Free Electrons in Metals 1865-1943 Pieter Zeeman [Wikipedia] 1853-1928 Hendrik Antoon Lorentz [Wikipedia] 1863-1906 Paul Drude [Wikipedia] 1881-1948 Richard Chace Tolman [Wikipedia] 1890-1958 Thomas Dale Stewart [Wikipedia]
1896 1897	Pieter Zeeman discovered splitting of emission wavelength of solium (Na) in magnetic field. P. Zeeman On the influence of magnetism on the nature of the light emitted by a substance London, Edinburgh, and Dublin Philosophical Magazine Journal of Science 5th Series, Volume 43, pp. 226-237 (1897). [DOI] P. Zeeman Over den invloed eener magnetisatie op den aard van het door een stof uitgezonden licht (op Zaterdag 31 October 1896) Koninklijke Akademie van Wetenschappen te Amsterdam Verslagen van de gewone vergaderingen der Wis- En Natuurkundige Afdeeling, Deel V. van 30 Mei 1896 tot 21 April 1897 (Johannes Müller, Amsterdam, 1897) pp. 181-184. [Archive] P. Zeeman Over den invloed eener magnetisatie op den aard van het door een stof uitgezonden licht, II (van Zaterdag 28 November 1896) Koninklijke Akademie van Wetenschappen te Amsterdam Verslagen van de gewone vergaderingen der Wis- En Natuurkundige Afdeeling, Deel V. van 30 Mei 1896 tot 21 April 1897 (Johannes Müller, Amsterdam, 1897) pp. 242-248. [Archive] English Translation Kamerlingh Onnes Communications from the Physical Laboratory at the University of Leiden No. 25-36 April 1893-January 1897 Eduard Ijdo, Leiden, 1897 [LeidenUnivArchive]->[Communications]->[25-36] P. Zeeman The effect of magnetisation on the nature of light emitted by a substance Nature, Volume 55, pp. 347-347 (1897). [DOI] Lorentz's Predictions and Zeeman's Observation - Circular polarization of the light of which wavelength is splitted by magnetic field. - The value of e/m, which can be calculated in Lorentz's theory, matched to the value measured by J. J. Thomson.
1895 1906	Hendrik Antoon Lorentz Light emission from an object is due to harmonic oscillation of charged particles in the atom. His theory explained the splitting of the emission wavelength by the magnetic field. H. A. Lorentz Versuch einer Theorie der electrischen und optischen Erscheinungen in bewegten Körpern (Brill, Leiden, 1895). [Wikisource] [MPG] H. A. Lorentz Versuch einer Theorie der electrischen und optischen Erscheinungen in bewegtenKörpern (B. G. Teubner, Leipzig, 1906). [Archive(1906)]
1897	Pieter Zeeman m/e could be obtained from the relationship between the magnetic field and the wavelength splitting. The values were in good agreement with the m/e of "corpuscle" measured by J. J. Thomson. P. Zeeman Doublets and triplets in the spectrum produced by external magnetic forces London, Edinburgh, and Dublin Philosophical Magazine Journal of Science 5th Series, Volume 44, pp. 55-60 (1897). [DOI]
1899	J. J. Thomson and The Photoelectric Effect When a surface were exposed to electromagnetic radiation with the energy above a certain threshold, charged particles were emitted from the surface. J. J. Thomson revealed that e/m of emitted charged particles was the same with his "corpuscles"(=electrons) observed in the cathode rays. J. J. Thomson On the existence of masses smaller than atoms (Saturday, September 16), in Report of the Sixty-Ninth Meeting of the British Association for the Advancement of Science held at Dover in September 1899 (John Murray, London, 1900) pp. 637-637. [BioDiversityLib] J. J. Thomson On the masses of the ions in gases at low pressures London, Edinburgh, and Dublin Philosphical Magazine Journal of Science 5th Series, Volume 48, pp. 547-567 (1899). [DOI]
1900	Paul Drude Classical theory of electric conduction by motion of charged particles. Particles of mass m and charge e move around in the solid as in the gas. P. Drude Zur Elektronentheorie der Metalle. I. Teil Annalen der Physik, Volume 306, pp. 566-613 (1900). (Vierte Folge Volume 1) [DOI] [Google] [Archive] P. Drude Zur Elektronentheorie der Metalle. II. Teil Galvanomagnetische und thermomagnetische Effecte Annalen der Physik, Volume 308, pp. 369-402 (1900). (Vierte Folge Volume 3) [DOI] [Archive] [Archive] [Google] [Google] [Google]
1916	Richard Chase Tolman and Thomas Dale Stewart Experimental and conclusive evidence that the transport of free electrons in solids is an electric current. They suddenly stopped the rotating metal coil at high speed and measured the voltage generated at that time. R. C. Tolman and T. D. Stewart The electromotive force produced by the acceleratio of metals Proceedings of the National Academy of Sciences of the United States of America, Volume 2, pp. 189-192 (1916). [DOI] R. C. Tolman and T. D. Stewart The electromotive force produced by the acceleration of metals Physical Review, Volume 8, pp. 97-116 (1916). [DOI]
	Toward Quantum Mechanics There were still many un-explained behaviors of electrons in solids. It has gradually become clear that classical mechanics and electromagnetism can no longer solve this problem.