MEITNER, LISE

(b. Vienna, Austria, 7 November 1878; d. Cambridge, England, 27 October 1968)

physics.

Meitner was the third of eight children of Hedwig Skovran and Philipp Meitner, a lawyer. Although both parents were of Jewish background (and the father was a freethinker), all the children were baptized and Meitner was raised as a Protestant. Her interest in physics apparently began very early, but her parents encouraged her to study for the state examination in French, so that she could support herself as a teacher should the need arise. Meitner passed the examination, then studied privately for the test that permitted her to enter the University of Vienna in 1901. At the university she met with some rudeness from her fellows (a female student then being something of a freak) but was inspired by her teachers, particularly Boltzmann. She was the second woman to receive a doctorate in science from the university; her dissertation, in 1905, was on heat conduction in nonhomogeneous materials.

After graduation Meitner remained in Vienna for a time, during which she was introduced to the new subject of radioactivity by Stephan Meyer. Although she then had no notion of making the study of radioactivity her life’s work, she did design and perform one of the first experiments to demonstrate that alpha rays are slightly deflected in passing through matter. But she was also interested in theoretical physics; she requested and obtained her father’s (very modest) financial support to go to Berlin to study with Planck— for a year or two, as she thought.

Meitner enrolled for Planck’s lectures, but had some difficulty finding a place to do experimental work until she met Otto Hahn, who was looking for a physicist to help him in his work on the chemistry of radioactivity. Hahn himself was working at the Chemical Institute, under Emil Fischer, who did not allow women in his laboratory (although two years later, after women’s education had been regularized in Berlin, he welcomed Meitner). Hahn and Meitner equipped a carpenter’s workshop for radiation measurement and set to work. Hahn, the chemist, was primarily interested in the discovery of new elements and the examination of their properties, while Meitner was more concerned with disentangling their radiations. They were pioneers, and a great deal of their first work was based on false assumptions—such as H. W, Schmidt’s idea that beta rays of defined energy follow an exponential absorption law —so that most of their early papers are of largely historical interest.

In 1912 Meitner joined the Kaiser-Wilhelm Institut für Chemie, newly opened in Berlin-Dahlem. World War I interrupted her work; Hahn was called to military service, and Meitner volunteered as a roentgenographic nurse with the Austrian army. On her leaves she went back to Berlin to measure radioactive substances; Hahn’s leaves sometimes coincided with hers, so that they could occasionally continue their collaboration. Since in the study of radioactive substances measurements made at fairly long intervals may be desirable to allow some activities to build up and others decay, Hahn and Meitner were able to make a virtue of necessity. By this time they were searching for the still unknown precursor of actinium; they reported their success at the end of the war, naming the new element protactinium.

In 1918 Meitner was appointed head of the physics department of the Kaiser-Wilhelm Institut. She also maintained her rather tenuous connection with the University of Berlin —from 1912 to 1915 she had been Planck’s assistant, and after the war she became a docent. Her inaugural lecture was given in 1922; it concerned cosmic physics (reported in the press as “cosmetic physics”). Meitner was appointed extraordinary professor in 1926; she never gave any courses, although she did contribute to the weekly physics colloquia, in which her colleagues included Planck, Einstein, Nernst, Gustav Hertz, and Schroedinger.

Meitner continued her work toward clarifying the relationships between beta and gamma rays. It had by then become clear that while some radioactive substances emitted an electron from the nucleus, others did not. The electrons that these latter substances, the alpha emitters, released must therefore come from the outer shell (as was presumably the case for some of those issued by the true electron emitters), and must therefore be regarded as secondary. There remained the determination of which of the many electron lines then identified were primary electrons from the nucleus. Ellis, at Cambridge, thought that none of them were, but rather that the primary electrons constituted the continuous spectrum that Chadwick had discovered as early as 1914. Meitner disagreed, in the belief that Chadwick’s method was inadequate for the discrimination of such a spectrum. Chadwick had counted electrons deflected by a fixed angle in a variable magnetic field; Meitner had always put her faith in photographing electrons. In 1922 she published the measurements that she had made using Danysz’ method of focusing the electrons by deflection through 180°. This technique emphasized the narrow electron lines, while the continuous spectrum appeared to be very faint, and Meitner attributed the latter to secondary effects.

Meitner’s skepticism was, moreover, a product of her belief that, like alpha particles, primary electrons must form a group of well-defined energy. Her conviction was in the spirit of the quantum theory, which was then being applied to nuclei (largely by Gamow).

If the primary electrons display a continuous spectrum it must be, she thought, because they lose varying amounts of energy in the form of X rays on passing through the strong electric field that surrounds the nucleus, or perhaps in collisions with atomic electrons. The primary energy would then correspond to the highest energy found in the continuous spectrum. In 1927, however, Ellis and Wooster measured the heat generated by electron-emitting nuclei and thus found that each electron gives to its surrounding material an energy equal to the mean energy of the continuous spectrum, not its top energy as Meitner’s view demanded. With Wilhelm Orthmann, Meitner immediately set out to check Ellis and Wooster’s result; she reported good agreement with their data in the paper that she and Orthmann published jointly in 1929.

