FROM THE PREFACE: This book deals with the foundations of the quantum theory of scattering. Scattering theory may be regarded either as a branch of mathematical physics or, increasingly, as a branch of mathematics worthy of independent study in its own right. The importance of spectral analysis to the theory is central; every modern text on scattering theory makes reference to the methods and ideas of spectral analysis, and conversely any comprehensive treatment of spectral theory will refer to methods and ideas drawn from applications to quantum theory, and to quantum scattering in particular. Much of the material in this volume, while relating to important aspects of the theory, is new or is presented for the first time in book form.