On the Quantum Theory of Line-Spectra, Part I - III. - [BOHR'S CORRESPONDENCE PRINCIPLE]

1922. København, Bianco Lunos Bogtrykkeri, 1918 - 1922. 4to. Uncut unopened in the original printed wrappers. In "D. Kgl. Danske Vidensk. Selsk. Skrifter, afd., 8, række IV, 1-3" / "Mémoires de l'Académie Royale des Sciences et des Lettres de Danemark". Wrapper with a few minor nicks and tears but otherwise a very fine and clean copy. 118 pp. Collected offprint-edition of Bohr's seminal work "On the Quantum Theory of the Line-Spectra", marking the beginning of the quantum revolution in physics, introduced the concept of quantized energy levels, provided an explanation for the observed line spectra, and served as a foundational model that inspired further developments in quantum mechanics. It is conseidered one of Bohr's most important papers and the basis for his Nobel Prize. These papers give the first clear formulation of his 'correspondence principle' establishing the limit agreement of quantum and classical physics. "By 1918 Bohr had visualized, at least in outline, the whole theory of atomic phenomena. ... He of course realized that he was still very far from a logically consistent framework wide enough to incorporate both the quantum postulates and those aspects of classical mechanics and electrodynamics that seemed to retain some validity. Nevertheless, he at once started writing up a synthetic exposition of his arguments and of all the evidence upon which they could have any bearing; in testing how well he could summarize what was known, he found occasion to check the soundness of his ideas and to improve their formulation. In the present case, however, he could hardly keep pace with the growth of the subject; the paper he had in mind at the beginning developed into a four-part treatise, 'On the Theory of Line Spectra', publication of which dragged over four years without being completed; the first three parts appeared between 1918 and 1922, and the fourth, unfortunately, was never published. Thus, the full impact of Bohr's view remained confined to the small but brilliant circle of his disciples, who indeed managed better than their master to make them more widely known by the prompter publication of their own results" (D.S.B. 2: 246-47).