Atom, Molecule,and Cluster Beams

With the publication in two parts of volume 6 of The Historical Development of Quantum Theory, Jagdish Mehra and Helmut Rechenberg have completed their ambitious project. These six volumes represent an extraordinary amount of painstaking scholarship: In volume 6 alone are 1265 footnotes containing detailed information on persons in the text. The references to the 1252 pages of text of the two parts require 182 pages, and the author index runs to 27 two-column pages. A similar amount of scholarly apparatus is appended to each of the previously published volumes. The subject index to the six volumes, in part two of volume 6, takes 143 two-column pages! And this is not to mention the many interviews the authors conducted; the hunting down of unarchived correspondences; the background research on such subjects as the history of group theory, the history of probability, the history of causality, the political, economic, social, cultural, and intellectual histories of the countries involved, to name a few; plus the time and effort to master the technical matters they write about.

In Atom, Molecule and Cluster Beams, Hans Pauly has emphasized areas in the field that were just emerging when the last significant work on the subject was published--Atomic and Molecular Beams Methods, edited by Giacinto Scoles (Vols. I and II, Oxford U. Press, New York, 1988, 1992). The applications of cluster, fast translational, and slow atomic beams, the trapping and cooling of atoms, and the use of atomic optics were among Pauly's chosen topics.

Pauly is the retired director of atomic and molecular physics at the Max Planck Institute for Flow Research in Göttingen, Germany. He has the perspective and expertise to undertake such a book. While the books by Scoles and the recent monograph Atomic and Molecular Beams: State of the Art 2000, edited by Roger Compargue (Springer, 2001) contain contributions from a large number of authors, Pauly clearly states that his contribution "reflects the tastes and inclinations of the author." This enables him to present each topic with a degree of uniformity and consistency that is very hard to achieve in a compendium volume. Pauly's treatment of each chapter is thorough, from the adequate and accurate presentations in volume I of the basic theories and principles of gas kinetics and dynamics that form the foundation of the field, to the numerous applications and examples of methodology in volume II.

Beams provide a unique view of the fundamental properties of atoms and molecules, a view that cannot be duplicated under condensed-phase conditions. Major advances have occurred in the field since the Scoles volumes were published, particularly in the areas of metrology, atom optics, and the use of cluster beams to bridge the gap between isolated atoms and molecules and the condensed phase. The potential impact on a diverse range of areas (materials, environmental, chemical, and biological sciences) is enormous. There is more than ample justification for publishing a new source that would benefit both established researchers and those wishing to gain an introduction to and understanding of the field. Pauly is successful in many, but not all aspects of this undertaking.

The first volume has some overlap with Scoles's counterpart volume. However the benefits of single authorship are quite clear. The common topics are presented more completely and with focus, excellent accuracy, and superb references. The chapters on gas kinetics and dynamics as applied to molecular beams are among the best available. The extensive compilation of thermal beam sources contained a number that were new to me, which I noted for further consideration. While the strengths of this volume were apparent, it left me with a slight concern that only a small portion was related to spectroscopy, where molecular and atomic beams have had and continue to have a significant impact.

The second volume clearly reflects the author's tastes and inclinations. The presentations on fast beams, velocity measurement and selection, and state selection, while accurate, place more emphasis on methods and techniques that are not widely used today in the molecular beam community. This is perhaps most clearly shown in that only a brief discussion of optical methods in state selection is given. There are literally tens of approaches using incoherent or coherent methods, not only for state selection in atoms or molecules but for size- or composition-selected clusters as well. The treatment in Scoles's first volume placed considerable emphasis on spectroscopic techniques, although they are now somewhat dated. The remaining portions of Pauly's second volume on cluster beams, slow atom beams and traps, and atom optics are more modern and useful. While the latter topics are covered extensively by a number of contributors in the first section of the book edited by Compargue, I preferred the chapter by Pauly. The single-author approach again had a decided advantage.

At the risk of sounding ethnocentric, Pauly's effort reflects a traditional European view of atom and molecular beams. There is a decided emphasis on the physics behind the techniques and applications, with less emphasis on both spectroscopy and chemistry; the approach from the US seems to be the complement.

The two volumes by Pauly clearly belong on the shelf for individuals interested in beams. The reasons are that the first volume presents a unified description of the basic theory and principles, while the second contains a recollection of the past and present methods, with the promise of new techniques for the future.