Einstein

Einstein — marelibri

Zur Quantentheorie des Strahlungsgleichgewichts. Offprint

1923rif. 432881923. 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 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. . unknown books

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Einstein, Albert and Paul EhrenfextABAA

Quantentheoretische Bemerkungen zum Experiment von Stern und Gerlach

1922rif. 432871922. Einstein Albert 1879-1955 and Paul Ehrenfest 1880-1933. Quantentheoretische Bemerkungen zum Experiment von Stern und Gerlach. Offprint from Zeitschrift für Physik 11 1922. 31-34pp. 229 x 155 mm. Original printed self-wrappers. Light toning but fine otherwise. First Edition Offprint Issue. In 1922 the physicists Otto Stern and Walther Gerlach conducted a now-classic experiment in which a beam of silver atoms was streamed through an inharmonious magnetic field in order to observe the atoms' deflection patterns. Rather than a random and continuous distribution as predicted by classical theory the atoms passing through the field were deflected up or down by a specific amount demonstrating that they had intrinsically quantum properties. The Stern-Gerlach experiment corroborated the Bohr-Sommerfeld model of the atom and strongly influenced later developments in 20th century physics. However the experiment also created some serious difficulties for quantum physicists in the period before the rise of the "new" quantum mechanics. Einstein and Ehrenfest addressed one of these difficulties-connected with space quantization-in their joint paper in which "they dealt in particular with the problem of how the orbits of the atom would obtain their discrete directions which they exhibit while passing through the inhomogeneous magnetic field. Under the assumption that the mechanism causing the orientation was provided by the interaction with the radiation field Einstein and Ehrenfest estimated that for a field strength of 10000 G a change in the direction of the orbit would take place in roughly 1011 s; this long time interval would be reduced in the presence of heat radiation at room temperature . . . to about 109 s. How could they asked the experimental situation be explained which implied that the discrete orientations of the orbits in silver atoms were obtained in less than 10-4 s. In order to deal with this evident puzzle Einstein and Ehrenfest proposed two alternatives: first that the silver atoms were always in the states of spatial quantization; second the orientations of the electron orbits arose from an interaction of the atoms with the radiation field which involved much smaller reaction times . . . However they found that both alternatives created considerable difficulties in the understanding of the atomic processes . . . Thus Einstein and Ehrenfest concluded: 'The difficulties mentioned above show how unsatisfactory are both interpretations of the results found by Stern and Gerlach'" Mehra & Rechenberg The Historical Development of Quantum Theory 1 pp. 443-444. Pais Subtle is the Lord p. 328. Weil Albert Einstein Bibliography 121. . unknown books

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