Lise Meitner (1878-1968): Pioneer of nuclear fission
By Professer Gerald Lander
Institute for Transuranium Elements, Karlsruhe, Germany
& Institut Laue Langevin, Grenoble, France
Lise Meitner was born on the 7th November 1878 in Leopoldstadt, Vienna, Austria, and she was the third of eight children. Her father, Philipp Meitner, was one of the first Jewish lawyers in Austria. Her mother Hedwig travelled in the same Vienna intellectual circles as Sigmund Freud.
Lise’s favourite subjects at school were mathematics and science, particularly physics and she was very good at them but by the time she was 14 she had completed as much education as a girl at this time could possibly achieve. Further education wasn’t deemed necessary because women didn’t attend University.
Lise wanted to continue to learn and her parents’ were very supportive of her desire to attend the University of Vienna but they encouraged her to study for the state examination in French, so that she could support herself as a French teacher should the need arise. Meitner passed the examination, and then in 1899 studied privately for the “externe Matura” examination at the Akademisches Gymnasium that permitted her to enter the University in 1901 to study science. She worked so hard that she successfully prepared for this exam in two years rather than the average four and at twenty two she became one of the few women students at the University of Vienna.
At the university she met with some rudeness from her fellow male students (a female student then being something unusual) but was inspired by her teachers, particularly Ludwig Boltzmann, who persuaded her to choose physics over mathematics.
Ludwig Eduard Boltzmann (February 20, 1844 – September 5, 1906) was an Austrian physicist and philosopher whose greatest achievement was in the development of statistical mechanics, which explains and predicts how the properties of atoms (such as mass, charge, and structure) determine the physical properties of matter (such as viscosity, thermal conductivity, and diffusion).
Lise’s university syllabus was heavy, filled with physics, chemistry, botany and calculus and she took over twenty five hours of courses a week. She was bored by lectures, but she was fascinated with the laboratory and as a result, and with Boltzmann’s suggestion, decided to pursue a career in physics.
Amongst the subjects Lisa studied were analytical mechanics, electricity and magnetism, elasticity and hydrodynamics, acoustics, optics, thermodynamics and kinetic theory.
After graduating Lise started her doctoral research and became only the second woman to obtain a doctoral degree in physics at the University of Vienna in 1905 (her dissertation was on “heat conduction in an inhomogeneous body”)
After graduation Lise remained in Vienna for a time as assistant to Boltzmann’s laboratory assistant because she had no other offers (she did however reject the offer of a job in a gas lamp factory). Universities at the time did not hire women researchers and even her application to work with Marie Curie was rejected. During this period 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 particles are slightly deflected in passing through matter.
Lise was also interested in theoretical physics and after Max Planck met her during a visit to Vienna and talked with her about quantum physics and radiation research she was inspired. So in the winter of 1907 with Planck’s encouragement she requested and obtained her father’s (very modest) financial support and left Vienna to go to the Institute for Experimental Physics in Berlin to study with him. She became very good friends with Planck’s two daughters, Emma and Grete.
She thought it would only be in Berlin for a year or two.
Max Karl Ernst Ludwig Planck, FRS (April 23, 1858 – October 4, 1947) was a German theoretical physicist who originated quantum theory, which won him the Nobel Prize in Physics in 1918.
Stefan Meyer (27 April 1872 – 29 December 1949) was an Austrian physicist involved in research on radioactivity. He became director of the Institute for Radium Research in Vienna and received the Lieben Prize in 1913 for his research on radium.
Lise enrolled for Planck’s lectures soon after arriving in Berlin, but had some difficulty finding a place to do experimental work until she met a young chemist named Otto Hahn at one of the weekly symposia, who was looking for a physicist to help him in his work on the chemistry of radioactivity.
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, Lise 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 (Fischer was scared of women and thought their hairstyles were a fire hazard but two years later, after women’s education had been regularized in Berlin, he welcomed Lise). Finally, Fischer allowed Lise and Hahn to set up a laboratory in a converted woodworking shop in the Institute’s basement for radiation measurements, as long as Lise agreed never to enter the higher floors of the building and entered the building through the back entrance. She wasn’t even allowed to use the lavatory and had to use one down the street.