The growing evidence for the continuous distribution of energy of primary electrons emitted in beta decay led Pauli to write to Meitner and Geiger a letter in which he proposed the existence of a new neutral particle—later called the neutrino—that should be emitted together with the electron and would at random share the energy available to it. Pauli had to assume that this particle was too elusive to be detected by means then available, and, indeed, effects due to free neutrinos were not actually found until 1956.

Although Meitner’s belief in the simplicity of nature had led her astray in regard to the distribution of energy of primary electrons, she was correct in her theory that electron lines were generated from the outer electron shell. She measured the electron lines of actinium to demonstrate that they were produced from the shells of the newly formed—rather than the decaying—nucleus. She thus showed that gamma rays follow upon radioactive transformation, rather than acting as the triggering mechanism for it (as Ellis had suggested). She further observed and correctly interpreted those radiationless transitions in which an electron, on dropping into a vacancy in an inner shell, ejects another electron from the atom, a phenomenon usually named for Auger, who independently described it about two years later in a different context.

Although Meitner never invented a laboratory instrument or technique of her own, she rapidly adopted any new methods developed by others that seemed to her to be useful in her work. For example, she encouraged her student Gerhard Schmidt to make use of Millikai’ droplet technique to study the ionization density of alpha particles, and introduced C. T. R. Wilson’s cloud chamber—which had been neglected since its invention in 1911—into her Berlin laboratory and applied it in innovative researches (as, for instance, the study of slow electrons, for which she employed the device at greatly lowered pressure). Among her own investigations, she was one of the first (with Phillip, in a paper dated March 1933) to observe and report on positrons formed from gamma rays.

Meitner had accurately measured the attenuation of hard gamma rays in their passage through matter even earlier, when she realized the potential of the new Geiger-Mueller counter for measuring the attenuation of well-collinated, narrow beams of gamma rays. The main purpose of that measurement was to test the Klein-Nishina formula for the Compton effect, and she found good agreement for light elements, up to magnesium. She discovered, however, that attenuation increased with atomic number; she suspected an effect of nuclear structure, perhaps a resonance, and therefore searched for the scattering of gamma rays with unchanged wavelength. (In 1933 it was discovered that the excess attenuation was due to the formation of electron-positron pairs, rather than to scattering.)

In the early 1930’s nuclear physics advanced dramatically: the neutron was discovered in 1932, the positron in 1933, and artificial radioactivity in 1934. Meitner and her colleagues published a number of short papers in the light of these rapid developments. In 1934 Meitner resumed work with Hahn to follow up results obtained by Fermi, who had bombarded uranium with neutrons and had found several radioactive products which he thought must be due to a transuranic element since neutron bombardment had invariably led to the formation of a heavier, usually beta-radioactive, isotope of the bombarded element (except for the lightest elements, where a nucleus of lower atomic number might result from the ejection of a charged particle such as a proton or a helium nucleus).

In his investigation of this phenomenon, Hahn discovered several decay products for uranium, some of which might be presumed to be transuranic, with atomic numbers greater than 92. He and Meitner set out to isolate such elements by precipitating an irradiated and acidified uranium salt solution with hydrogen sulfide in order to eliminate all elements between polonium (84) and uranium (92); they assumed that the remaining precipitate must contain only transuranic elements. To be sure, Ida Noddack had suggested that the formation of transuranic elements could not be regarded as proven until it could be established that such elements were not, in fact, identical with any elements between hydrogen and uranium, but her paper was little read and uninfluential. Meitner and Hahn were thus considerably surprised when Irene Curie and Savitch reported irradiating uranium to find a product with penetrating beta rays and a half-life of three-and-one-half hours. Curie further noted that this substance behaved chemically somewhat like thorium. (Hahn and Meitner, using sulfide precipitation, would have misled that.) By implication, then, a uranium nucleus upon being hit by a neutron might emit an alpha particle—a helium nucleus—which seemed unlikely. Later Curie changed her view and pointed to the similarity of her three-and-one-half-hour substance with lanthanum, foreshadowing, but not formulating, the concept of nuclear fission.

Meitner set one of her students, Gottfried von Droste, to look for such alpha particles, but he failed to find them. By studying substances not precipitated as sulfide, Hahn and Strassmann found yet more products, with actinium-like properties and, startlingly, three others with the properties of radium, four places below uranium on the atomic scale.

These results puzzled Meitner, who was unable to reconcile them with nuclear theory. It was at this point, however, that she was forced to interrupt her researchse and leave Germany, where the Nazi racial laws had made it increasingly difficult for her to work. Although the Kaiser-Wilhelm Inslitut was to some degree autonomous, Nazi policies were being enforced even there, and Meitner’s situation became critical when the occupation of Austria robbed her of the protection of her foreign nationality. She had never concealed her Jewish origin; her Austrian passport was invalid, and her dismissal from the institute certain. The Dutch physicist Peter Debye communicated (through Scherrer in Zürich) with Dirk Coster at the University of Groningen, and Coster arranged that Meitner be allowed to enter Holland, despite her lack of papers. No one except Hahn knew that she was leaving Germany for good.

