## On the Quantum Theory of Line-Spectra, I-III.

Copenhagen: Bianco Lunos, 1918-1922.

A rare complete set of his major work in the scarce presentation-offprint issue; with ‘Separate Copy’ printed on the front wrappers. Inscribed by Bohr to Austrian physicist Egon von Schweidler (1873-1948) on the front wrapper of the first part.

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 referred 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 system. 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 finally built into the foundation of quantum mechanics. *Provenance*: Bohr presented this copy to Austrian physicist Egon von Schweidler, head of the department of experimental physics at the University of Innsbruck and the author of several works on relativity. Segrè, X-Rays to Quarks, pp. 13-15; 119-30. Nobel: The Man and his Prizes, pp. 437-49.

Three parts. 4to: (270 x 215 mm). Offprints from: ‘Mémoires de l’Académie Royale des Sciences et des Lettres de Danemark’. Original printed wrappers in fine condition. Part I inscribed by Bohr “Herrn Professor Dr. v. Schweidler Rechtachtungsvoll vom Verfasser” (inscription slightly affected by chip in upper right corner).

Item #3545

**
Price:
$25,000.00
**