Lise Meitner

Lise Meitner an Austrian-Swedish physicist (1878-1968) who played a central part in the discovery of nuclear fission. Although she was excluded from the Nobel Prize awarded for that discovery, her theoretical interpretation of the fission process made her one of the most important nuclear physicists of the twentieth century.

Early Life and Education

Lise Meitner was born in 1878 in Vienna, the daughter of a lawyer, and grew up in an assimilated Jewish family that valued education and music. Because girls in Austria were not then admitted to the university preparatory schools, she was educated privately and passed the external examination that allowed her to enter the University of Vienna, where she studied physics and mathematics.

She received her doctorate in 1906, one of the first women to do so in physics at Vienna, with a thesis on the conduction of heat in solids. She then went to Berlin to study with Max Planck, who had initially been reluctant to admit a woman to his lectures, and she soon became his assistant. In Berlin she met the chemist Otto Hahn, beginning a partnership that lasted more than thirty years.

As a woman and a Jew, she faced obstacles throughout her career. For years she worked without salary and in a converted workshop, denied full academic standing, and only in 1926 did she receive a professorial appointment at the University of Berlin. Her collaboration with Hahn produced a long series of discoveries in radioactivity and nuclear physics.

Radioactivity and Nuclear Physics

Meitner and Hahn investigated the radioactive substances produced by the decay of uranium and thorium, and together they discovered several new isotopes, including protactinium, whose isolation in 1917 established their reputation. Her physical insight and his chemical skill made an unusually effective combination, and their laboratory became a leading centre of radioactivity research.

She studied the beta decay of nuclei and the emission of electrons, and she made important contributions to the theory of the process. She was among the first to understand that the energy released in radioactive decay could be explained by the conversion of mass, and her careful measurements provided material for the development of nuclear theory.

In 1938, when Austria was annexed by Germany, she was forced to flee because of her Jewish ancestry. She escaped to the Netherlands and then to Sweden, where she found a place at the Nobel Institute in Stockholm. The separation from her laboratory was painful, and she continued to work under difficult and poorly funded conditions for the rest of her career.

The Discovery and Interpretation of Fission

In late 1938 Hahn and Fritz Strassmann, working in Berlin, bombarded uranium with neutrons and found barium among the products, a result that seemed impossible if the nucleus had merely captured a neutron. Hahn wrote to Meitner describing the puzzle, and she discussed it with her nephew Otto Frisch during a walk in the Swedish countryside over the Christmas holidays.

Meitner recognised that the uranium nucleus could split into two roughly equal parts, a process for which she and Frisch coined the term fission. She applied the liquid drop model of the nucleus, in which protons and neutrons behave like the molecules of a fluid, and calculated that the electrical repulsion of the two fragments would release a large amount of energy, exactly as the measured mass difference indicated.

The interpretation of fission was published in early 1939 and immediately transformed nuclear physics. It explained the Berlin experiments, predicted the release of enormous energy and suggested that further neutrons would be emitted, making a chain reaction possible. Meitner and Frisch had provided the theoretical key to one of the decisive discoveries of the century, and the news spread rapidly through the scientific world.

War, Ethics and the Refusal of the Bomb

During the Second World War Meitner was invited to join the Allied project to build an atomic bomb, and she refused. She was appalled by the prospect of a weapon of such destructive power and by the use to which nuclear energy might be put, and she chose to remain in Sweden, continuing her research on nuclear reactions while declining to work on weapons.

In 1944 the Nobel Prize in Chemistry was awarded to Otto Hahn alone for the discovery of fission, and Meitner's exclusion has been debated ever since. The decision, made by a committee that may have been influenced by her sex, her exile and a misunderstanding of her contribution, was a lasting reproach and helped to make her a symbol of the overlooked achievements of women in science.

She was invited to lead the physics section of the new atomic energy research in Sweden after the war, and she later moved to Britain. She received the Enrico Fermi Award in 1966 in recognition of her work, and she was honoured by many scientific bodies, though she never received the prize that many felt was hers.

Influence and Legacy

Meitner's scientific work ranged across the whole of nuclear physics, from radioactivity and beta decay to the theory of fission and the structure of the nucleus. She was among the most respected physicists of her generation, and even those who disagreed with the Nobel decision described her as the intellectual leader of the Berlin group.

Beyond her research she was a woman of wide culture, a lover of music and a determined opponent of the misuse of science. She conducted herself with dignity under persecution and exile, and in her later years she devoted herself to the education of the public about the promise and the danger of nuclear energy. The element meitnerium is named in her honour.

She died in 1968 in Cambridge, England. Her story has become central to the history of women in science, and her refusal to join the weapons project, together with her insistence on the peaceful uses of nuclear power, has given her a moral as well as a scientific standing. Her theoretical insight remains one of the foundations of the nuclear age.

See also

• Nuclear fission
• Otto Hahn
• Radioactivity
• Otto Frisch