Meitner remained in Holland for only a short time, then went to Denmark, where she was the guest of Niels Bohr and his wife. Although Copenhagen offered her good facilities for research, and although there were a number of younger nuclear physicists working there (including her nephew, O. R. Frisch), Meitner soon chose to accept an invitation from Manne Siegbahn to work in the new Nobel Institute in Stockholm, where a cyclotron was being constructed. Meitner was sixty years old when she went to Sweden; she nonetheless acquired a good command of the language, built up a small research group, and eventually published a number of short papers, most of them on the properties of new radioactive species formed with the cyclotron.

Meitner made her most famous contribution to science shortly after she arrived in Stockholm, however. Worried by Hahn’s statement that neutron bombardment of uranium leads to isotopes of radium, she had written to Hahn to ask for irrefutable data concerning the properties of these substances. Her request led Hahn and Strassmann to undertake a series of tests designed to demonstrate that these products were chemically identical to radium, as their earlier investigations had suggested. Hahn wrote to inform her that in these tests, he and Strassmann had found that, like radium, these substances could be precipitated with barium but, surprisingly, were then inseparable from it. They therefore reluctantly concluded that the decay products were isotopes of barium, rather than radium. The evidence for transuranic elements was thus placed in doubt, since sulfide precipitation did not eliminate elements lighter than polonium.

Meitner discussed this news with Frisch. It soon became clear that Bohr’s droplet model of the nucleus must provide the clue to understanding how barium nuclei could be formed from uranium nuclei, which are almost twice as heavy. Frisch suggested that the division into two smaller nuclei was made possible through the mutual repulsion of the many protons of the uranium nucleus, making it behave like a droplet in which the surface tension has been greatly reduced by its electric charge. Meitner estimated the difference between the mass of the uranium nucleus (plus the extra neutron with which it had been bombarded) and the slightly smaller total mass of the two fragment nuclei; from this she worked out (by Einstein’s massenergy equivalence) the large amount of energy that was bound to be released. The two mutually repulsed fragments would, indeed, be driven apart with an energy that agreed with her value, so it all fitted.

Meitner and Frisch reported these findings in a joint paper that described this “nuclear fission” (composed over the telephone, since she was in Stockholm and he had returned to Copenhagen). A few months later they jointly demonstrated experimentally that radioactive fission fragments could be collected on a water surface close to a uranium layer undergoing neutron irradiation. They further showed that the sulfide precipitated from the material so obtained had a decay curve of the same shape as the precipitate derived directly from the irradiated uranium. They concluded that no observable amounts of transuranic elements were produced, capable of affecting their counters.

Meitner had, however, previously demonstrated that one of the products of slow-neutron irradiation of uranium was a uranium isotope of twenty-four minutes half-life; by measuring the resonance cross section she concluded that it was U-239, formed by the capture of a neutron in U-238. Although she realized that its observed beta decay must lead to the formation of a transuranic element, she was not able to observe the very soft radiation of that daughter substance. (Macmillan later found this substance, neptunium; the next generation, plutonium, was the exptosive of the first atomic bomb.) Meitner was invited to join the team at work on the development of the nuclear-fission bomb; she refused, and hoped until the very end that the project would prove impossible. Except for a brief note on the asymmetry of fission fragments, she did no more work in nuclear fission.

In 1946 Meitner spent half a year in Washington, D. C., as a visiting professor at Catholic University. In 1947 she retired from the Nobel Institute and went to work in the small laboratory that the Swedish Atomic Energy Commission had established for her at the Royal Institute of Technology. She later moved to the laboratory of the Royal Academy for Engineering Sciences, where an experimental nuclear reactor was being built. In 1960, having spent twenty-two years in Sweden. Meitner retired to Cambridge (England). She continued to travel, lecture, and attend concerts (her love of music was lifelong), but she gradually gave up these activities as her strength ebbed. She died a few days before her ninetieth birthday.

