PREFACE Having finally retired to the peace and tranquility of rural south-west France, it came as something of a shock to be firmly reminded by my publisher that the apparently statutory eight years had passed since the last edition of this text. Even worse, for several years my only connection with spectroscopy has been the fact that France now uses nuclear magnetic resonance spectroscopy routinely in the quality control of its wines-a tenuous, but nonetheless very pleasant, connection. With some misgivings, therefore, I accepted McGraw-Hill's sugges- tion that I find a co-author to do the necessary work for me. My fears were groundless-not only was the experience of again working with a young and lively mind a great pleasure, but I feel sure we have also produced a much-improved book. A bonus was that my co-author's spouse, being a physicist, was able to contribute a different viewpoint to our discussions (which almost never became arguments), and greatly helped us to clarify our writing in several areas. The most obvious change in this revision is the addition of a totally new chapter on the spectroscopy of surfaces and solids. These techniques require very sensitive instrumentation, and it is only in recent years that some of them have become routine; they are included here because the topic has most certainly come of age and will become increasingly important in the future. Many rely on the use of high-intensity sources, such as the synchrotron, or on the application of Fourier transform principles. The latter were introduced in the last edition, but, as their use has become much more widespread, they receive an enhanced coverage in this, some techniques sections having been completely revised to take account of the new methods.