This Advanced Study Institute was held at \-lellesley College, Wellesley, MA. , from 3 to 12 August 1980. It followed by four years the second "Capri ~,chool on Photon Correlation Spectroscopy". During the intervening period there had been many new applications of dynamic light scattering techniques to the study of systems whose properties depend either on collective molecular interactions or on the formation or activity of supramo1ecu1ar structures. Con sequently, emphasis at this conference was on light scattering studies of subjects such as dynamical correlations in dense polymer solutions, phase transitions in gels, spinodal decomposition of binary fluids, Benard instabilities in nonequilibrium fluids, the formation of micelles and phospholipid vesicles, and movements of the molecular assemblies of muscle tissue. The instructional pro gramme also included tutorial lectures on two complementary spec troscopic techniques which have benefited from dramatic advances in instrumentation, these being small angle X-ray (SAXS) and small angle neutron (SANS) scattering. Strong cold neutron and synchro tron X-ray sources have become available, and data now can be acquired rapidly with newly developed position-sensitive detectors. Several reviews of recent applications of SAXS and SANS were also provided. The organizers of the ASI hoped to provide a forum for theoreticians and experimentalists to assess advances in fields which, although related, were sufficiently different that a great deal of unfamiliar information could be communicated. The order ing of the papers in this volume closely approximates that of the talks presented at the Advanced Study Institute.

Laser Light Scattering: Basic Principles and Practice, Second Edition deals with the technical aspects of laser light scattering, including the basic principles and practice. Topics covered include light scattering theory, optical mixing spectrometry, photon correlation spectroscopy, and interferometry. Experimental methods and methods of data analysis are also described. This book is comprised of eight chapters and begins with a discussion on the interrelationship between laser light scattering and other types of scattering techniques that use X-rays and neutrons, with particular reference to momentum and energy transfers as well as time-averaged and time-dependent scattered intensity. The spectrum of scattered light and a single-particle approach to time-averaged scattered intensity are considered. The following chapters focus on photoelectric detection of the scattered electric field; optical mixing spectrometers; basic equations for photon correlation spectroscopy; and the principles of Fabry-Perot interferometry. The pertinent features of the experimental aspects of laser light scattering are also outlined, together with the Laplace inversion problem. The final chapter examines polymer molecular-weight distributions in relation to particle sizing. This monograph will be of interest to physicists.

Several previous Advanced Study Institutes have concentrated on the techniques of light scattering, while the biological appli cations were not fully explored. Many of the techniques are now standardised and are being applied to a wide range of biologically significant problems both in vivo and in vitro. While laser light scattering methods are superior to conventional methods, there was a general reluctance among biologists to adopt them because of the complexity of the physical techniques and the accompanying mathe matical analysis. Consequently valuable opportunities for advancing the understanding of the biological problems were being missed. Advances in the design and commercial availability of standard light scattering instruments, and the availability of standard computer programs, made the more widespread use of these techniques a practical reality for the biologist. While biologists are unable to cope with the complexities of the physical techniques, physicists are generally unaware of the nature and scale of the biological problems. The meeting at Maratea was an attempt to bring these two groups together and provide an impetus for the application of laser light scattering techniques to biology. This volume differs from the three previous proceedings on laser light scattering in the NATO ASI series (B3, B23, B73), in that it has been published in the Life Sciences series rather than the Physics series, reflecting the shift in emphasis from the development of a new technique to its application in biology.

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.

In the twenty years since their inception, modern dynamic light-scattering techniques have become increasingly sophisticated, and their applications have grown exceedingly diverse. Applications of the techniques to problems in physics, chemistry, biology, medicine, and fluid mechanics have prolifer ated. It is probably no longer possible for one or two authors to write a monograph to cover in depth the advances in scattering techniques and the main areas in which they have made a major impact. This volume, which we expect to be the first of aseries, presents reviews of selected specialized areas by renowned experts. It makes no attempt to be comprehensive; it emphasizes a body of related applications to polymeric, biological, and colloidal systems, and to critical phenomena. The well-known monographs on dynamic light scattering by Berne and Pecora and by Chu were published almost ten years ago. They provided comprehensive treatments of the general principles of dynamic light scat tering and gave introductions to a wide variety of applications, but natu rally they could not treat the new applications and advances in older ones that have arisen in the last decade. The new applications include studies of interacting particles in solution (Chapter 4); scaling approaches to the dynamics of polymers, including polymers in semidilute solution (Chapter 5); the use of both Fabry-Perot interferometry and photon correlation spectroscopy to study bulk polymers (Chapter 6); studies of micelIes and microemulsions (Chapter 8); studies of polymer gels (Chapter 9).

Advances in Botanical Research