BIBLIOGRAPHY

Meitner’s earlier writings include “Über die Zerstreuung der α-Strahlen,” in Berichte der Deutsche physikalisehen Gesellschaft. 8 (1907), 489; “Eine neue Methode zur Herstellung radioaktiver Zerfallsprodukte; Thorium D, ein kurzlebiges Produkt des Thoriums,” in Verhandlungen der Deutschen physikalischen Gesellschaft. 11 (1909), 55, written with O. Hahn; “Vorträge aus dem Gebiet der Radioaktivität,” in Physikalische Zeitschrift, 12 (1911), 147; “Magnetische Spektren der β-Strahlen des Radiums,” ibid., 1099, written with O. von Baeyer and O. Hahn; “Die Muttersubstanz des Actiniums, ein neues radioaktives Element von langer Lebensdauer,” ibid., 19 (1918), 208, written with O. Hahn; “Über die verschiedenen Arten des radioaktiven Zerfalls und die Möglichkeit ihrer Deutung aus der Kernstruktur,” in Zeitschrift für Physik, 4 (1921), 146; “Die γ-Strahlung der Actiniumreihe und der Nachweis, dass die γ-Strahlen erst nach erfolgtem Atomzerfall emittiert werden,” ibid., 34 (1925), 807” Einige Bemerkungen zur Isotopie der Elemente,” in Naturwissenschaften, 14 (1926), 719; Experimentelle Bestimmung der Reichweite homogener β-Slrahlen,” ibid., 1199; “Über eine absolute Bestimmung der Energie der primären β-Strahlen von Radium E,” in Zeitschrift für Physik, 60 (1930), 143, written with W. Orthmann; and “Über das Absorptionsgesetz für kurzwellige γ-Strahlung,” ibid., 67 (1931), 147, written with H. H. Hupfeld.

Later works are “Die Anregung positiver Elektronen durch γ-Strahlen von Th C,” in Naturwissenschaften, 21 (1933), 468, written with K. Philipp; Kernphysikalische Vorträge am Physikalischen Institut der Eidgenössischen technischen Hochschule (Berlin, 1936); “über die Umwandlungsreihen des Urans, die durch Neutronenbestrahlung erzeugt werden,” in Zeitschrift für Physik, 106 (1937), 249, written with O. Hahn and F. Strassmann; “Künstliche Umwandlungsprozesse bei Bestrahlung des Thoriums mit Neutronen; Auftreten isomerer Reihen durch Abspaltung von à-Strahlen,” ibid., 109 (1938), 538, written with O. Hahn and F. Strassmann; “Trans-Urane als künstliche radioaktive Umwandlungsprodukte des Urans,” in Scientia (Jan. 1938), written with O. Hahn; “Disintegration of Uranium by Neutrons; a New Type of Nuclear Reaction,” in Nature, 143 (1939), 239, written with O. R. Frisch; “Resonance Energy of the Th Capture Process,” in Physical Review, 60 (1941), 58; “Spaltung und Schalen modell des Atomkernes,” in Arkiv för fysik, 4 (1950), 383—see Nature, 165 (1950), 561; “Die Anwendung des Rückstosses bei Atomkernprozessen,” in Zeitschrift für Physik, 133 (1952), 141; “Einige Erinnerungen an das Kaiser-Wilhelm-Institut für Chemie in Berlin-Dahlem,” in Naturwissenschaften, 41 (1954), 97; and “Looking Back,” in Bulletin of the Atomic Scientists (Nov, 1964), 2.

A biography with extensive bibliography is by O. R. Frisch, in Biographical Memoirs of Fellows of the Royal Society, 16 (Nov. 1970), 405–420.

O. R. Frisch

Lise Meitner

Lise Meitner (1878-1968) helped to develop the theory behind nuclear fission, and became the first woman professor in Germany.

The prototypical female scientist of the early twentieth century was a woman devoted to her work, sacrificing family and personal relationships in favor of science; modestly brilliant; generous; and underrecognized. In many ways Austrian-born physicist Lise Meitner embodies that image. In 1938, along with her nephew Otto Robert Frisch, Meitner developed the theory behind nuclear fission that would eventually make possible the creation of the atomic bomb. She and lifelong collaborator Otto Hahn made several other key contributions to the field of nuclear physics. Although Hahn received the Nobel Prize in 1944, Meitner did not share the honor—one of the more frequently cited examples of the sexism rife in the scientific community in the first half of this century.

Elise Meitner was born November 7, 1878 to an affluent Vienna family. Her father Philipp was a lawyer and her mother Hedwig travelled in the same Vienna intellectual circles as Sigmund Freud. From the early years of her life, Meitner gained experience that would later be invaluable in combatting—or overlooking—the slights she received as a woman in a field dominated by men. The third of eight children, she expressed interest in pursuing a scientific career, but her practical father made her attend the Elevated High School for Girls in Vienna to earn a diploma that would enable her to teach French—a much more sensible career for a woman. After completing this program, Meitner's desire to become a scientist was greater than ever. In 1899, she began studying with a local tutor who prepped students for the difficult university entrance exam. She worked so hard that she successfully prepared for the test in two years rather than the average four. Shortly before she turned twenty three, Meitner became one of the few women students at the University of Vienna.

At the beginning of her university career in 1901, Meitner could not decide between physics or mathematics; later, inspired by her physics teacher Ludwig Boltzmann, she opted for the latter. In 1906, after becoming the second woman ever to earn a Ph.D. in physics from the University of Vienna, she decided to stay on in Boltzmann's laboratory as an assistant to his assistant. This was hardly a typical career path for a recent doctorate, but Meitner had no other offers, as universities at the time did not hire women faculty. Less than a year after Meitner entered the professor's lab, Boltzmann committed suicide, leaving the future of the research team uncertain. In an effort to recruit the noted physicist Max Planck to take Boltzmann's place, the university invited him to come visit the lab. Although Planck refused the offer, he met Meitner during the visit and talked with her about quantum physics and radiation research. Inspired by this conversation, Meitner left Vienna in the winter of 1907 to go to the Institute for Experimental Physics in Berlin to study with Planck.

