Physics in Perspective

, Volume 16, Issue 3, pp 293–343 | Cite as

The Franck-Hertz Experiments, 1911–1914 Experimentalists in Search of a Theory

With an appendix, “On the History of our Experiments on the Energy Exchange between Slow Electrons and Atoms” by Gustav Hertz
  • Clayton A. GearhartEmail author


In 1911, James Franck and Gustav Hertz began a collaboration to investigate the nature of collisions of slow electrons with gas molecules that led to a series of carefully planned and executed experiments, culminating in their discovery of inelastic collisions of electrons with mercury vapor atoms in 1914. This paper tells the story of their collaboration and the eventual reinterpretation of their results as a confirmation of Niels Bohr’s new atomic theory, largely as a result of experiments done in North America during the Great War.


James Franck Gustav Hertz John Sealy Edward Townsend J. J. Thomson Niels Bohr Robert Pohl Wilhelm Westphal Lise Meitner Ernest Rutherford electron ion mobility ionization affinity resonance 



It is a pleasure to acknowledge the following individuals and institutions: Roger Stuewer, Anne Lee Bain, Peter Pesic, and an anonymous referee read earlier versions of this paper and made numerous helpful comments and suggestions, as did Oliver Hertz for both the paper and my translation of Hertz’s essay. Allan Franklin and Michel Janssen likewise made helpful comments and suggestions in the course of several conversations. Dieter Hoffmann kindly called Gustav Hertz’s 1968 Lindau lecture to my attention. I am grateful to Hans Hertz, Oliver Hertz, and the Special Collections Research Center, University of Chicago Library, for permission to publish my translation of Gustav Hertz’s essay, and to the Niels Bohr Library, American Institute of Physics, for permission to quote from the James Franck interview file. The staff of the Special Collections Research Center kindly obtained photocopies for me of material in their James Franck Collection. Janine Lortz and the interlibrary loan staff of the Clemens and Alcuin Libraries of the College of St. Benedict/St. John’s University were, as always, indefatigable in tracking down often obscure sources. Needless to say, any errors of fact or interpretation that remain are entirely my own.


  1. 1.
    For more on Townsend, see Thaddeus J. Trenn, “John Sealy Edward Townsend,” in Charles Coulston Gillispie et al., eds., Complete Dictionary of Scientific Biography (New York: Scribner 2008 and earlier editions), 13:445–447; Alfred von Engel, “John Sealy Edward Townsend. 1868–1957,” Biographical Memoirs of Fellows of the Royal Society 3 (1957), 256–272; Mark McCartney, “John Sealy Edward Townsend,” in Mark McCartney and Andrew Whitaker, eds., Physicists of Ireland (Bristol: Institute of Physics Publishing, 2003), 168–175; Benoit Lelong, “Translating Ion Physics from Cambridge to Oxford: John Townsend and the Electrical Laboratory, 1900–24,” in Robert Fox and Graeme Gooday, eds., Physics in Oxford, 18391939 (Oxford: Oxford University Press, 2005); and Brebis Bleaney, “Two Oxford Science Professors, F. Soddy and J. S. E. Townsend,” Notes and Records of the Royal Society of London 56 (2002), 83–88.Google Scholar
  2. 2.
    Other accounts of these experiments and their aftermath (for the most part brief and, occasionally, misleading) include Jost Lemmerich, Science and Conscience. The Life of James Franck (transl. Ann M. Hentschel) (Stanford: Stanford University Press, 2011), esp. chap. 3; Helge Kragh, Niels Bohr and the Quantum Atom (Oxford: Oxford University Press, 2012), esp. 143–146; Josef Kuczera, Gustav Hertz (Leipzig: Teubner, 1985); John Lewis Heilbron, “A History of the Problem of Atomic Structure from the Discovery of the Electron to the Beginning of Quantum Mechanics,” PhD diss., University of California, Berkeley, 1964, esp. 313–319; J. L. Heilbron, “Lectures on the History of Atomic Physics,” in C. Weiner, ed., History of Twentieth Century Physics (New York: Academic Press, 1977), 40–107, esp. 75–77; Giora Hon, “Franck and Hertz versus Townsend: A Study of Two Types of Experimental Error,” Historical Studies in the Physical and Biological Sciences 20 (1989), 79–106; Giora Hon, “From Propagation to Structure: The Experimental Technique of Bombardment as a Contributing Factor to the Emerging Quantum Physics,” Physics in Perspective 5 (2003), 150–173; Giora Hon and Bernard R. Goldstein, “Centenary of the Franck-Hertz Experiments,” Annalen der Physik. 525 (2013), A179–A183; and for an especially thorough treatment, Henry Gilbert Small, “The Helium Atom in the Old Quantum Theory,” PhD diss., University of Wisconsin, 1971, esp. 45–56 and 214–257.Google Scholar
  3. 3.
