TAILIEUCHUNG - Early Atomic Models – From Mechanical to Quantum (1904-1913)

This book intends to fill the gap in the literature of mobile robots by containing, in a single reference, complete graphically presented infor- mation on the mechanics of a mobile robot. It is written in laymen’s lan- guage and filled with sketches so novices and those not trained in mechanical engineering can acquire some understanding of this interest- ing field. It also includes clever schemes and mechanisms that mid-level mechanical engineers should find new and useful. Since mobile robots are being called on to perform more and more complex and practical tasks, and many are now carrying one or even two manipulators, this book has a section on manipulators. | Early Atomic Models - From Mechanical to Quantum 1904-1913 Charles Baily Department of Physics University of Colorado Boulder Co 80309-0390 USA Abstract A complete history of early atomic models would fill volumes but a reasonably coherent tale of the path from mechanical atoms to the quantum can be told by focusing on the relevant work of three great contributors to atomic physics in the critically important years between 1904 and 1913 J. J. Thomson Ernest Rutherford and Niels Bohr. We first examine the origins of Thomson s mechanical atomic models from his ethereal vortex atoms in the early 1880 s to the myriad corpuscular atoms he proposed following the discovery of the electron in 1897. Beyond qualitative predictions for the periodicity of the elements the application of Thomson s atoms to problems in scattering and absorption led to quantitative predictions that were confirmed by experiments with high-velocity electrons traversing thin sheets of metal. Still the much more massive and energetic a-particles being studied by Rutherford were better suited for exploring the interior of the atom and careful measurements on the angular dependence of their scattering eventually allowed him to infer the existence of an atomic nucleus. Niels Bohr was particularly troubled by the radiative instability inherent to any mechanical atom and succeeded in 1913 where others had failed in the prediction of emission spectra by making two bold hypotheses that were in contradiction to the laws of classical physics but necessary in order to account for experimental facts. Contents 1 Introduction 2 The mechanical atoms of J. J. Thomson Rings of Saturn and ethereal vortices A corpuscular theory of matter The number of corpuscles in the atom 3 The nuclear atom of Ernest Rutherford . Fundamental properties of a-particles . The angular dependence of a-scattering . Competing theories and experimental data 4 The quantum atom of Niels Bohr Absorption and atomic .

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