Soon after her arrival in Berlin, Meitner met a young chemist named Otto Hahn at one of the weekly symposia. Hahn worked at Berlin's Chemical Institute under the supervision of Emil Fischer, surrounded by organic chemists—none of whom shared his research interests in radiochemistry. Four months older than Hahn, Meitner was not only intrigued by the same research problems but had the training in physics that Hahn lacked. Unfortunately, Hahn's supervisor balked at the idea of allowing a woman researcher to enter the all-male Chemical Institute. Finally, Fischer allowed Meitner and Hahn to set up a laboratory in a converted woodworking shop in the Institute's basement, as long as Meitner agreed never to enter the higher floors of the building.

This incident was neither the first nor the last experience of sexism that Meitner encountered in her career. According to one famous anecdote, she was solicited to write an article by an encyclopedia editor who had read an article she wrote on the physical aspects of radioactivity. When she answered the letter addressed to Herr Meitner and explained she was a woman, the editor wrote back to retract his request, saying he would never publish the work of a woman. Even in her collaboration with Hahn, Meitner at times conformed to gender roles. When British physicist Sir Ernest Rutherford visited their Berlin laboratory on his way back from the Nobel ceremonies in 1908, Meitner spent the day shopping with his wife Mary while the two men talked about their work.

Within her first year at the Institute, the school opened its classes to women, and Meitner was allowed to roam the building. For the most part, however, the early days of the collaboration between Hahn and Meitner were filled with their investigations into the behavior of beta rays as they passed through aluminum. By today's standards, the laboratory in which they worked would be appalling. Hahn and Meitner frequently suffered from headaches brought on by their adverse working conditions. In 1912 when the Kaiser-Wilhelm Institute was built in the nearby suburb of Dahlem, Hahn received an appointment in the small radioactivity department there and invited Meitner to join him in his laboratory. Soon thereafter, Planck asked Meitner to lecture as an assistant professor at the Institute for Theoretical Physics. The first woman in Germany to hold such a position, Meitner drew several members of the news media to her opening lecture.

When World War I started in 1914, Meitner interrupted her laboratory work to volunteer as an X-ray technician in the Austrian army. Hahn entered the German military. The two scientists arranged their leaves to coincide and throughout the war returned periodically to Dahlem where they continued trying to discover the precursor of the element actinium. By the end of the war, they announced that they had found this elusive element and named it protactinium, the missing link on the periodic table between thorium (previously number 90) and uranium (number 91). A few years later Meitner received the Leibniz Medal from the Berlin Academic of Science and the Leibniz Prize from the Austrian Academy of Science for this work. Shortly after she helped discover protactinium in 1917, Meitner accepted the job of establishing a radioactive physics department at the Kaiser Wilhelm Institute. Hahn remained in the chemistry department, and the two ceased working together to concentrate on research more suited to their individual training. For Meitner, this constituted a return to beta radiation studies.

Throughout the 1920s, Meitner continued her work in beta radiation, winning several prizes. In 1928, the Association to Aid Women in Science upgraded its Ellen Richards Prize—billing it as a Nobel Prize for women—and named Meitner and chemist Pauline Ramart-Lucas of the University of Paris its first recipients. In addition to the awards she received, Meitner acquired a reputation in physics circles for some of her personal quirks as well. Years later, her nephew Otto Frisch, also a physicist, would recall that she drank large quantities of strong coffee, embarked on ten mile walks whenever she had free time, and would sometimes indulge in piano duets with him. By middle age, Meitner had also adopted some of the mannerisms stereotypically associated with her male colleagues. Not the least of these, Hahn later recalled, was absent-mindedness. On one occasion, a student approached her at a lecture, saying they had met earlier. Knowing she had never met the student, Meitner responded earnestly, "You probably mistake me for Professor Hahn."

Meitner and Hahn resumed their collaboration in 1934, after Enrico Fermi published his seminal article on "transuranic" uranium. The Italian physicist announced that when he bombarded uranium with neutrons, he produced two new elements—number 93 and 94, in a mixture of lighter elements. Meitner and Hahn joined with a young German chemist named Fritz Strassmann to draw up a list of all the substances the heaviest natural elements produced when bombarded with neutrons. In three years, the three confirmed Fermi's result and expanded the list to include about ten additional substances that resulted from bombarding these elements with neutrons. Meanwhile, physicists Irène Joliot-Curie and Pavle Savitch announced that they had created a new radioactive substance by bombarding uranium by neutrons. The French team speculated that this new mysterious substance might be thorium, but Meitner, Hahn, and Strassmann could not confirm this finding. No matter how many times they bombarded uranium with neutrons, no thorium resulted. Hahn and Meitner sent a private letter to the French physicists suggesting that perhaps they had erred. Although Joliot-Curie did not reply directly, a few months later she published a paper retracting her earlier assertions and said the substance she had noted was not thorium.

