Geiger, Hans (Johannes) Wilhelm

(b. Neustadt an der Haardt [now Neustadt an der Weinstrasse], Rheinland-Pfalz, Germany. 30 September 1882; d. Potsdam, Germany, 24 September 1945)

physics.

Geiger developed a variety of instruments and techniques for the detection and counting of individual charged particles. He was the eldest of the five children of Wilhelm Ludwig Geiger, professor of philology at Erlangen from 1891 to 1920. His only brother, Rudolf, became professor of meteorology at Munich. Geiger passed his Abitur at the Erlangen Gymnasium in 1901. After a brief period of military service he studied physics both at Munich and at Erlangen. He took his preliminary examination in 1904 and then began his research under Eilhard Wiedemann. In July 1906 Geiger defended his inaugural dissertation and received his doctorate from the University of Erlangen. He then took a position in England, followed by a series of appointments in Germany.

Geiger married Elisabeth Heffter in 1920; they had three sons. He completed his Habilitationsschrift at Berlin in 1924. Geiger was awarded the Hughes Medal by the Royal Society on 30 November 1929 “for his invention and development of methods of counting alpha and beta particles,”¹ and the Duddell Medal by the Physical Society (London) in 1938 for his contributions to scientific instrumentation. Geiger was elected to the Leopoldina in 1935 and to the Preussische Akademie der Wissenschaften in 1937.

Geiger was a perfectionist, always trying to obtain the most from both his students and his experiments. His enthusiastic and warmhearted nature inspired others to emulate his methods and share his goals. He was a talented lecturer, popular with both his colleagues and the public.

In 1906 Geiger was assistant to Arthur Schuster at Manchester. Ernest Rutherford, who succeeded Schuster in 1907, persuaded Geiger to remain at Manchester and continue research on radioactivity. In 1908, working out the probability variations and statistical error factor, Geiger extended the experimental confirmation of the 1905 theoretically predicted “Schweidler fluctuations” for the case of radio active disintegrations.

In 1908 Geiger and Rutherford investigated the charge and nature of the α particle. They devised an electrical technique in order to count the individual α particles and compare results with those obtained by Erich Regener, who used the scintillation technique. Their ionization chamber was a cylinder at low pressure with a thin wire stretched coaxially (Fig. 1). The wall of the cylinder had an entrance window at one end and was at high negative potential to the wire. An α particle entering parallel to the wire generated a secondary avalanche, according to the 1900 collision principle of John S. Townsend, multiplying the primary ionization effect a thousandfold. The resulting voltage step on the central wire was measured by a sensitive electrometer. With this proto-“Geiger counter” they estimated that the total number of α particles emitted per second from the radium C (actually radium C´) present in one gram of radium in equilibrium was 3.4 × 10¹⁰. From this value and a determination of the total charge in a beam of α particles, they established that the a particle was doubly charged. This led directly to the confirmation by Rutherford and T. Royds that α particles were doubly charged helium atoms.

The beam of α particles was observed to spread. Geiger investigated this scattering effect and was joined in 1909 by Ernest Marsden. Using a scintillation detector, they observed the number of particles scattered at various angles of incidence. They detected α particles reflected at angles sufficiently large to make inadequate a statistical interpretation based upon multiple scattering. On preliminary evidence Rutherford was led to propose in 1911 that this effect was due to single scattering from compact nuclei. He theoretically predicted the behavior of a set of scattering parameters based upon a nuclear model of the atom. Geiger and Marsden undertook a further series of experiments and verified the predicted behavior of these parameters by July 1912.²

In 1910 Geiger examined α particles from a variety of radioactive substances and noted a linear relationship between the maximum range and the third power of the velocity of expulsion. Following up the 1907 suggestion of Rutherford, Geiger and John Michael Nuttall empirically established in 1911–1912 what seemed an essentially linear relationship between the half-value period, on the one hand, and the maximum range or energy of disintegration, on the other, for α particles from various materials. Later, in 1921, Geiger revised this empirical Geiger-Nuttall rule, noting that actinium-X did not fit the

straight-line curve, and in 1928 George Gamow and others partially superseded this empirical rule altogether with a physical explanation of α disintegration in terms of the probability of α penetration of potential barriers.

