Hydrogen: The Essential Element ,

John S.
Harvard U. Press
Cambridge, Mass.
, 2002. $28.00 (280 pp.). ISBN 0-674-00738-7

John S. Rigden’s book, Hydrogen: The Essential Element, could be subtitled, “The Hydrogen Atom’s Impact on Physics in 23 Nutshells.” The book begins in chapter 1 with the creation of protons in the big bang and ends in chapter 23 with such hydrogen exotica as positronium and Rydberg atoms. In between are engaging discussions of topics that include the invention of nuclear magnetic resonance, the discovery of the Lamb shift and the anomalous magnetic moment of the electron, and the hydrogen atom’s role in the birth of quantum mechanics.

Rigden, special projects director of the American Institute of Physics, is personally familiar with many of the heroes of these nutshells and with the importance of their work. His mastery of the subject has helped give the narrative vividness and accuracy that are seldom matched in semipopular science books.

The book contains a wonderful collection of anecdotes, many new to me, about famous physicists whose lives were touched by the hydrogen atom. For example, pages 132–133 contain a bittersweet description of how graduate student Norman Ramsey worked himself out of a thesis topic by finding magnetic-resonance lineshape anomalies that led to the discovery of the deuteron’s quadrupole moment. “Since Rabi sensed that something significant lurked in the peculiar signal shapes, he invited other members of his research team to participate in this potentially important experiment. As a result, Ramsey had to find another dissertation topic.”

Complementing the text are good photographs both of people and of historically interesting data. For example, a telling series of three resonance curves, for beams of molecular hydrogen and deuterium, shows the progression from Ramsey’s first, rather noisy signals to later beautifully resolved resonances of I. I. Rabi’s group from which the electron’s quadrupole moment was determined. The quadrupole moment showed that the force between protons and neutrons was not purely central but had a substantial, spin-dependent tensor component.

Each chapter is self-contained and is just the right length for 5 or 10 minutes of light reading before bedtime. Equations are limited to such simple examples as Balmer’s formula for the wavelengths of the hydrogen spectra, and Dirac’s deceptively simple version of the Schrödinger equation.

A few more diagrams of basic experimental arrangements would have been helpful to the nonexpert reader. For example, the book has many discussions of spectral lines, but no diagram of the refraction of light into its constituent colors, something that even Isaac Newton considered essential for his celebrated Opticks.

Although Rigden gives credit to experimentalists, he reserves his most reverent passages for theorist heroes. His emphasis on theory causes some eccentricities in the historical perspective. For example, there are three references to “spin” in the index, two to the Dirac theory of the electron and one to the respective integer and half-integer spins of bosons and fermions. Samuel Goudsmit’s name does not appear in the index. Goudsmit’s noted colleague George Uhlenbeck is mentioned in a single sentence: “ ‘The Schrödinger theory came as a great relief,’ said George Uhlenbeck, the codiscoverer of the electron spin” (p. 81).

Although precise studies of the hydrogen atom have had enormous and indisputable importance in the development of physics, one might question the primacy that Rigden assigns to hydrogen. Studies of the alkali-metal atoms have had comparable importance in the development of atomic clocks and in the discovery of the Fraunhofer D lines, electron spins, and Bose–Einstein condensation. Silicon, which launched salient developments in condensed matter physics, underpins our information age. Rigden makes little mention of accelerators, which have been essential for our understanding of the subatomic world. True to its title, the book keeps hydrogen as the guiding theme.

I intend to keep Hydrogen: The Essential Element close at hand as I prepare lectures on quantum mechanics. The personalities of scientists who have revealed the rich physics of the hydrogen atom shine through clearly, and will help to capture the imagination of new generations of young scientists.