    Hertz’s essay, “Zur Geschichte unserer Versuche über den Energieaustausch zwischen langsamen Elektronen und Atomen,” translated as “On the History of our Experiments on the Energy Exchange between Slow Electrons and Atoms” and cited hereafter as “History,” is in the James Franck Papers, Box 24, Folder 11, Special Collections Research Center, University of Chicago Library, hereafter cited as JFP. The correspondence between Hertz and Robert Platzman may be found there and in Box 24, Folder 3. In the translation, I have numbered the paragraphs for ease of reference.Google Scholar
  4. 4.
    Lemmerich, Franck (ref. 2), 307–309. See also Hertz to Franck, letter of January 5, 1964 and Franck to Hertz, letter of February 3, 1964, in JFP, Box 3, Folder 13.Google Scholar
  5. 5.
    R. W. Pohl, “Von den Studien- und Assistentenjahren James Francks,” Physikalische Blätter 28 (1972), 542–544. See also Thomas S. Kuhn, “Memorandum for Confidential File,” Emil Warburg file, Archives for the History of Quantum Physics (Niels Bohr Library and Archives, American Institute of Physics, College Park, MD; Walter Library, University of Minnesota; and elsewhere); hereafter cited as AHQP.Google Scholar
  6. 6.
    Interview of James Franck and Herta Sponer by Thomas S. Kuhn and Maria Goeppert Mayer, on 9–14 July 1962, AHQP, session 1, on 8–9.Google Scholar
  7. 7.
    See for example Gustav Hertz, “Quantensprünge und Isotopentrennung,” in Gert Lange and Joachim Mörke, eds., Wissenschaft im Interview (Leipzig: Urania-Verlag, 1978), 58–68, hereafter cited as 1978 Interview, on 59.Google Scholar
  8. 8.
    See, for example, Franck, AHQP interview (ref. 6), session 1, on 6–8; Wilhelm H. Westphal, “James Franck 80 Jahre (geb. 26.8.1882): Erinnerungen aus alten Zeiten,” Phys. Blät. 18 (1962), 370–371; Pohl, “Assistentenjahren” (ref. 5); Hertz, 1978 Interview (ref. 7), esp. 59–61.Google Scholar
  9. 9.
    J. J. Thomson, Conduction of Electricity through Gases (Cambridge: Cambridge University Press, 1903; 2nd ed., 1906; 3rd ed. with G. P. Thomson, 1928–1933).Google Scholar
  10. 10.
    For overviews, see Dong-Won Kim, Leadership and Creativity: A History of the Cavendish Laboratory, 18711919 (Dordrecht: Kluwer, 2002); Jaume Navarro, A History of the Electron: J. J. Thomson and G. P. Thomson (Cambridge: Cambridge University Press, 2012); George Paget Thomson, J. J. Thomson and the Cavendish Laboratory in His Day (London: Thomas Nelson and Sons, 1964), published in the U.S. as J. J. Thomson, Discoverer of the Electron (Garden City, NY: Doubleday, 1965); George E. Smith, “J. J. Thomson and the Electron, 1897–1899,” in Jed Z. Buchwald and Andrew Warwick, eds., Histories of the Electron: The Birth of Microphysics (Cambridge, MA: MIT Press, 2001), 21–76; Isobel Falconer, “Electrons and Cathode Rays: J. J. Thomson and the ‘Discovery of the Electron’,” British Journal for the History of Science 20 (1987), 241–276; E. A. Davis and I. J. Falconer, J. J. Thomson and the Discovery of the Electron (London: Taylor and Francis, 1997); and David L. Anderson, The Discovery of the Electron (New York: Van Nostrand, 1964).Google Scholar
  11. 11.
    Franck, AHQP interview (ref. 6), session 1, on 8; session 2, on 2.Google Scholar
  12. 12.
    See Thomson, Conduction of Electricity (ref. 9), esp. chap. 2 (1903 and 1906 editions) for discussion and references.Google Scholar
  13. 13.
    E. Rutherford, “The Velocity and Rate of Recombination of the Ions of Gases Exposed to Röntgen Radiation,” Philosophical Magazine 44 (1897), 422–440; E. Rutherford, “The Discharge of Electrification by Ultra-Violet Light,” Proceedings of the Cambridge Philosophical Society 9 (1898), 401–417.Google Scholar
  14. 14.
    John Zeleny, “The Velocity of the Ions Produced in Gases by Röntgen Rays,” Philosophical Transactions of the Royal Society of London, A 195 (1900), 193–234.Google Scholar
  15. 15.
    J. Franck, “Über die Beweglichkeit der Ladungsträger der Spitzenentladung,” Ann. Phys. 21 (1906), 972–1000. See also the descriptions in Robert Pohl’s unpublished and undated recollections, probably from the mid-1960s, in JFP, Box 24, Folder 19, and in Lemmerich, Franck (ref. 2), 19–21.Google Scholar
  16. 16.