In October 1912 Geiger, having turned down a call to Tübingen, took up the newly established position of director of the laboratory for radium research at the Physikalisch-Technische Reichsanstalt in Berlin. In addition to measuring radium samples, he continued experiments on the counting of α particles. Varying the form and dimensions of the central electrode, he found an arrangement which came to be known as the Spitzenzähler or “point counter,” since “the whole working of the apparatus depends on the point of the needle” (Fig. 2).³ The great advantage of this device was that in addition to α particles, it could, for the first time, count β particles as well as other types of radiation. Geiger noted that at ordinary pressure the size of the voltage step was proportional to the intensity of the incident radiation, whereas “the deflections at low pressure are all equal and independent of the intensity of the primary ionization.”⁴

In November 1913 Geiger was joined by Walther Bothe, who investigated α scattering, and by James Chadwick, who counted β particles. In 1914 Chad wick was led by his investigations to note the presence of the continuous β spectrum in addition to the known line spectrum.

After the war Geiger returned to the Reichsanstalt. The 1924 statistical interpretation by Niels Bohr, H. A. Kramers, and J. C. Slater of the 1923 Compton effect stimulated Bothe and Geiger to devise, by that June, a technique to test its validity.⁵ Using two Spilzenähler in what was most likely the first coincidence experiment,⁶ completed by April 1925, they noted that approximately every eleventh captured quantum was coincident to within 10-⁴ seconds of it recoiled electron.⁷ This result, while unintelligible on the statistical interpretation, reconfirmed the validity of classic conservation principles for single atomic events.

In 1925 Geiger took his first teaching position as professor of physics at the University of Kiel. In addition to teaching and directing a large research team at the Institute of Physics, Geiger developed with Walther Müller the counting device for which his name is best known. The Geiger-Müller counter was based upon the 1908 coaxial-wire principle (see Figure 1) and followed directly from the clarification by Geiger in July 1928 of an anomaly which Müller had encountered in his research.⁸ The sensitivity of the counter was greatly improved so that it normally had to be shielded from background radiation. The recovery time was reduced through rapid quenching of the secondary avalanche. The construction of the central wire was improved so as to extend the operational lifetime for periods of months, and the signal could be amplified so as to trigger a mechanical register. In general, the device was designed to be compact, portable, and functional, and thus to meet a variety of laboratory requirements in particle detection and counting. The gradual production of these practical Geiger-Müller counters from 1928 marks the introduction of modern electrical devices into radiation research.

In October 1929 Geiger accepted a call to the University of Tübingen as professor of physics and director of research at the Institute of Physics. He continued to improve the counter, which by 1928 had already been extended in application to the study of canal rays. After noting that counters placed in separate rooms at the Institute periodically registered simultaneous bursts of radiation—the first detection of cosmic ray showers⁹—in 1931 Geiger refused a call to Lenard’s chair at Heidelberg and began a series of investigations on cosmic radiation which he continued throughout the remainder of his career.

In October 1936 Geiger accepted the chair of physics at the Technische Hochschule in Berlin. While directing a large research team studying artificial radioactivity and the products of nuclear fission, he continued to make full use of his counting device, with which he had made possible the investigation of cosmic radiation. In 1937 Geiger and Otto Zeiller used nine such counting tubes in a circular arrangement to determine the angular distribution of a cosmic ray shower. His last lecture, given in April 1942, was on cosmic rays.

The war years brought a severe recurrence of a rheumatic condition, suffered during his front-line duty as an artillery officer in World War I, and contributed to his increasing absence from the Institute. However, it did not prevent him from going to the Institute even during 1944.¹⁰ He also continued as editor of Zeirschrift für Physik, which he had taken over from Karl Scheel in 1936.¹¹

In June 1945 Geiger was forced to abandon his home and possessions in Babelsberg and flee to nearby Potsdam, where he died shortly afterward.

