With the death of Otto Hahn on 28 July the world has lost one of the most significant and successful scientists of our century. His most famous discovery, the fission of the uranium nucleus, has basically changed the political and economic world picture. Perhaps this discovery and its results have been more debated than any previous scientific step forward. There has hardly ever been a scientist who has been so generally respected and loved. It would be unjust, however, when considering Otto Hahn's scientific achievements, to think only of this one great discovery, made at the age of nearly 60, although it was the conclusion and crowning of his scientific career.

On 22 May a group of the nation's most distinguished scientists—including four Nobel laureates—gathered at Columbia University to take part in a one-day symposium marking the retirement of Isidor I. Rabi. Rabi, himself a Nobel laureate, completed a career that spans nearly 40 years with Columbia.

Paul A. Flinn, a Carnegie-Mellon University professor, has received one of the two Argonne Universities Association Distinguished Appointment Awards for 1971. The award will enable Flinn, who is professor of physics and metallurgy and materials science, principal research metallurgical engineer and senior fellow at Mellon Institute of Science, to devote next year exclusively to the study of glasses and amorphous materials at Argonne National Laboratory. He will also receive a $5000 merit award.

The isomer shift in Mossbauer spectroscopy refers to changes in the resonance energy resulting from electric-monopole hyperfine interaction between the finite nuclear-charge distribution and the electron density at the nucleus. For a typical source-absorber experiment, the shifts depend on two factors: the difference in mean radii for the resonant nuclear levels and the difference in electron densities at source and absorber nuclei. Thus, any treatment of isomer shifts implicitly involves nuclear-structure considerations together with determinations of electron-charge distributions in condensed matter. For a given Mossbauer isotope, the nuclear factor is essentially constant and a determination of this quantity (by calculation or electrondensity calibration) allows observed isomer shifts to be interpreted, in principle, as relative electron densities at source and absorber. The isomer or chemical shift was first reported in 1960 by O. C. Kistner and A. W. Sunyar for the case of an «FeiOa absorber and source of Co 57 in stainless steel. This important feature of Mossbauer spectroscopy has motivated a significant amount of research during the ensuing years, and this work is authoritatively surveyed in the present volume.

Synchrotron radiation, with its remarkable properties and eminent suitability for scientific and technical applications, is having a profound effect on the many disciplines that make use of radiation in the x-ray and vacuum ultraviolet regions of the spectrum. Indeed, the rapidly increasing availability of this radiation is revolutionizing some fields and is leading to a variety of new interdisciplinary collaborations. Seeking to take advantage of this incisive tool, scientists around the world are requesting time at synchrotron radiation facilities in such large numbers that the fast-paced construction of new sources—including several in less-developed countries—has yet to bring the level of availability up to that of demand.

In May 1981, PHYSICS TODAY devoted a special issue to synchrotron radiation research. Four articles reviewed facilities, applications and the then newly developed wiggler and undulator sources. In the intervening two years there have been very significant changes in the nature and availability of synchrotron radiation sources. Five new facilities have begun operation, and a similar number of facilities already in operation have undergone major expansions. The nature of synchrotron radiation research has also changed significantly, as have our expectations. Consequently, PHYSICS TODAY will publish a series of articles describing these changes in detail.

At a number of construction sites around the world, crews are laboring in and around large circular tracks to install the accelerators and storage rings that will form the basis of new synchrotron radiation facilities. Most of the budding facilities are designed to produce synchrotron radiation, in the soft- or hard-x-ray regions, that is far brighter than available sources can provide. They are sometimes described as the "third generation." According to this rough categorization, the first generation consists of circular accelerators originally intended for other purposes: They provide synchrotron radiation to parasitic experiments or, in some cases, they have become partially dedicated to such uses. The second generation comprises facilities specifically designed to support synchrotron radiation experiments, with the radiation produced primarily as electrons or positrons curved in the field of the machines' bending magnets. The third-generation machines, by contrast, are designed to optimize the radiation that is produced as the electrons or positrons traverse devices known as wigglers and undulators. The new machines will complement existing facilities, and they will provide more opportunities for the growing user community.

Willlibald Jentschke, founder and the first director of the German Electron Synchrotron (DESY) laboratory and a former director general of CERN, died peacefully on 11 March 2002 in Göttingen, Germany.

TODAY NEW DISCOVERIES in physics are rapidly assimilated. Although only nine years have passed since Rudolf Mossbauer submitted his first article, the Mossbauer effect is currently being used in many undergraduate physics laboratories, and four or five manufacturers are offering off-the-shelf Mossbauer spectrometers.

During the final weeks of World War II in Europe, as Allied armies swept across a chaotic, battle-torn Germany, two teams of the world's leading nuclear scientists were desperately at work. One team, sequestered in the New Mexican desert, hastened to assemble the atomic bombs that would shake the world later that summer. The other team, a group of Nazi-sponsored physicists and technicians in southern Germany, struggled to do something that, unbeknownst to them, the Allies had done two years earlier: build a critical, self-sustaining nuclear reactor.

Meanwhile, a different kind of team was running its own race against time. Convinced (erroneously) that the Germans were close to creating their own superweapon, the Allies sent an American unit of scientists, soldiers, and secret agents established by Lieutenant General Leslie R. Groves into Nazi Germany. Their orders: find the German scientific team before they could provide Hitler with atomic power. The scientific head of the mission: a Dutch-American physicist named Samuel A. Goudsmit. The mission code name: Alsos.

As his small entourage moved closer to the German research camp, Goudsmit revisited familiar people and places now changed forever by the war. The first Allied scientist to interrogate the captured physicists, Goudsmit heard first hand about life in a Nazi Germany in which they had lived and worked for over a decade. Most importantly, as the last person to review German nuclear research papers before military classification barred them from the public eye, Goudsmit was uniquely qualified to answer the most puzzling question: why, after their spectacular early successes, did German nuclear research efforts fall so miserably? Goudsmit's insights into the errors and hindrances that frustrated the German scientists, as well as his penetrating character analyses, remain uncannily accurate, as proven a half-century later by the now de-classified documents.

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