In 1912 Lise joined the Kaiser-Wilhelm Institut für Chemie, newly opened in Berlin-Dahlem as Hahn had received an appointment in the small radioactivity department there and invited her to join him in his laboratory. Soon afterwards, Planck asked her to lecture as an assistant professor at the Institute for Theoretical Physics. The first woman in Germany to hold such a position, she drew several members of the news media to her opening lecture.
Hahn, the chemist, was primarily interested in the discovery of new elements and the examination of their properties, while Lise 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.
Hermann Emil Louis Fischer (9 October 1852 – 15 July 1919) was a German chemist and 1902 recipient of the Nobel Prize in Chemistry.
Otto Hahn, OBE, ForMemRS (8 March 1879 – 28 July 1968) was a German chemist and pioneer in the fields of radioactivity and radiochemistry who won the Nobel Prize in Chemistry in 1944 for the discovery of nuclear fission. He is regarded as one of the most significant chemists of all time and especially as “the father of nuclear chemistry”.
For the most part, however, the early days of the collaboration between Hahn and Meitner were filled with their investigations into the behaviour of beta rays as they passed through aluminium.
During the First World War Lise volunteered as a roentgenographic nurse with the Austrian army. On her leave she went back to Berlin to measure radioactive substances; Hahn’s leave 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 Lise 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. Because of Otto’s war service Lise did most of the work; however Hahn received all the credit. She asked him repeatedly to give her the recognition due her, but it never happened.
A few years later Lise received the Leibniz Medal from the Berlin Academic of Science and the Leibniz Prize from the Austrian Academy of Science for the discovery of protactinium.
In 1918, Lise 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 at that time to concentrate on research more suited to their individual training. For Lise, this constituted a return to beta radiation studies.
Lise kept up her links with the University of Berlin and in 1918 became a docent there. Her inaugural lecture was given in 1922; it concerned cosmic physics (reported in the press as “cosmetic physics”).
Misogyny continued to dog her and she often found that she was expected to escort the wives of visiting professors shopping. According to one famous anecdote, she was solicited to write an article by an encyclopaedia 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.
Docent is a title at some European universities to denote a specific academic appointment within a set structure of academic ranks below professor (i.e. professor ordinarius). Docent is also used at some universities generically for a person who has the right to teach. The term is derived from the Latin word docēns, which is the present active participle of docēre (to teach, to lecture). Becoming a docent is referred to as habilitation.
The photo shows the Danish physicist Niels Bohr at a “bonzenfreie Kolloquium” organised for him by Lise (shown facing Bohr) in Dahlem near Berlin in 1920.
Niels Henrik David Bohr (7 October 1885 – 18 November 1962) was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922.
Lise continued her work toward clarifying the relationships between beta and gamma rays and 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.
Jean Danysz (11 March 1884 – 4 November 1914) born Jan Kazimierz Danysz, was a French physicist of Polish extraction.
Danysz made considerable advances on the magnetic deflection techniques of Baeyer, Hahn and Meitner, placing the source (he used radium) in a capillary tube under a slit, with a photographic plate in the same horizontal plane.
In 1922, Lise discovered the cause, known as the Auger effect, of the emission from surfaces of electrons with ‘signature’ energies. The effect is named for Pierre Victor Auger, a French scientist who independently discovered the effect in 1923.
Pierre Victor Auger (14 May 1899 – 24 December 1993) was a French physicist, born in Paris. He worked in the fields of atomic physics, nuclear physics, and cosmic ray physics.
Lise 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.
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 1927 it was found, by Ellis and Wooster that each electron gives to its surrounding material an energy equal to the mean energy of the continuous spectrum, not its top energy as Lise had first thought. With Wilhelm Orthmann, she immediately set out to check the result and reported good agreement with their data in the paper that she and Orthmann published jointly in 1929.
Although her 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.
In 1932 Lise travelled to Munster to attend a meeting of the Bunsen society. In the above picture she is the third person on the left standing (between seated Geiger and Rutherford).
In a paper dated March 1933 she was one of the first to observe and report on positrons formed from gamma rays.
The above photograph shows the attendees at the Solvay Conference in 1933. Lise Meitner is the second from the right, seated. The other two women in the photo are Irene Joliot-Curie, seated second from the left, and Marie Curie, seated in the centre.