NOTES

1.Nature, 124 (1929), 767.

2. Hans Geiger and Ernest Marsden, “Die Zerstreuungsgesetze der alpha Strahlen bei grossen Ablenkungswinkeln,” in Sitzungberichte der Akodemie der Wissenschaften zu Wien, Math.-nat. Kl., Abt. II-a. 121 (1912), 2361–2390.

3. Geiger letter to Ernest Rutherford, 5 May 1913; Cambridge University Library Add. MSS 7653/G31.

4.Ibid.

5. Walther Bothe and Hans Geiger, “Ein Weg zur experimentellen Nachprüfung der Theorie von Bohr, Kramers und Slater,” in Zeitschrift für Physik, 26 (1924), 44.

6. Professor Walther Gerlach informed me privately in Apr. 1971 that this was the first coincidence experiment.

7. Walther Bothe and Hans Geiger, “Über das Wesen des Comptoneffekts; ein experimenteller Beitrag zur Theorie der Strahlung.” in Zeitschrift für Physik, 32 (1925), 639.

8. C. Schmidl-Schönbeck, 300 Jahre Kieler Universirät, p. 142.

9. Private confirmation by Walther Gerlach, Apr. 1971.

10. Private confirmation by Walther Gerlach, Apr. 1971.

11. Geiger was editor for eight years and issued the twenty vols. from 104 (1957) 123 (1944); the partially complete last vol. was terminated in Oct. 1944.

BIBLIOGRAPHY

I. Original Works. A nearly complete bibliography of Geiger’s writings is in M. von Laue, “Nachruf auf Hans Geiger,” in Jahrbucvh der Deutsxhen Akademre der Wissenschaften zu Berlin: 1946–1949 (1950), pp. 150–158. In this bibliography, no. 46 should read “(1924)” instead of “(1927)” and the pagination “of no. 61 is pp. 109–122. Besides the articles and scientific papers in Laue’s bibliography, Geiger wrote “Erscheinungen bei sehr starken Strömen in Entladungsrönren,” in Comptes rendus du Premier Congrès International pour l’Étude de la Radiologie ei de l’Ionisation, tenu a Liège, Septembre 1905 (Brussels, 1906), pp. 41–45, also published separately (Erlangen, 1905), an abstract of which is in Physikalische Zeitschrift, 6 (l905), 913–914; “Demonstrationsversuch zur Erläuterung der Temperaturverhältnisse in den Schichten des positiven Lichtes,” in Verhandlung der Deutschen phvsikalischen Gesellschaft, 8 (1906), 116–118, also published separately (Brunswick, 1906); “Die Kernstruktur der Atome und ihre experimentelle Begründung,” in Zeitschrift des Vereins deutscher Ingenieure, 66 (1922), 221–225; “Der Einfluss der Atompgysik auf unser Weltbild,” in Deutschland in der Wende der Zeiten, the open lectures for the summer semester of 1933 at the University of Tübingen (Stuttgart Berlin. 1934), pp. 107–121; and “Memories of Rutherford in Manchester,” in Nature, 141 (1938), 244, as well as “Some Reminiscences of Rutherford During His Time in Manchester,” in J. Chadwick, ed., The Collected Papers of Lord Rutherford, II(London, 1963), 295–298.

With Walter Makower, Geiger published Practical Measurements in Radiao-Activity (London, 1912), trans, and repub. in French (Paris, 1919) and German (Brunswick, 1920). With Karl Scheel he was joint general editor of Handbuch der Physik, 24 vols. (Berlin, 1926–1929) and the separately published subject index (Berlin, 1929). Geiger was also editor of vols. XXII-XXIV, dealing with the structure of matter and the nature of radiation. Geiger and Scheel extensively revised these three vols. in 1933, each of which appeared in two pts., and Geiger edited both pts. of XXII and XXIII. His own article “Durchgang von alpha Strahlen durch Materie,” in XXIV (1927), 137–190, dealing with α rediation and detection principles, was revised, expanded, and reissued in XXII, pt. 2 (1933), 155–242.