Current events soon took Meitner's mind off these professional squabbles. Although her father, a proponent of cultural assimilation, had all his children baptized, Meitner was Jewish by birth. Because she continued to maintain her Austrian citizenship, she was at first relatively impervious to the political turmoil in Weimar Germany. In the mid-1930s she had been asked to stop lecturing at the university but she continued her research. When Germany annexed Austria in 1938, Meitner became a German citizen and began to look for a research position in an environment hospitable to Jews. Her tentative plans grew urgent in the spring of 1938, when Germany announced that academics could no longer leave the country. Colleagues devised an elaborate scheme to smuggle her out of Germany to Stockholm where she had made temporary arrangements to work at the Institute of the Academy of Sciences under the sponsorship of a Nobel grant. By late fall, however, Meitner's position in Sweden looked dubious: her grant provided no money for equipment and assistance, and the administration at the Stockholm Institute would offer her no help. Christmas found her depressed and vacationing in a town in the west of Sweden.

Back in Germany, Hahn and Strassmann had not let their colleague's departure slow their research efforts. The two read and reread the paper Joliot-Curie had published detailing her research techniques. Looking it over, they thought they had found an explanation for Joliot-Curie's confusion: perhaps instead of finding one new substance after bombarding uranium, as she had thought, she had actually found two new substances! They repeated her experiments and indeed found two substances in the final mixture, one of which was barium. This result seemed to suggest that bombarding uranium with neutrons led it to split up into a number of smaller elements. Hahn immediately wrote to Meitner to share this perplexing development with her. Meitner received his letter on her vacation in the village of Kungalv, as she awaited the arrival of her nephew, Frisch, who was currently working in Copenhagen under the direction of physicist Niels Bohr. Frisch hoped to discuss a problem in his own work with Meitner, but it was clear soon after they met that the only thing on her mind was Hahn and Strassmann's observation. Meitner and Frisch set off for a walk in the snowy woods—Frisch on skis, with his aunt trotting along—continuing to puzzle out how uranium could possibly yield barium. When they paused for a rest on a log, Meitner began to posit a theory, sketching diagrams in the snow.

If, as Bohr had previously suggested, the nucleus behaved like a liquid drop, Meitner reasoned that when this drop of a nucleus was bombarded by neutrons, it might elongate and divide itself into two smaller droplets. The forces of electrical repulsion would act to prevent it from maintaining its circular shape by forming the nucleus into a dumbbell shape that would—as the bombarding forces grew stronger—sever at the middle to yield two droplets—two completely different nuclei. But one problem still remained. When Meitner added together the weights of the resultant products, she found that the sum did not equal the weight of the original uranium. The only place the missing mass could be lost was in energy expended during the reaction.

Frisch rushed back to Copenhagen, eager to test the revelations from their walk in the woods on his mentor and boss, Bohr. He caught Bohr just as the scientist was leaving for an American tour, but as Bohr listened to what Frisch was urgently telling him, he responded: "Oh, what idiots we have been. We could have foreseen it all! This is just as it must be!" Buoyed by Bohr's obvious admiration, Frisch and Meitner spent hours on a long-distance telephone writing the paper that would publicize their theory. At the suggestion of a biologist friend, Frisch coined the word "fission" to describe the splitting of the nucleus in a process that seemed to him analogous to cell division.

The paper "On the Products of the Fission of Uranium and Thorium" appeared in Nature on February 11, 1939. Although it would be another five and a half years before the American military would successfully explode an atom bomb over Hiroshima, many physicists consider Meitner and Frisch's paper akin to opening a Pandora's box of atomic weapons. Physicists were not the only ones to view Meitner as an important participant in the harnessing of nuclear energy. After the bomb was dropped in 1944, a radio station asked First Lady Eleanor Roosevelt to conduct a transatlantic interview with Meitner. In this interview, the two women talked extensively about the implications and future of nuclear energy. After the war, Hahn found himself in one of the more enviable positions for a scientist—the winner of the 1944 Nobel prize in chemistry—although, because of the war, Hahn did not accept his prize until two years later. Although she attended the ceremony, Meitner did not share in the honor.

But Meitner's life after the war was not without its plaudits and pleasures. In the early part of 1946, she travelled to America to visit her sister—working in the U.S. as a chemist—for the first time in decades. While there, Meitner delivered a lecture series at Catholic University in Washington, D.C. In the following years, she won the Max Planck Medal and was awarded numerous honorary degrees from both American and European universities. In 1966 she, Hahn, and Strassmann split the $50,000 Enrico Fermi Award given by the Atomic Energy Commission. Unfortunately, by this time Meitner had become too ill to travel, so the chairman of the A. E. C. delivered it to her in Cambridge, England, where she had retired a few years earlier. Meitner died just a few weeks before her 90th birthday on October 27, 1968.

Further Reading

Crawford, Deborah, Lise Meitner, Atomic Pioneer, Crown, 1969.