In the early 1930’s nuclear physics advanced dramatically: the neutron was discovered in 1932 by James Chadwick, the positron in 1933, and artificial radioactivity in 1934. Lise and her colleagues published a number of short papers in the light of these rapid developments. In 1934 Lise 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).
Throughout the 1930s, despite Albert Einstein calling Lise “our Madame Curie” and Wolfgang Pauli considering her “a really great scientist” and the superior of Hahn she failed to win a Nobel Prize despite being nominated for her work on beta decay.
During this time science funding changed for the “better”. Funding for physics equalled the funding for opera (now the funding for opera is 1000 times better) and Niels Bohr was funded by Carlsberg beer. Initially it was very poor.
Unfortunately Lise’s life was not improving. On the 20th January 1933 Hitler became chancellor of Germany. Immediately this became a problem for Jewish scientists, even in Austria before the Anschluss.
The Anschluss (German: Annexation or Connection) was the annexation of Austria by Nazi Germany in March 1938.
Almost immediately Jewish scientists were being dismissed. Lise briefly had some protection because she was Austrian, had been baptised a protestant and because Wilhelm Institute was not a government facility however it was her Jewish birth that counted. In the mid-1930s she had been asked to stop lecturing at the university but she continued her research.
In 1936 Lise was working on the problem of neutrons and uranium following up results obtained by Enrico 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 Lise set out to isolate such elements by precipitating an irradiated and acidified uranium salt solution with hydrogen sulphide in order to eliminate all elements between polonium (84) and uranium (92); they assumed that the remaining precipitate must contain only transuranic elements. 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.
Ida Noddack (25 February 1896 – 24 September 1978), née Ida Tacke, was a German chemist and physicist. She was the first to mention the idea of nuclear fission in 1934. With her husband Walter Noddack she discovered element 75, rhenium. She was nominated three times for the Nobel Prize in Chemistry.
Irène Joliot-Curie and Pavle Savitch were also doing similar work and 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 Lise and her colleagues could not confirm this finding. No matter how many times they bombarded uranium with neutrons, no thorium resulted. Hahn and Lise 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. Joliot-Curie had made a few mistakes one of which was that the chemistry of actinides was similar to transuranic elements
Lise had the opportunity of leaving Germany but didn’t because she thought things would change.
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. Her situation became desperate.
On July 13, 1938, Lise, with the support of Otto Hahn and the help from the Dutch physicists Dirk Coster and Adriaan Fokker, escaped to the Netherlands. She was forced to travel under cover to the Dutch border, where Coster persuaded German immigration officers that she had permission to travel to the Netherlands. She reached safety, though without her possessions. Lise later said that she left Germany forever with 10 marks in her purse. Before she left, Otto Hahn had given her a diamond ring he had inherited from his mother: this was to be used to bribe the frontier guards if required.
Lise was lucky to escape, as Kurt Hess, a chemist who was the head of the organic department of the KWI and an avid Nazi, had informed the authorities that she was about to flee. An appointment at the University of Groningen did not come through, and she went instead to Stockholm, where she took up a post at Manne Siegbahn’s laboratory where a cyclotron was being constructed, despite the difficulty caused by Siegbahn’s prejudice against women in science. Here she established a working relationship with Niels Bohr, who travelled regularly between Copenhagen and Stockholm. She continued to correspond with Hahn and other German scientists.
She had originally made temporary arrangements to work at the Institute of the Academy of Sciences under the sponsorship of a Nobel grant but by late autumn, however, Lise’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.
Also in 1938 Enrico Fermi found he had to leave Italy to escape new Italian Racial Laws that affected his Jewish wife Laura. He moved to the United States and became involved in the Manhattan project.
The Manhattan Project was a research and development project that produced the first atomic bombs during World War II.
Hahn and Lise continued consulting via letter with one secret meeting in Copenhagen in November 1938 to plan experiments. It was during this meeting that Lise was able to hear about further research done by Hahn and Fritz Strassmann on Joliot-Curie’s unusual results on bombarding Uranium with neutrons. 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. She began work out how uranium could possibly yield barium. When out walking soon after the meeting she paused for a rest on a log and began to work out a theory, sketching diagrams in the snow.
