This book was originally published in 1976 as the third edition of a book first published in 1938. After 1950, when the previous edition was published, advancing technology made possible a great deal of experimental work on the properties of negative ions in gases. Photodetachment techniques became an important source of information about negative ions and provided values of electron affinities with accuracies which were previously unavailable. As knowledge of negative ions increased, the nature of their influence on the physical phenomena in which they are concerned was more readily understood. Inclusion of so much fresh material means that less emphasis is placed on some earlier knowledge and techniques. While it was necessary to restrict the introductory discussion of different branches of physics concerned, sufficient background is included to make comprehensible the subsequent specific discussion of applications to negative ions.
