Lasers In Chemical Processing

Laser Processing and Chemistry gives an overview of the fundamentals and applications of laser-matter interactions, in particular with regard to laser material processing. Special attention is given to laser-induced physical and chemical processes at gas-solid, liquid-solid, and solid-solid interfaces. Starting with the background physics, the book proceeds to examine applications of laser techniques in micro-machining, and the patterning, coating, and modification of material surfaces. This fourth edition has been revised and enlarged to cover new topics such as 3D microfabrication, advances in nanotechnology, ultrafast laser technology and laser chemical processing (LCP). Graduate students, physicists, chemists, engineers, and manufacturers alike will find this book an invaluable reference work on laser processing.

The possibility of initiating chemical reactions by high-intensity laser exci tation has captured the imagination of chemists and physicists as well as of industrial scientists and the scientifically informed public in general ever since the laser first became available. Initially, great hopes were held that laser-induced chemistry would revolutionize synthetic chemistry, making possible "bond-specific" or "mode-specific" reactions that were impos sible to achieve under thermal equilibrium conditions. Indeed, some of the early work in this area, typically employing high-power continuous-wave sources, was interpreted in just this way. With further investigation, however, a more conservative picture has emerged, with the laser taking its place as one of a number of available methods for initiation of high-energy chemical transformations. Unlike a number of these methods, such as flash photolysis, shock tubes, and electron-beam radiolysis, the laser is capable of a high degree of spatial and molecular localization of deposited energy, which in turn is reflected in such applications as isotope enrichment or localized surface treatments. The use of lasers to initiate chemical processes has led to the discovery of several distinctly new molecular phenomena, foremost among which is that of multiple-photon excitation and dissociation of polyatomic molecules. This research area has received the greatest attention thus far and forms the focus of the present volume.

It has often been said that the laser is a solution searching for a problem. The rapid development of laser technology over the past dozen years has led to the availability of reliable, industrially rated laser sources with a wide variety of output characteristics. This, in turn, has resulted in new laser applications as the laser becomes a familiar processing and analytical tool. The field of materials science, in particular, has become a fertile one for new laser applications. Laser annealing, alloying, cladding, and heat treating were all but unknown 10 years ago. Today, each is a separate, dynamic field of research activity with many of the early laboratory experiments resulting in the development of new industrial processing techniques using laser technology. Ten years ago, chemical processing was in its infancy awaiting, primarily, the development of reliable tunable laser sources. Now, with tunability over the entire spectrum from the vacuum ultraviolet to the far infrared, photo chemistry is undergoing revolutionary changes with several proven and many promising commercial laser processing operations as the result. The ability of laser sources to project a probing beam of light into remote or hostile environments has led to the development of a wide variety of new analytical techniques in environmental and laboratory analysis. Many of these are reviewed in this book.

Chemical and Biological Applications of Lasers, Volume V focuses on the laser applications in photochemistry and spectroscopy. This book examines the spectroscopic detection of single atoms and explores the purification of industrial chemicals. Organized into seven chapters, this volume starts with an overview of the methods developed for laser detection of single atoms, including fluorescence, photoionization, photodeflection, and their combinations. This text then discusses the methods of high resolution spectroscopy, which provide detailed information on molecular structure and reaction kinetics studies. Other chapters review several laser photodissociation studies, which explain dissociation dynamics. This book discusses as well the possibilities for selective photochemical reactions and examines the potential of lasers for practical application in chemical processing. The final chapter considers the various metals that can undergo a photochemical change in oxidation state in ordinary solvents. This book is a valuable resource for physicists, chemists, electrochemists, photochemists, electrical engineers, and chemical engineers.

Materials processing with lasers is a rapidly expanding field which is increasingly captivating the attention of scientists, engineers and manufacturers alike. The aspect of most interest to scientists is provided by the basic interaction mechanisms between the intense light of a laser and materials exposed to a chemically reactive or nonreactive surrounding medium. Engineers and manufacturers see in the laser a new tool which will not only make manufacturing cheaper, faster, cleaner and more accurate but which also opens up entirely new technologies and manufacturing methods that are simply not available using existing techniques. Actual and potential applications range from laser machining to laser-induced materials transformation, coating, patterning, etc. , opening up the prospect of exciting new processing methods for micromechanics, metallurgy, integrated optics, semiconductor manufacture and chemical engineering. This book concentrates on the new and interdisciplinary field of 1 aser-i nduced chemicaZ process i ng of materi als. The techni que permits maskless single-step deposition of thin films of metals, semiconductors or insulators with lateral dimensions ranging from a few tenths of a micrometer up to several centimeters. Moreover, materials removal or synthesis, or surface modifications, such as oxidation, nitridation, reduction, metallization and doping, are also possible within similar dimensions. This book is meant as an introduction. It attempts to cater for the very broad range of specific interests which different groups of readers will have, and this thinking underlies the way in which the material has been arranged.