Her results were published in Nature on February 11, 1939. The paper was called “On the Products of the Fission of Uranium and Thorium”. She had discovered that when a uranium nucleus was struck by neutrons barium was produced. This was strange because barium is so much smaller than uranium, and so another explanation was needed. She and her nephew Otto Frisch then used Niels Bohr’s model of the nucleus to show the neutron inducing oscillations in the uranium nucleus. Sometimes the oscillating nucleus would stretch into a dumbbell shape. Also, sometimes the repulsive forces between the protons in the two rounded ends would cause the narrow waist in between to pinch off and leave two nuclei where there had only been one. Meitner described the process in a letter to the journal Nature and named it fission. The word “fission” was used because the description of the splitting of the nucleus seemed analogous to cell division.
The surviving correspondence between Lise and Hahn shows that Hahn recognized that fission was the only explanation for the barium (at first he named the process a ‘bursting’ of the uranium), but, baffled by this remarkable conclusion, he wrote to Lise. The possibility that uranium nuclei might break up under neutron bombardment had been suggested years before, notably by Ida Noddack in 1934. However, by employing the existing “liquid-drop” model of the nucleus, Lise and Frisch were the first to articulate a theory of how the nucleus of an atom could be split into smaller parts: uranium nuclei had split to form barium and krypton, accompanied by the ejection of several neutrons and a large amount of energy (the latter two products accounting for the loss in mass). She and Frisch had discovered the reason that no stable elements beyond uranium (in atomic number) existed naturally; the electrical repulsion of so many protons overcame the strong nuclear force. Frisch and Lise also first realized that Einstein’s famous equation, E = mc^2, explained the source of the tremendous releases of energy in nuclear fission, by the conversion of rest mass into kinetic energy, popularly described as the conversion of mass into energy.
Lise’s recognition of the principle of fission and her prediction of the existence of a chain reaction was momentous. When Frisch described the theory to Bohr, he slapped his head and said “Oh what idiots we’ve been.” Understanding the experimental results and knowing that the German’s had the information prompted action within the physics community and then the Allied governments. Lise was eventually offered a position with the Manhattan Project, which built on her work but she refused having no desire to work on a bomb.
Everyone in the physics community recognized what Lise had done. Although she wasn’t there for the final experimental results, she had originated the project, gathered the team, worked on it for almost 4 years, and interpreted the final results. Nevertheless, only months after publication Hahn began denying that Meitner had been an important part of the discovery at all. Then in 1944, the Nobel Committee voted secretly to give the Nobel Prize for Chemistry to Hahn, and Hahn alone, for the discovery of nuclear fission. No one disputed that Hahn deserved it, but everyone in the physics community knew that Meitner deserved a Nobel Prize as well.
In spite of the hurt of Hahn’s betrayal, and Lise’s intense criticism of the scientists who had collaborated with the Nazis, they remained friends.
She wanted her discoveries to be used for peaceful purposes. To her dismay, her research resulted in the dropping of atomic bombs on Hiroshima and Nagasaki in Japan to bring about the end of World War 2. After the bombs had been dropped the press hounded her
During her 60 years of work in the field of atomic physics she wrote 128 articles, served on scientific commissions, and served on the United Nations committee on atomic energy.
She and Eleanor Roosevelt in 1945 pledged to work together for world peace.
In 1946 Lise spent half a year in Washington, D. C., as a visiting professor at Catholic University. Whilst she was there she won “Woman of the year” given by the National Press Club. 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, she retired to Cambridge (UK) to be near relatives. In the following years, she won the Max Planck Medal and was awarded numerous honorary degrees from both American and European universities.
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. In 1966, two years before she died she received the Enrico Fermi Award along with her co-workers Strassman and Hahn.
Lise died on 27 October 1968 at the age of 89 and was buried in the village of Bramley in Hampshire, at St. James parish church.
In 1997, twenty-nine years after her death, the chemical element 109, the heaviest known element was named Meitnerium in her honour.
Her nephew Otto Frisch composed the inscription on her headstone. ” Lise Meitner: A physicist who never lost her humanity”.