Atomic physics, discoveries

However, an important development within atomic physics, namely the discovery of isotopy in the 1910s, led some philosophically minded chemists to reexamine Mendeleev s distinction and to rehabilitate it in a modified form. With the rapid discovery of isotopes it began to seem as though there were far more "elements" than the 90 or so which were displayed on periodic tables at the time. The work of Soddy [14], in particular, served to clarify the situation, and one that had been anticipated by Crookes,... 

Hermetic and Rosicmdan circles such as the Golden Dawn began to engage more publicly with science after the discoveries of radiation, radioactive transformation, and radium. In a case like that of the Alchemical Society, two subjects, alchemy and radiation,4 allowed the groups from sharply different social worlds—those of mainstream science and occultism—to interact. These interactions also contributed to the popular press s alchemical understanding of the newly emerging discourse of atomic physics. 

Alex Keller s The Infancy of Atomic Physics Hercules in His Cradle (1983) is one of the finest such studies. Emilio Segre s From X-Rays to Quarks Modern Physicists and Their Discoveries (1980) is another excellent history, one that also focuses on the personalities of the physicists. 

Mass spectrometry is more than 100 years old and has yielded basic results and profound insights for the development of atomic physics. The rapid development of nuclear physics, in particular, would be unthinkable without the application of mass spectrometric methods. Mass spectrometry has contributed to conclusive evidence for the hypothesis of the atomic structure of matter. So far mass spectrometry has supplied specific results on the structure of the nucleus of atoms. Nobel prizes have been awarded to a number of scientists (Thomson, Wien, Aston, Paul, Fenn and Tanaka) associated with the birth and development of mass spectrometry, or in which mass spectrometry has aided an important discovery (e.g., for the discovery of fullerenes by Curl, Kroto and Smalley). 

But the relative strengths ofatomic lines differ from star to star. The confluence of atomic physics, of quantum mechanics, and of statistical mechanics has allowed astronomers to understand these variations in detail. These issues were at the heart of the revolution that was 20th-century physics but today they are understood. The net resultis that other stars have different abundances of the elements than does our own. Perhaps one should say modestly different. The broad comparisons between the elements remain valid - iron is quite abundant, vanadium is rather rare. That remains true but many stars have many fewer of each. A few have more of each. This was a great discovery of 20th-century astronomy, because it established the nucleosynthesis of the elements as an observational science. Astronomers also learned how old the stars are, for there do exist telltale signs of a star s age. The oldest stars are found to have many fewer of all chemical elements (except the three lightest elements) than does the Sun. These came to be called metal-poor stars, because the heavy elements were lumped together under the term metals by astronomers. It may seem paradoxical that the oldest stars have the fewest metals but the key is that the abundances within... 

The most recent advance in the theory of the helium atom was the discovery of its classically chaotic nature. In connection with modern semiclassical techniques, such as Gutzwiller s periodic orbit theory and cycle expansion techniques, it was possible to obtain substantial new insight into the structure of doubly excited states of two-electron atoms and ions. This new direction in the application of chaos in atomic physics was initiated by Ezra et al. (1991), Kim and Ezra (1991), Richter (1991), and Bliimel and Reinhardt (1992). The discussion of the manifestations of chaos in the helium atom is the focus of this chapter. 

Inorganic chemistry is descriptive in the sense that many branches of chemistry remain essentially descriptive. But the emphasis falls increasingly upon a description of its phenomena in terms of the discoveries of atomic physics, quantum mechanics, and theoretical and physical chemistry. Accordingly the earlier chapters seek to provide a minimum background for the rational understanding of chemical observations. The information is not intended to take the place of specific reading and instruction in physical and theoretical chemistry, but simply to give a handy, coherent synopsis of ideas which should enrich the appreciation of the chapters which follow. 

Finally, a subject of fundamental importance in atomic physics is the study of how electronic properties are modified by the atomic environment, as in molecules or in the solid state. New situations have been found at the frontier between atomic physics, molecular physics and the physics of condensed matter. This area has grown considerably with the discovery of giant resonances which, though atomic in origin, were first observed in the soft X-ray spectra of solids. Since then, resonant photoemission has become a well-established experimental technique in solid state physics, and valence fluctuations and intermediate valence effects in solids have been shown to involve localised orbitals which are partly atomic in character. 

It was a time of great excitement and ferment in science, and Rutherford s laboratory was one of the epicenters of discovery in atomic physics. The first coherent theory of the structure of the atom was just then being developed by Rutherford and his research group, which, besides Moseley, included Niels Bohr, Hans Geiger, Kasimir Eajans, and others. 

Optical spectroscopy of the simple hydrogen atom has played a central role in the development of atomic physics and quantum mechanics.3 The visible Balmer spectrum was the Rosetta stone which inspired the pathbreaking discoveries of Bohr, Sommerfeld, De Broglie, Schrbdinger, Dirac, and Lamb. More than once, seemingly minute discrepancies between theory and experiment led to important breakthroughs in our understanding of quantum physics. 

This is a fitting conclusion to this chapter, which has demonstrated how chemistry was by no means eclipsed by the discoveries in atomic physics, as is sometimes implied. The cases of Main Smith and Bury, in particular, show that chemists not only were able to compete with the atomic physicists on their own terms but also arrived at more detailed configurations before the physicists could do so. 

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