Презентация "Lise Meitner"

7 November 1878 – 27 October 1968

Lise Meitner

• Lise Meitner was an Austrian-Swedish physicist who worked on radioactivity and nuclear physics. Otto Hahn and Meitner led the small group of scientists who first discovered nuclear fission of uranium when it absorbed an extra neutron; the results were published in early 1939.

• Meitner and Otto Frisch understood that the fission process, which splits the atomic nucleus of uranium into two smaller nuclei, must be accompanied by an enormous release of energy. This process is the basis of the nuclear weapons that were developed in the U.S. during World War II and used against Japan in 1945. Nuclear fission is also the process exploited by nuclear reactors to generate electricity.

Early years

• She was born Elise Meitner on 7 November 1878 into a Jewish upper-middle-class family in Vienna, 2nd district (Leopoldstat), the third of eight children. Her father Philipp Meitner was one of the first Jewish lawyers in Austria.She shortened her name from Elise to Lise. The birth register of Vienna's Jewish community lists Meitner as being born on 17 November 1878, but all other documents list her date of birth as 7 November, which is what she used. As an adult, she converted to Christianity, following Lutheranism, and was baptized in 1908.

Scientific career

• After one year of attending Planck's lectures, Meitner became Planck's assistant. During the first years she worked together with chemist Otto Hahn and together with him discovered several new isotopes.

• In 1909 she presented two papers on beta-radiation. She also, together with Otto Hahn, discovered and developed a physical separation method known as radioactive recoil, in which a daughter nucleus is forcefully ejected from its matrix as it recoils at the moment of decay.

• In 1917, she and Hahn discovered the first long-lived isotope of the element protactinium, for which she was awarded the Leibniz Medal by the Berlin Academy of Sciences. That year, Meitner was given her own physics section at the Kaiser Wilhelm Institute for Chemistry.

• In 1922, she discovered the cause of the emission from surfaces of electrons with 'signature' energies, known as the Auger effect. The effect is named for Pierre Victor Auger, a French scientist who independently discovered the effect in 1923.

• In 1926, Meitner became the first woman in Germany to assume a post of full professor in physics, at the University of Berlin.

• In 1935, as head of the physics department of the Kaiser Wilhelm Institute for Chemistry in Berlin-Dahlem (today the Hahn-Meitner Building of the Free University) she and Otto Hahn, the director of the KWI, undertook the so-called "transuranium research" program. This program eventually led to the unexpected discovery of nuclear fission of heavy nuclei in December 1938, half a year after she had left Berlin. She was praised by Albert Einstein as the "German Marie Curie".

• While at the Kaiser Wilhelm Institute, Meitner corresponded with James Chadwick at the Cavendish Laboratory at Cambridge. As Chadwick and others were attempting to prove the existence of the neutron, Meitner sent Polonium to Chadwick for his experiments. Chadwick eventually required and received more polonium for his experiments from a hospital in Baltimore, but he would remain grateful to Meitner. Later, he said he was "quite convinced that [Meitner] would have discovered the neutron if it had been firmly in her mind, if she had had the advantage of, say, living in the Cavendish for years, as I had done."

• In 1930, Meitner taught a seminar on nuclear physics and chemistry with Leó Szilárd. After the discovery of the neutron in the early 1930s, the scientific community speculated that it might be possible to create elements heavier than uranium (atomic number 92) in the laboratory. A scientific race began between the teams of Ernest Rutherford in Britain, Irène Joliot-Curie in France, Enrico Fermi in Italy, and Meitner and Hahn in Berlin. At the time, all concerned believed that this was abstract research for the probable honour of a Nobel prize. None suspected that this research would culminate in nuclear weapons.

• When Adolf Hitler came to power in 1933, Meitner was still acting as head of the physics department of the Kaiser Wilhelm Institute for Chemistry. Although she was protected by her Austrian citizenship, all other Jewish scientists, including Szilárd, Fritz Haber, her nephew Otto Frisch, and many other eminent figures, were dismissed or forced to resign from their posts. Most of them emigrated from Germany. Her response was to say nothing and bury herself in her work. After the Anschluss in March 1938, her situation became difficult.

• On July 13, 1938, Meitner, with the support of Otto Hahn and the help from the Dutch physicists Dirk Coster and Adriaan Fokker, departed for the Netherlands.

Nuclear fission

• On occasion of a lecture by Hahn in Niels Bohr's Institute he, Bohr, Meitner and Frisch met in Copenhagen on November 10, 1938. Later they continued to exchange a series of letters. In December Hahn and his assistant Fritz Strassmann performed the difficult experiments which isolated the evidence for nuclear fission at their laboratory in Berlin-Dahlem. The surviving correspondence shows that Hahn recognized that 'fission' was the only explanation for the proof of barium (at first he named the process a 'bursting' of the uranium), but, baffled by this remarkable conclusion, he wrote to Meitner. 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, Meitner and Frisch, exclusively informed by Hahn in advance, were therefore 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 . They 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. Ironically, Meitner was motivated to begin these calculations in order to show that Irene Joliot-Curie's interpretation of some experiments violated the liquid drop model.