Geiger contributed “Die Radioaktivitat” to Leo Graetz, Handbuch der Elektrizitdt and des Magnetismus, III (Leipzig, 1914), 1–130. Written in 1913, the article contains an updated account of the relevant literature to the end of that year. Geiger was also instrumental in reworking the 13th and 14th eds. of Friedrich Kohlrausch, Lehrbuch der praktischen Physik (Leipzig-Berlin, 1921, 1923).

Extensive correspondence between Geiger and Rutherford from 1911 to 1937 is at Cambridge University Library, Add. MSS 7653/G.

II. Secondary Literature. Biographical material is in M. von Laue, “Nachruf,” which was included in his Gesammelte Schriften and Vortrage, III (Brunswick, 1961), 204–212; M. von Laue and R. W. Pohl, “Hans Geiger,” in Zeitschrift fur Physik, 124 (1947), 1; E. Stuhlinger, “Hans Geiger,” in Zeitschrift fur Naturforschung, 1 (1946), 50–52; and T. I. Williams, A Biographical Dictionary of Scientists (London, 1969), p. 211. Ewald Funfer, who took his doctorate under Geiger at Tubingen, contributed the article in Neue deutsche Biographie, VI (Berlin, 1964), 141–142. Some early details are in the “Lebenslauf” of Geiger’s inaugural dissertation (1906). See also Max Pollerman, in Rontgen-Blaster, 11 (1958), 33–35; and the brief account in Reichshandbuch der Deutschen Gesellschaft, I (Berlin, 1930), 528.

A brief account of Geiger’s early research is in James Chadwick, “The Rutherford Memorial Lecture, 1953,” in Proceedings of the Royal Society, 224A (1954), 441–443. Valuable background information on Geiger is in A. S. Eve, Rutherfbrd (Cambridge, 1939); and in L. Badash, ed., Rutherford and Boltwood: Letters on Radioactivity (New Haven, 1969), passim.

Physical descriptions of Geiger’s work are given in Walter Dreblow, “Das Geiger Mullersche Zahlrohr,” in Kosmos (Stuttgart), 47 (1951), 481–485; W. Christoph and W. Hanle, “Zum Mechanismus des Geiger MUllerschen Zahlrohrs,” in Physikalische Zeitschrifi, 34 (1933), 641–645; and Ewald Funfer, Zdhlrohre and Szintillationzahler, 2nd ed. (Karlsruhe, 1959), pp. 1–5, which also contains a discussion of his work.

C. Schmidt-Schonbeck, 300Jalire Physik and Astronomie an der Kieler Universitat (Kiel, 1965), pp. 136–146, focuses on Geiger’s scientific work at Kiel.

Geiger’s techniques and instrumentation are discussed in detail in W. Bothe, “Die Geigerschen Zahlmethoden: Herrn Professor Hans Geiger zu seinem 60. Geburtstage am 30 September 1942,” in Nat u rwissenschaften, 30 (1942), 593–599. The early work of Geiger is considered in A. T. Krebs, “Hans Geiger: Fiftieth Anniversary of the Publication of His Doctoral Thesis, 23 July 1906,” in Science, 124 (1956), 166.

A full treatment of Geiger’s work in its scientific context can be found in K. W. F. Kohlrausch, Radioaktivitat, vol. XV of W. Wien and F. Harms, eds., Handbuch der Experimentalphysik (Leipzig, 1928), passim. The work for which he was awarded the Hughes Medal is considered in “Hughes Medal, Awarded to Professor Hans Geiger,” in Nature, 124 (1929), 893.

An extensive bibliography containing over 300 references between 1913 and 1947 on Geiger and proportional counters was assembled by M. Healea, “Geiger and Proportional Counters,” in Nucleonics, 1 (Dec. 1947), 68–75. Additional source material is listed in T. S. Kuhn, ed., Sources for History of Quantum Physics (Philadelphia, 1967), p. 164.

Thaddeus J. Trenn