalogueexperimentsinelectromagneticscattering.

Light scattering review (vol 8) is aimed at the presentation of recent advances in radiative transfer and light scattering optics. The topics to be covered include: scattering of light by irregularly shaped particles suspended in atmosphere (dust, ice crystals), light scattering by particles much larger as compared the wavelength of incident radiation, atmospheric radiative forcing, astrophysical radiative transfer, radiative transfer and optical imaging in biological media, radiative transfer of polarized light, numerical aspects of radiative transfer.

This book presents a survey of modern theoretical and experimental techniques in studies of light scattering phenomena and radiative transfer processes in random media. It presents reviews on light scattering by sea water and bubbles, and includes a separate chapter addressing studies of the remote sensing of crystalline clouds with a focus on the shape of particles—a parameter rarely studied by passive remote sensing techniques. In particular, it offers a comprehensive analysis of polarized radiative transfer in optically active (e.g., chiral) light scattering media and explores advances in spectro-polarimetry of particulate media. Lastly it discusses new developments in light scattering for combustion monitoring.

Particle characterization is an important component in product research and development, manufacture, and quality control of particulate materials and an important tool in the frontier of sciences, such as in biotechnology and nanotechnology. This book systematically describes one major branch of modern particle characterization technology - the light scattering methods. This is the first monograph in particle science and technology covering the principles, instrumentation, data interpretation, applications, and latest experimental development in laser diffraction, optical particle counting, photon correlation spectroscopy, and electrophoretic light scattering. In addition, a summary of all major particle sizing and other characterization methods, basic statistics and sample preparation techniques used in particle characterization, as well as almost 500 latest references are provided. The book is a must for industrial users of light scattering techniques characterizing a variety of particulate systems and for undergraduate or graduate students who want to learn how to use light scattering to study particular materials, in chemical engineering, material sciences, physical chemistry and other related fields.