Irving, David, The German Atomic Bomb: The History of Nuclear Research in Nazi Germany, Simon & Schuster, 1967.

Rhodes, Richard, The Making of the Atom Bomb, Simon & Schuster, 1988.

Watkins, Sallie, "Lise Meitner and the Beta-ray Energy Controversy: An Historical Perspective," in American Journal of Physics, Volume 51, 1983, pp. 551-553.

Watkins, Sallie, "Lise Meitner: The Making of a Physicist," in Physics Teacher, January, 1984, pp. 12-15. □

Meitner, Lise

AUSTRIAN PHYSICIST
1878–1968

On any list of scientists who should have won a Nobel Prize but did not, Lise Meitner's name would be near the top. She was the physicist who first realized that the atomic nucleus could be split to form pairs of other atomic nuclei—the process of nuclear fission . Although she received many honors for her work, the greatest of all was to elude her because of the unprofessional conduct of her colleague Otto Hahn.

Born in Vienna, Meitner decided early on that she had a passion for physics. At that time, education for female children in the Austro-Hungarian Empire terminated at fourteen, as it was argued that girls did not need any more education than that to become a proper wife and mother. Willing to support his daughter's aspirations, her father paid for private tutoring so she could cover in two years the eight years of education normally needed for university entrance. In 1901 Meitner was one of only four women admitted to the University of Vienna, and in 1905 she graduated with a Ph.D. in physics.

As a student, Meitner had become fascinated with the new science of radioactivity, but she realized that she would have to travel to a foreign country to pursue her dream of working in this field. She applied for work with Marie Curie, but was rejected. However, she did eventually receive an offer from the University of Berlin, which had just hired a young scientist by

the name of Otto Hahn. Having a chemical background, Hahn was looking for a collaborator with a theoretical physics background. Unfortunately, the chemistry institute at the university was run by Emil Fischer who had banned women from the institute's premises. Reluctantly, Fischer agreed to let Meitner work in a small basement room. During this time, she received no salary and relied on her family for enough money to cover her living expenses. Meitner and Hahn's research during this time period resulted in the discovery of the element protactinium.

The post–World War I government in Germany was much more favorable to women, and Meitner became the first woman to serve as a physics professor in that country. By the 1930s scientists were bombarding heavy elements with neutrons and it was claimed that new superheavy elements formed as a result of this process. Using such a procedure, Meitner and Hahn thought they had discovered nine new elements. Meitner was puzzled by all the new elements for which claims were made.

Unfortunately, the Nazi Party's rise to power changed everything for Meitner. Because she was a Jew by birth, although a later convert to Christianity, Meitner's situation became increasingly precarious. With help from a Dutch scientist, Dirk Coster, she escaped across the German border into Holland and then made her way to Stockholm, where the director of the Nobel Institute for Experimental Physics reluctantly offered her a position. Stockholm had one advantage for Meitner, an overnight mail service to Germany so she could keep in regular contact with Hahn.

On December 19, 1938, Hahn sent Meitner a letter describing how one of the new elements had chemical properties strongly resembling those of barium and asking if she could provide an explanation. The physicist Otto Frisch visited Meitner, his aunt, for Christmas to help dispel her loneliness. While there, the two went for the now famous "walk in the snow." During an extended conversation in the woods, they came to realize that if the nucleus was considered a liquid drop, the impact of a subatomic particle could cause the atom to fission. If so, it was possible that the barium-like element was actually barium itself.

Meitner immediately contacted Hahn and his colleague Fritz Strassmann. Through experiment they confirmed that the so-called new element was indeed barium. They reported their discovery of nuclear fission to the world's scientific press, barely mentioning the names of Meitner and Frisch. In fact, Hahn never admitted that it was Meitner who had made the critical conceptual breakthrough. In 1944 Hahn was awarded the Nobel Prize in chemistry for his contribution to the discovery of nuclear fission.

Although nominated several times, Meitner never did receive the Nobel Prize for physics that many scientists considered her due. Only now, with element 109 having been named Meitnerium (symbol Mt) has she finally received some recognition for her crucial work. Meitner retired to England where she died at the age of eighty-nine.

see also Barium; Curie, Marie Sklodowska; Fischer, Emil Hermann; Nuclear Fission; Protactinium; Radiation.

Marelene Rayner-Canham

Geoffrey W. Rayner-Canham

Bibliography

McGrayne, Sharon Bertsch (1993). Nobel Prize Women in Science: Their Lives, Struggles and Momentous Discoveries. New York: Birch Lane Press.

Rayner-Canham, Marelene, and Rayner-Canham, Geoffrey (1998). Women in Chemistry: Their Changing Roles from Alchemical Times to the Mid-Twentieth Century. Washington, DC: American Chemical Society and the Chemical Heritage Foundation.

Sime, Ruth Lewin (1996). Lise Meitner: A Life in Physics. Berkeley: University of California Press.

Internet Resources

"Lise Meitner Online." Available from <http://www.users.bigpond.com/Sinclair/fission/LiseMeitner.html>.