    J. Franck and R. Pohl, “Eine Method zur Bestimmung der Ionenbeweglichkeit in kleinen Gasmengen” and “Die Ionenbeweglichkeit in Helium,” Verhandlungen der Deutschen Physikalischen Gesellschaft 9 (1907), 69–75 and 194–199; Zeleny, “Velocity” (ref. 14). See also J. Franck, “Bericht über Ionenbeweglichkeit,” Jahrbuch der Radioaktivität und Elektronik 9 (1912), 235–270.Google Scholar
  17. 17.
    J. Franck, “Über die Ionenbeweglichkeit in Argon und den Einfluss geringer Mengen Sauerstoffs” and “Über das Vorkommen freier Elektronen in chemisch trägen Gasen bei Atmosphärendruck,” Verh. D. Phys. Ges. 12 (1910), 291–298 and 613–620.Google Scholar
  18. 18.
    James Franck, “Emil Warburg zum Gedächtnis,” Die Naturwissenschaften 19 (1931), 993–997, esp. 994–995.Google Scholar
  19. 19.
    Franck, “Bericht” (ref. 16), 250, 259. Thomson mentioned these results in the third edition of his Conduction of Electricity (ref. 9), 1:133.Google Scholar
  20. 20.
    See Navarro, History of the Electron (ref. 10), esp. sec. 3.6; Thomson, Discoverer of the Electron (ref. 10); and the works cited in ref. 1.Google Scholar
  21. 21.
    Smith, “Thomson and the Electron” (ref. 10), 54, 74; Robert Andrews Millikan, The Electron (Chicago: University of Chicago Press, 1917) contains a detailed account of Townsend’s experiments.Google Scholar
  22. 22.
    Gyeong Soon Im, “The Formation and Development of the Ramsauer Effect,” Historical Studies in the Physical and Biological Sciences 25 (1995), 269–300.Google Scholar
  23. 23.
    See Bleaney, “Professors” (ref. 1), 87; Lelong, “Translating Ion Physics” (ref. 1), 229; and for a more detailed account, Hon, “Franck and Hertz versus Townsend” (ref. 2; note caveat).Google Scholar
  24. 24.
    J. Franck and W. Westphal, “Über doppelt geladene Gasionen” and “Über die Ladung von Gasionen,” Verh. D. Phys. Ges. 11 (1909), 146–154 and 276–280.Google Scholar
  25. 25.
    J. S. Townsend, “The Conductivity Produced in Gases by the Motion of Negatively-charged Ions,” Nature 62 (1900), 340–341; John S. Townsend, “The Conductivity Produced in Gases by the Motion of Negatively charged Ions,” Phil. Mag. 1 (1901), 198–227; John S. Townsend, The Theory of Ionization of Gases by Collision (London: Constable and Company, 1910). Franck and Hertz cited Townsend’s book almost exclusively in their discussion of his work.Google Scholar
  26. 26.
    J. J. Thomson and E. Rutherford, “On the Passage of Electricity through Gases Exposed to Röntgen Rays,” Phil. Mag. 42 (1896), 392–407. According to G. P. Thomson, Discoverer of the Electron (ref. 10), 92ff., this paper set the stage for the research on conduction in gases that Thomson and his students at the Cavendish conducted for the next several years. See also Smith, “Thomson and the Electron” (ref. 10), 64.Google Scholar
  27. 27.
    J. S. Townsend, Electricity in Gases (Oxford: Oxford University Press, 1915), 261.Google Scholar
  28. 28.
    Townsend, Theory of Ionization (ref. 25). Chapter 1 outlines his experiments and theory. His values for ionization potentials appear on 24–27.Google Scholar
  29. 29.
    E. Rutherford and R. K. McClung, “Energy of Röntgen and Becquerel Rays and the Energy Required to Produce an Ion in Gases,” Proceedings of the Royal Society of London. 67 (1900), 245–250, and “Energy of Röntgen and Becquerel Rays, and the Energy Required to Produce an Ion in Gases,” Phil. Trans. A196 (1901), 25–59.Google Scholar
  30. 30.
    P. Lenard, “Ueber die Lichtelektrische Wirkung,” Ann. Phys. 8 (1902), 149–198, esp. 188–198.Google Scholar
  31. 31.
    Townsend, Theory of Ionization (ref. 25), 28–29.Google Scholar
  32. 32.
    For later perspectives on the strengths and limitations of Townsend’s work on ionization by collision, see Leonard B. Loeb, The Kinetic Theory of Gases (2nd ed., New York: McGraw-Hill, 1934), reprinted with a new introduction (New York: Dover, 1962), chap. 11. See also interview of Sir George Paget Thomson by John L. Heilbron on June 20, 1963, AHQP.Google Scholar
  33. 33.
