Table of contents

The development of three directions in nuclear physics, originating from three ideas of Niels Bohr, is analyzed: 1) the compound nucleus: is the compound state entirely chemical? what does the energy distribution of neutron resonances imply? "dynamic intensification" of weak effects; the role of fluctuations and the description of the kinetics; and, pre-equilibrium processes; 2) collective motions: how the collective and single-particle degrees of freedom coexist with one another; parallel formation of the shell model and the theory of collective oscillations; the generalized model; the problem of the moment of inertia; pair correlations and "superfluidity" in the nucleus; giant resonances; and theory of finite Fermi systems; and, 3) the fission process: fission in the liquid drop model and in the generalized model; shell corrections; double-hump fission barriers; fission isomers; nonconservation of parity in fission; and, "exotic" asymmetric fission. The emphasis is on the elucidation of the development of physical ideas, so that computational details are omitted.

Niels Bohr's studies on the quantum theory of the atom over the years 1912–1923 are discussed. The sources of his work on these questions are analyzed. The beginning of his quantum studies in 1912 is described. His famous paper on the theory of the hydrogen atom and on the origin of spectra is analyzed in detail. The subsequent development of his ideas regarding atomic structure is discussed, with an emphasis on his postulates regarding stationary states and radiative transitions and on the development of the correspondence principle. How well he understood the difficulties of the model theory and how he strived for a profound understanding of quantum phenomena are shown.

The way of thinking and scientific style of Niels Bohr are discussed in connection with developments of his emotional and spiritual life. Analysis of the papers of Bohr, his predecessors, and his contemporaries reveals that he was a philosopher of physics who had an incomparable influence upon the creation and development of quantum mechanics. His struggle against nuclear weapons is mentioned.