Lise Meitner

1878-1968

Austrian-Swedish Physicist and Radiochemist

Lise Meitner is best known for her role in the discovery that heavy unstable nuclei such as uranium-235 could decay by a fission process in which the nucleus could split into two pieces of nearly equal size, releasing additional neutrons and an immense amount of energy. When physicists realized that the neutrons could be used to initiate additional fission events, it became apparent that a chain reaction could realized, leading eventually to the first atomic bombs.

Lisa Meitner entered the University of Vienna in 1901. Although she was encouraged by a number of the physics faculty, including the eminent Ludwig Boltzmann (1844-1906), she received a rather unfriendly reception from the largely male student body. In 1905 she became the second woman to receive a doctorate from the University. Following graduation she moved to Berlin where she planned to study under Max Planck (1858-1947). There she began a lasting collaboration with Otto Hahn (1879-1968), a chemist interested in discovering new elements. As a physicist, Meitner was interested in understanding the alpha, beta, and gamma rays that made the creation of the new elements possible. In 1912 Meitner joined the newly established Kaiser Wilhelm Institute in Berlin, and in 1918 she was made head of its physics department. In 1926 she received a professorial appointment at the University of Berlin, but did not teach any courses.

In 1898 Marie Curie (1867-1934), assisted by her husband Pierre (1859-1906), had announced the discovery of two previously unknown elements, polonium and radium, products of the radioactive decay of uranium. In 1919, the English physicist Ernest Rutherford (1871-1937) discovered that the bombardment of nitrogen atoms by alpha particles resulted in the transmutation of some of them into oxygen atoms. Interest in atomic transmutations increased dramatically following the discovery of the neutron by Sir James Chadwick (1891-1974) in 1932. Since the neutron, unlike the alpha particle, had no charge, it could penetrate the nucleus readily. By 1934 Meitner and Hahn were trying to understand the result of experiments in which Italian physicist Enrico Fermi (1901-1954) had bombarded uranium with neutrons. In particular, they were looking for socalled transuranic element, elements heavier than uranium.

It was during the research on uranium that Meitner was forced to leave Germany. Of Jewish ancestry, but initially protected from the Nazi racial policies by her Austrian citizenship, her situation changed abruptly when Germany annexed Austria. Colleagues arranged safe passage for her to the Netherlands, and from there she accepted an invitation to work at the new Nobel Institute in Stockholm. Continuing the research on uranium, Hahn and Fritz Strassman (1902-1980) concluded that the neutron bombardment produced isotopes of radium, because they shared the same chemical properties as barium, as had the radium isolated by the Curies. Meitner doubted this result and asked Hahn and Strassman to prove that they had in fact produced radium. When the chemical tests were run, they found that the radioactive products could not be separated from barium at all. After discussing the new results with her nephew, Otto Frisch (1904-1979), also a physicist, Meitner came to the conclusion that what had occurred was the fission, or splitting, of the uranium nucleus into two nearly equal fragments, one of them a barium isotope, with the release of additional neutrons. Meitner calculated the energy released by the process, which was quite large, and communicated the results to Hahn.

Hahn and Strassman mentioned Meitner's work in their 1939 publication on nuclear fission, but perhaps for political reasons, they understated her contribution. As physicists learned of nuclear fission, many began to think of the possibility of a nuclear explosive, leading in the United States to the Manhattan Project and the explosion of atomic bombs over Japan in 1945. Meitner had been invited to join the project, but unlike the vast majority of refugee scientists, she refused, strongly objecting to the military use of her work. Meitner continued to work in physics and to oppose the military use of atomic energy until nearly the end of her very long and productive life.

DONALD R. FRANCESCHETTI

MEITNER, LISE

MEITNER, LISE (1878–1968), physicist and one of the small group responsible for the discovery of atomic fission. Born in Vienna, she moved to Berlin in 1917 and there joined the distinguished chemist Otto Hahn, with whom she worked in collaboration, researching into radioactive substances. Lise Meitner was one of the first women to become a professor at the University of Berlin (1926). From 1917 she was for over 20 years head of the physics department in the Kaiser Wilhelm Institute for chemistry in Berlin.

After the Anschluss in 1938, she left Germany and settled in Stockholm, working on the staff of the Nobel Institute. There she received a letter from Hahn describing his discovery with Fritz Strassmann that, when a uranium atom was disintegrated by a neutron, an atom of barium was thereby produced. While holidaying near Gothenburg in December 1938, she discussed this with her nephew, Otto *Frisch, who was working in Denmark with Niels *Bohr. The two physicists immediately realized the significance of Hahn's work, which meant that the uranium atom was split into roughly equal parts, accompanied by a tremendous release of energy. Frisch called this "fission," a term borrowed from biology. Lise Meitner visited the United States after 1945, but returned to Sweden and became a citizen in 1949. Both before and after World War ii she received many honors. She eventually retired to Cambridge, England, where she died.

bibliography:

New York Times (Oct. 28, 1968); E. Yost, in: Science Digest (May 1962), 83–88.

[Maurice Goldsmith]