    James Franck, “Transformation of Kinetic Energy of Free Electrons into Excitation Energy of Atoms by Impacts,” in Nobel Lectures, 19221941 (Amsterdam: Elsevier, 1964), 99–106, and readily available on-line.Google Scholar
  34. 34.
    Interview of Gustav Hertz by Théo Kahan and John L. Heilbron on May 14–15, 1963, AHQP, session 1, on 2–3. See also Hertz, 1978 Interview (ref. 7), 60.Google Scholar
  35. 35.
    Franck, AHQP interview (ref. 6), session 2, on 4; Hertz, AHQP interview (ref. 34), session 1, esp. 7, 12, 17, 22; Hertz, “History” (ref. 3), ¶ 19; Gustav Hertz, “Memories of James Franck and the Electron Scattering Experiments,” 18th Lindau Laureate Meeting, 1968, early in the talk. Both the talk and unpaginated German and English transcripts are available at, accessed July 19, 2014.
  36. 36.
    Franck, AHQP interview (ref. 6), session 2, on 4; Hertz, Lindau lecture (ref. 35), early in the talk.Google Scholar
  37. 37.
    Hertz, AHQP interview (ref. 34), session 1, on 4–5; G. Hertz, “Aus den Anfangsjahren der Quantenphysik,” in V. A. Ambarzumjan and Gustav Hertz, eds., Festvorträge der wissenschaftlichen Konferenz der Akademie anläßlich des 275. Akademiejubiläums (Berlin: Akademie-Verlag, 1975), 17–37, on 29. See also Hertz, “History” (ref. 3), ¶ 5; and Hertz, 1978 Interview (ref. 7), 58.Google Scholar
  38. 38.
    J. N. Collie and William Ramsay, “On the Behaviour of Argon and Helium When Submitted to the Electric Discharge,” Proc. Roy. Soc. 59 (1896), 257–270; Frederick Soddy and Thomas D. MacKenzie, “The Electric Discharge in Monatomic Gases,” Proc. Roy. Soc. 80 (1908), 92–109.Google Scholar
  39. 39.
    J. Franck and G. Hertz, “Über Zusammenstösse zwischen Gasmolekülen und langsamen Elektronen,” Verh. D. Phys. Ges. 15 (1913), 373–390, esp. 388.Google Scholar
  40. 40.
    Hertz, “Anfangsjahren” (ref. 37), 29. See also Hertz, AHQP interview (ref. 34), session 1, esp. 4–5; Hertz, Lindau lecture (ref. 35), early in the talk; Hertz, 1978 Interview (ref. 7), 58.Google Scholar
  41. 41.
    Franck, AHQP interview (ref. 6), session 1, on 6–7, 10; Hertz, AHQP interview (ref. 34), session 1, on 8.Google Scholar
  42. 42.
    J. Franck and G. Hertz, “Über einen Zusammenhang zwischen Quantenhypothese und Ionisierungsspannung,” Verh. D. Phys. Ges. 13 (1911), 967–971.Google Scholar
  43. 43.
    Arthur Llwelyn Hughes, “Report on Photoelectricity,” Bulletin of the National Research Council 2 (1921), 83–169, esp. 102 and 115–118.Google Scholar
  44. 44.
    Thomas S. Kuhn, “Notes by T. S. Kuhn on unrecorded conversations,” Franck interview file, AHQP (ref. 6); see also session 2, on 1.Google Scholar
  45. 45.
    Hertz, AHQP interview (ref. 34), session 1, on 4.Google Scholar
  46. 46.
    J. Franck and G. Hertz, “Über eine Methode zur direkten Messung der mittleren freien Weglänge von Gasmolekülen. I.,” Verh. D. Phys. Ges. 14 (1912), 596–604.Google Scholar
  47. 47.
    Hertz, AHQP interview (ref. 34), session 1, on 5–6.Google Scholar
  48. 48.
    J. Franck and G. Hertz, “Messung der Ionisierungsspannung in verschiedenen Gasen,” Verh. D. Phys. Ges. 15 (1913), 34–44.Google Scholar
  49. 49.
    Lenard, “Lichtelektrische” (ref. 30).Google Scholar
  50. 50.
    O. v. Baeyer, “Über langsame Kathodenstrahlen,” Verh. D. Phys. Ges. 10 (1908), 96–114.Google Scholar
  51. 51.
    They describe this effect more fully in J. Franck and G. Hertz, “Notiz über Bildung von Doppelschichten,” Verh. D. Phys. Ges. 15 (1913), 391–393.Google Scholar
  52. 52.
    Walther Gerlach, “Das Vakuum in Geistesgeschichte, Naturwissenschaft und Technik,” Phys. Blät. 13 (1967), 97–106; Hinrich Henning, “100 Jahre HV-Pumpe von Wolfgang Gaede,” Vakuum in Forschung und Praxis 17 (2005), 280–281; Paul A. Redhead (ed.), Vacuum Science and Technology: Pioneers of the 20th century (New York: AIP Press, 1994); Karl Jousten, ed., Handbook of Vacuum Technology (Weinheim: Wiley VCH, 2008), chap. 1; Saul Dushman, Production and Measurement of High Vacuum (Schenectady: General Electric, 1922).Google Scholar
  53. 53.
