Scattering from model nonspherical particles. Theory and applications to environmental physics. second edition.

Since the publication of the first edition of this book, we have become deeply involved in astrophysics research, particularly the study of the interstellar medium. Modeling scattering particles as layered spheres or as aggregates of spherical scatterers, expanding the electromagnetic field in a series of vector multipole fields, and resorting to the T-matrix approach for averaging over the orientations of a dispersion of nonspherical particles are effective tools for studying scattering theory, which we described and extensively applied in the first edition of this book. In fact, these tools also proved to be adequate for studying cosmic dust, even when they must be applied to a new range of current problems. We refer, for example, to the description of mechanical interaction of electromagnetic radiation with cosmic dust grains, which is believed to be of paramount importance in determining the dynamics of the grains. Since this book is conceived as a summary of our work, the desire to encompass all new topics led us to revise both its content and its structure. Of course, beyond the changes that we outline below, all chapters were carefully revised. Marginal changes and additions were made in Chap. 1, while Chap. 2 has been substantially revised to cover the light of general polarization and, in particular, with the description of the state of polarization of electromagnetic waves of general form. In this chapter we reserved ample space for the representation of the kinematics of the scattering processes both in the plane of scattering and in the meridional planes. We also discuss a generalization of the Stokes parameters that is suitable to describe the state of polarization of waves of general form. Chapter 3 presents novel material, dealing with the conservation theorems for combined systems of fields and particles, and with their consequences. Thus, this chapter deals not only with the widely known Poynting theorem, but also with the conservation of linear momentum, which is responsible for the radiation pressure and with the conservation of angular momentum, which may be responsible for the (at least partial) alignment of the cosmic dust grains, and the consequent linear polarization of starlight. The explicit expressions for the radiation force F_rad, the radiation torque Γrad and the emission force F_e are presented. Chapter 4 has been significantly revised. We introduce the appropriate multipole expansion for waves of general wavevector (both real and complex) and of general state of polarization. Formulas for the orientational averages have also been reported for particles with cylindrical symmetry. Radiation forces and torque dealt with in Chap. 3 are expressed here in terms of the transition matrix. Chapter 5, which deals with the calculation of the transition matrix of aggregates of spherical scatterers, now includes the case of metal spheres that can sustain the propagation of longitudinal waves. Chapter 6, dealing with scattering from particles in the vicinity of a plane interface, is almost unchanged. Nevertheless, we added new material relating to total internal reflection and scattering of evanescent waves, which is presently considered a good method to study the properties of biological particles, and is also relevant for near-field spectroscopy. Chapter 7 has been greatly enlarged to include a number of new applications, such as the scattering by aggregates of large spheres, and by aggregates of metal spheres sustaining longitudinal waves. We also include applications regarding the radiation force and torque on aggregates of spherical scatterers as well as regarding the force due to the emission of radiation. The only addition to Chap. 8 relates to the scattering of evanescent waves both from single spheres and from aggregated spheres. No changes have been made in Chap. 9, while Chap. 10 now contains a few new sections on the effect of radiation pressure and radiation torque on cosmic dust grains. We also added a study of the morphology of the dust grains and of the distribution and polarization of the electromagnetic field in the interior of aggregated dust grains. The subject of these new sections was inspired by the wide interest of the astrophysicist community in the dynamics of the interstellar medium and in astrochemistry. We renew our thanks to Dr. Orazio I. Sindoni, Dr. Maria Antonia Iatì, Prof. Santi Aiello and Dr. Cesare Cecchi-Pestellini, who we also mentioned in the first edition and who were partners in the research we report in this book. We also gratefully acknowledge the efforts of Dr. Arianna Giusto. We want to express our sincere thanks to Prof. David Williams, University College London, whose understanding of all aspects of the astrophysical research has been the inspiration behind our astrophysics working, and Prof. Flavio Scappini, Istituto per i Materiali Nanostrutturati del Consiglio Nazionale delle Ricerche, Bologna, whose knowledge of astrochemistry was invaluable when facing certain aspects of the chemical effects of the radiation. We are grateful to several colleagues for fruitful discussions that helped us in revising the book. In particular, our sincere thanks go to Prof. Nikolai Voshchinnikov, Sobolev Astronomical Institute, St. Petersburg, Russia, who gave us good advice on the didactical aspects of the book. Last, but not least, we want to thank Springer, to whose publishing policy we owe the printing of this enlarged edition.