## On the Quantum Theory of Line-Spectra, I-III [all published].

modernphysics. Copenhagen: Bianco Luno, 1918-1922.

A fine set of this major work: It was in this fundamental paper that Bohr first gave a clear formulation of, and fully utilized, his 'correspondence principle'. Besides his derivation of the Balmer formula (1913), this is by many considered to be Bohr's greatest contribution to physics. Bohr's correspondence principle (or postulate) states in general that although classical physics is incomplete there must be a fundamental analogy between quantum theory and classical physics. Actually Bohr at first reffered to the postulate as the 'principle of analogy'. It was Bohr's underlying idea that the new quantum theory must satisfy in the limiting cases, e.g., when frequencies *v* tend to zero or quantum numbers *n→∞*, that it's predictions approximate those of classical physics. When studying different quantum theoretic problems one can thus utilize already established facts from what classical physics predicts in that particular situation, and then work backwards to arrive at new quantum theoretic rules for the systsem. In this major paper, of which the two first parts were published in 1918 and the third in 1922, Bohr penetrated far into the quantum theory of line-spectra of the Hydrogen atom, and other elements, by using his principle and the classical theory of electrodynamics. Bohr's method was the principle guide to the progress of quantum theory during the early twenties, until it was finaly built into the foundation of quantum mechanics.

4to: 268 x 218 mm. Published as Fasc. 1-3, no. 1, vol. 4 of the 8th series of 'Mémoires de l'Académie Royale des Sciences et des Lettres de Danemark'. 118 pp. All three parts bound in one fine half morrocoo, signed Ole Olsen 1980 Co'libri. All front and back wrappers withbound, a fine set.

Item #2257

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