    Hertz, AHQP interview (ref. 34), session 1, on 6.Google Scholar
  54. 54.
    Franck gave this explanation in J. Franck and P. Jordan, Anregung von Quantensprüngen durch Stösse (Berlin: Springer, 1926), 82; see also Hertz, “History” (ref. 3), ¶ 6.Google Scholar
  55. 55.
    Franck and Hertz, “Ionisierungsspannung” (ref. 48), 41. See also Karl T. Compton, “Critical Potentials. Part I. Critical Potential Method,” Bul. Nat. Res. Coun. 9 (1924), 3–60, on 4.Google Scholar
  56. 56.
    Franck and Hertz apologized for overlooking Stark’s work in their 1911 paper (ref. 42) in J. Franck and G. Hertz, “Bemerkung zu unserer Notiz über einen Zusammenhang zwischen Ionisierungsspannung und Quantenhypothese,” Verh. D. Phys. Ges. 14 (1912), 167–168.Google Scholar
  57. 57.
    Arnold Sommerfeld, “Die Bedeutung des Wirkungsquantums für unperiodisches Molekularprozesses” and “Zusätze zur Deutschen Ausgabe (Juli 1913),” in A. Eucken, ed. and transl., Die Theorie der Strahlung und der Quanten (Halle: W. Knapp, 1914), 252–317, esp. 291–294, 298–300. See also Suman Seth, Crafting the Quantum: Arnold Sommerfeld and the Practice of Theory, 18901926 (Cambridge, MA: MIT Press, 2010), esp. 139–156; Michael Eckert, Arnold Sommerfeld: Science, Life and Turbulent Times 18681951 (New York: Springer, 2013), esp. chap. 6; and Small, “Helium Atom” (ref. 2), 56–58.Google Scholar
  58. 58.
    Franck and Hertz, “Zusammenstösse” (ref. 39).Google Scholar
  59. 59.
    Franck and Hertz, “Notiz” (ref. 51).Google Scholar
  60. 60.
    J. Franck and G. Hertz, “Über Zusammenstösse zwischen Gasmolekülen und langsamen Elektronen. II,” Verh. D. Phys. Ges. 15 (1913), 613–620.Google Scholar
  61. 61.
    Franck and Jordan, Anregung (ref. 54), 33–44. See also Franck, Nobel Lecture (ref. 33), 101.Google Scholar
  62. 62.
    G. Hertz, “Über den Energteaustausch bei Zusammenstössen zwischen langsamen Elektronen und Gasmolekülen,” Verh. D. Phys. Ges. 19 (1917), 268–288. This paper was Hertz’s Habilitationsschrift, successful completion of which allowed him to teach at German universities.Google Scholar
  63. 63.
    J. Franck and G. Hertz, “Über einen Zusammenhang zwischen Stossionisation und Elektronenaffinität,” Verh. D. Phys. Ges. 15 (1913), 929–934, on 932; also published in Physikalische Zeitschrift 14 (1913), 1115–1117. See also two letters from Franck to Robert Pohl, one undated from summer 1913, the other 16 August 1913, in Florian Ebner, ed., James FranckRobert Wichard Pohl, Briefwechsel 19061964 (Munich: Preprint 8, Deutsches Museum, 2013), Nos. 38 and 39, 73–77.Google Scholar
  64. 64.
    J. Franck and G. Hertz, “Zur Theorie der Stossionisation,” Verh. D. Phys. Ges. 16 (1914), 12–19.Google Scholar
  65. 65.
    Hertz, AHQP interview (ref. 34), session 1, on 12.Google Scholar
  66. 66.
    See for example Franck and Jordan, Anregung (ref. 54), 44–50; and Loeb, Kinetic Theory (ref. 32), chap. 11.Google Scholar
  67. 67.
    J. Franck and G. Hertz, “Über Zusammenstösse zwischen Elektronen und den Molekülen des Quecksilberdampfes und die Ionisierungsspannung desselben,” Verh. D. Phys. Ges. 16 (1914), 457–467.Google Scholar
  68. 68.
    For an early example, see B. H. Newman, “Note on the Ionization Potential of Mercury Vapour,” Phil. Mag. 28 (1914), 753–756.Google Scholar
  69. 69.
    Hertz, Lindau lecture (ref. 35), about two thirds of the way through the talk.Google Scholar
  70. 70.
    For a thorough review of these methods through the mid-1920s, see Compton, “Critical Potentials” (ref. 55).Google Scholar
  71. 71.
    Hertz, Lindau lecture (ref. 35), about two thirds of the way through the talk.Google Scholar
  72. 72.
