Zur Quantentheorie des Strahlungsgleichgewichts. Offprint

1923. Einstein, Albert (1879-1955) and Paul Ehrenfest (1880-1933). Zur Quantentheorie des Strahlungsgleichgewichts. Offprint from Zeitschrift für Physik 19 (1923). 301-306pp. Original printed self-wrappers. 230 x 157 mm. Light toning but very good. First Edition, Offprint Issue. In 1916, after publishing his great work on general relativity, Einstein returned to the question of blackbody radiation. In November 1916 he wrote to his friend Besso that “a splendid light has dawned on me about the absorption and emission of radiation” (quoted in Pais, p. 405), one that led him to a new derivation of Planck’s radiation law and convinced him of the reality of (truncated) light-quanta (photons). After publishing these results in three papers, culminating with the famous “Zur Quantentheorie der Strahlung” (1917), Einstein kept looking for “new ways in which the existence of photons might lead to observable derivations from the classical picture” (Pais, p. 413). He found none until 1923, when Arthur Compton and Peter Debye independently derived the relativistic kinematics for the scattering of a photon off an electron at rest. The work of Compton and Debye led Wolfgang Pauli to extend Einstein’s work of 1917 to the case of radiation in equilibrium with free electrons (see Pais, p. 414n). “Pauli examined the requirements of detailed balance under Lorentz transformations and found that scattering of light by free electrons must include a term of a form which we would now call stimulated emission . . . Einstein and Ehrenfest then showed that Pauli’s results could be obtained by an extension of [Einstein’s] 1917 paper with the unnecessary specialization to discrete energy levels removed . . . The core of Einstein’s argument is that the scattering process should be broken into two parts: the absorption of energy from radiation of frequency 1 and the emission of energy as radiation of frequency 2” (Lewis, p. 42). Lewis, “Einstein’s derivation of Planck’s radiation law,” American Journal of Physics 41 (1973): 38-44. Pais, Subtle is the Lord, ch. 21. Weil, Albert Einstein Bibliography, 138. . (Inventory #: 43288)