    Franck, AHQP interview (ref. 6), session 2, on 2 and session 4, on 5–7; Hertz, AHQP interview (ref. 34), session 1, on 20.Google Scholar
  73. 73.
    See, accessed July 19, 2014.
  74. 74.
    For sodium, see the last page of R. W. Wood, “A Quantitative Determination of the Anomalous Dispersion of Sodium Vapor in the Visible and Ultra-Violet Regions,” Proceedings of the American Academy of Arts and Sciences 40 (1904), 365–396; also published in Phil. Mag. 8 (1904), 293–331; and, in more detail, “The Fluorescence of Sodium Vapour and the Resonance Radiation of Electrons,” Phil. Mag. 10 (1904), 513–525. For mercury, see R. W. Wood, “The Selective Reflexion of Monochromatic Light by Mercury Vapour,” Phil. Mag. 18 (1909), 187–195. See also the discussions in his textbook Physical Optics (London and New York: MacMillan, 1st ed., 1905; 2nd ed., 1911; 3rd ed., 1934).Google Scholar
  75. 75.
    J. Franck and G. Hertz, “Über die Erregung der Quecksilberresonanzlinie 253,6 μμ durch Elektronenstösse,” Verh. D. Phys. Ges. 16 (1914), 512–517.Google Scholar
  76. 76.
    John L. Heilbron and Thomas S. Kuhn, “The Genesis of the Bohr Atom,” Historical Studies in the Physical Sciences 1 (1969), 211–290, esp. 263–264; Heilbron, “Atomic Structure” (ref. 2), 176–185; Walther Gerlach, Die experimentellen Grundlagen der Quantentheorie (Braunschweig/Wiesbaden: Vieweg, 1921), 5.Google Scholar
  77. 77.
    Franck and Hertz, “Zusammenstösse” (ref. 67), 466.Google Scholar
  78. 78.
    Franck and Hertz, “Theorie” (ref. 64), 13–14.Google Scholar
  79. 79.
    Franck and Hertz, “Ionisierungsspannung” (ref. 48), 934.Google Scholar
  80. 80.
    J. Franck and W. Westphal, “Über eine Beeinflussung der Stossionisation durch Fluoreszenz,” Verh. D. Phys. Ges. 14 (1912), 159–166.Google Scholar
  81. 81.
    Franck and Jordan, Anregung (ref. 54), chap. 4.Google Scholar
  82. 82.
    Franck and Hertz, “Zusammenhang” (ref. 42), 970.Google Scholar
  83. 83.
    Hertz, AHQP interview (ref. 34), session 1, on 14–15. See also Franck and Jordan, Anregung (ref. 54), 119–120; J. Franck, “Über Lichtanregung und Ionisation von Atomen und Molekülen durch Stöße langsamer Elektronen” (in 4 parts), Phys. Zeit. 22 (1921), 388–391, 409–414, 441–448, 466–471; on 443.Google Scholar
  84. 84.
    Franck and Westphal, “Beeinflussung” (ref. 80).Google Scholar
  85. 85.
    Franck, AHQP interview (ref. 6), session 2, on 1.Google Scholar
  86. 86.
    E. Gehrcke and R. Seeliger, “Über das Leuchten der Gase unter dem Einfluß von Kathodenstrahlen, I & II,” Verh. D. Phys. Ges. 14 (1912), 335–343, 1023–1031; H. Rau, “Über die Lichterregung durch langsame Kathodenstrahlen,” Physikalisch-Medicinischen Gesellschaft zu Wurzbürg, Sitzungsberichte (1914), 20–27. See also Small, “Helium Atom” (ref. 2), 210–214.Google Scholar
  87. 87.
    Gerlach, Grundlagen (ref. 76), 16.Google Scholar
  88. 88.
    See also Compton, “Critical Potentials” (ref. 55); Hon, “Franck and Hertz versus Townsend” (ref. 2); and Small, “Helium Atom” (ref. 2).Google Scholar
  89. 89.
    Otto Hahn, My Life: The Autobiography of a Scientist (New York: Herder and Herder, 1970), 118–121; Dietrich Stoltzenberg, Fritz Haber, Chemiker, Nobelpreisträger, Deutscher, Jude (Weinheim: VCH, 1994), 246–247; Lemmerich, Franck (ref. 2), 54–60; Franck, AHQP interview (ref. 6), session 2, esp. 8, 11–12.Google Scholar
  90. 90.
    J. Franck and G. Hertz, “Über die relative Intensität der Gasspektra bei der Glimmentladung in Gasgemischen,” Verh. D. Phys. Ges. 18 (1916), 213–220.Google Scholar
  91. 91.
    J. Franck and G. Hertz, “Über Kinetik von Elektronen und Ionen in Gasen,” Phys. Zeit. 17 (1916), 409–416, 430–440. See also Small, “Helium Atom” (ref. 2), 237–242.Google Scholar
  92. 92.
    Alfred Fowler, Report on Series in Line Spectra (London: Fleetway Press, 1922), 23–24; Kragh, Niels Bohr (ref. 2), 57, 66. See also the first edition of Floyd K. Richtmyer, Introduction to Modern Physics (New York: McGraw-Hill, 1928), chap. IX.Google Scholar
  93. 93.
    Niels Bohr, “On the Quantum Theory of Radiation and the Structure of the Atom,” Phil. Mag. 30 (1915), 394–415, reprinted in Ulrich Hoyer, ed., Niels Bohr Collected Works (Amsterdam: North Holland, 1981), 2:389–413, esp. 410–411.Google Scholar
  94. 94.
    Hendrik J. van der Bijl, “Note on the Ionizing Potential of Metallic Vapors,” Phys. Rev. 9 (1917), 173–175 and “Theoretical Considerations Concerning Ionization and Single-Lined Spectra,” Phys. Rev. 10 (1917), 546–556. For more on van der Bijl, see B. F. J. Schonland, “Hendrik Johannes van der Bijl, 1887–1948,” Obituary Notices of Fellows of the Royal Society 7 (1950), 26–34.Google Scholar
  95. 95.
    Franck and Hertz, “Kinetik” (ref. 91), 438.Google Scholar
  96. 96.
    Franck, AHQP interview (ref. 6), session 2, esp. 8, 11; Hertz, AHQP interview (ref. 34), session 1, on 18.Google Scholar
  97. 97.
    Franck, AHQP interview (ref. 6), session 3, on 1.Google Scholar
  98. 98.
    John T. Tate, “The Low Potential Discharge Spectrum of Mercury Vapor in Relation to Ionization Potentials,” Phys. Rev. 7 (1916), 686–687. See also John T. Tate, “The Passage of Low Speed Electrons through Mercury Vapor and the Ionizing Potential of Mercury Vapor,” Phys. Rev. 10 (1917), 81–83. For more on Tate, see Alfred O. C. Nier and John H. Van Vleck, “John Torrence Tate, 1889–1950,” Biographical Memoirs of the National Academy of Science 47 (1975), 460–485.Google Scholar
  99. 99.
    See Small, “Helium Atom” (ref. 2), 216–222.Google Scholar
  100. 100.
    J. C. McLennan and J. P. Henderson, “Ionisation Potentials of Mercury, Cadmium, and Zinc, and the Single- and Many-Lined Spectra of these Elements,” Proc. Roy. Soc. 91 (1915), 485–491. For Thomson, see J. J. Thomson, Rays of Positive Electricity and Their Application to Chemical Analysis (London: Longmans, Green, 1913), 49–50.Google Scholar
  101. 101.
    J. C. McLennan, “On the Single-Line Spectra of Magnesium and other Metals and their Ionising Potentials,” Proc. Roy. Soc. 92 (1916), 305–312.Google Scholar
  102. 102.
    J. C. McLennan and David A. Keys, “On the Ionisation of Metallic Vapours in Flames,” Proc. Roy. Soc. 92 (1916), 591–608, esp. 608.Google Scholar
  103. 103.
    J. C. McLennan, “On the Origin of Spectra (Recent Progress),” British Association for the Advancement of Science, Report of the Ninety-First Meeting, Liverpool, 1923 (London: Murray, 1924), 25–58.Google Scholar
  104. 104.
    T. C. Hebb, “The Single-Lined and Many-Lined Spectrum of Mercury,” Phys. Rev. 9 (1917), 371–377.Google Scholar
  105. 105.
    R. A. Millikan, “Theoretical Considerations Relating to the Single-Lined and the Many-Lined Spectrum of Mercury,” Phys. Rev. 9 (1917), 378–382.Google Scholar
  106. 106.
    Bergen Davis and F. S. Goucher, “Ionization and Excitation of Radiation by Electron Impact in Mercury Vapor and Hydrogen,” Phys. Rev. 10 (1917), 101–115.Google Scholar
  107. 107.
    For more on Davis, see Harold W. Webb, “Bergen Davis 1869–1958,” Bio. Mem. Nat. Acad. 34 (1960), 65–82.Google Scholar
  108. 108.
    F. S. Goucher, “Ionization by Impact in Mercury Vapor and Other Gases,” Phys. Rev. 8 (1916), 561–573.Google Scholar
  109. 109.
    See also the description in Compton, “Critical Potentials” (ref. 55), 12–14.Google Scholar
  110. 110.
    J. Franck and G. Hertz, “Die Bestätigung der Bohrschen Atomtheorie im optischen Spektrum durch Untersuchungen der unelastischen Zusammenstöße langsamer Elektronen mit Gasmolekülen,” Phys. Zeit. 20 (1919), 132–143. See also Hertz, AHQP interview (ref. 34), session 1, on 22.Google Scholar
  111. 111.
    Hertz, AHQP interview (ref. 34), session 1, esp. 22, 25–26. See also Christian Kleint, “Gustav Hertz—zur 100. Wiederkehr seines Geburtstages,” Phys. Blät. 43 (1987), 255–257, esp. 256; and Kuczera, Gustav Hertz (ref. 2), 35.Google Scholar
  112. 112.
    See Hertz, AHQP interview file (ref. 34) for a partial bibliography. See also the many references to Hertz’s later work in Franck and Jordan, Anregung (ref. 54).Google Scholar
  113. 113.
    Max Born, My Life: Recollections of a Nobel Laureate (New York: Scribner, 1978), 188.Google Scholar
  114. 114.
    Fritz Reiche, “Die Quantentheorie. Ihr Uhrsprung und ihre Entwicklung” and Paul S. Epstein, “Anwendungen der Quantenlehre in der Theorie der Serienspektren,” Die Naturwissenschaften 6 (1918), 213–230 and 230–253. See also Clayton A. Gearhart, “Fritz Reiche’s 1921 Quantum Theory Textbook,” in Massimiliano Badino and Jaume Navarro, eds., Research and Pedagogy: A History of Early Quantum Physics through its Textbooks (Berlin: Edition Open Access, 2013), 101–116.Google Scholar
  115. 115.
    See Small, “Helium Atom” (ref. 2), esp. 208–258.Google Scholar
  116. 116.
    Ibid., 297–302; Lemmerich, Franck (ref. 2), 64–69. See also the discussions in Franck and Jordan, “Anregung” (ref. 54), index.Google Scholar
  117. 117.
    For a more complete discussion than I give here and for references to works not cited in this paragraph, see Kragh, Niels Bohr (ref. 2), 122–128.Google Scholar
  118. 118.
    R. Seeliger, “Einige allgemeine Bemerkung zur Theorie der Stoßionisation,” Jahrb. Radioakt, Elekt. 10 (1913), 431–445, on 434; cited in Franck and Hertz, “Quecksilberdampfes” (ref. 67), 464.Google Scholar
  119. 119.
    Interview of Robert Wichard Pohl by Thomas S. Kuhn and Friedrich Hund on 25 June 1963, AHQP, 13–16.Google Scholar
  120. 120.
    Lemmerich, Franck (ref. 2), esp. chap. 4; Born, My Life (ref. 113), 211.Google Scholar
  121. 121.
    Lemmerich, Franck (ref. 2), 299, 303.Google Scholar
  122. 122.
    Gerald Holton, “On the Recent Past of Physics,” American Journal of Physics 29 (1961), 805–810, esp. 808; Franck, AHQP interview (ref. 6), session 1, on 12; session 2, on 6, 8; session 3, on 16; session 4, on 5, 7.Google Scholar
  123. 123.
    Franck to Thomas Kuhn, letter of 16 November 1962, in Franck’s AHQP interview file (ref. 6).Google Scholar
  124. 124.
    Franck, Nobel Lecture (ref. 33), 106.Google Scholar
  125. 125.
    Franck and Jordan, Anregung (ref. 54), 83.Google Scholar
  126. 126.
    James Franck, “Niels Bohrs Persönlichkeit,” Die Naturwissenschaften 50 (1963), 341–343.Google Scholar
  127. 127.
    Gustav Hertz, “Die Bedeutung der Planckschen Quantentheorie für die experimentelle Physik,” in Armin Beck, ed., Max Planck zum Gedenken (Berlin: Akademie-Verlag, 1959), 29–41, on 39. See also the more detailed account in Hertz, “Anfangsjahren” (ref. 37), 27–28. An essay two years earlier gave a brief summary of their 1914 experiments but did not even mention them by name, much less their mistaking excitation for ionization. See G. Hertz, “Die Grundlagen der Atomphysik” in Gustav Hertz, ed., Grundlagen und Arbeitsmethoden der Kernphysik (Berlin: Akademie-Verlag, 1957), 1–39.Google Scholar
  128. 128.
    Hertz, AHQP interview (ref. 34), session 1, on 16.Google Scholar
  129. 129.
    Gustav Hertz, “James Franck,” Ann. Phys. 15 (1965), 1–4, esp. 3.Google Scholar
  130. 130.
    Hertz, Lindau lecture (ref. 35).Google Scholar
  131. 131.
    Ibid., early in the talk. See also for example Hertz, AHQP interview (ref. 34), session 1, on 16, 22.Google Scholar
  132. 132.
    Hertz, “Anfangsjahren” (ref. 37), 28; see also Hertz, 1978 Interview (ref. 7).Google Scholar
  133. 133.
    For another statement to this effect, apparently referring to 1916, see Hertz, AHQP interview (ref. 34), session 1, on 20.Google Scholar

Copyright information

© Springer Basel 2014

Authors and Affiliations

  1. 1.Saint CloudUSA

Personalised recommendations