Lise Meitner

Elise Meitner ( , ; 7 November 1878 – 27 October 1968) was an Austrian-Swedish physicist who was one of those responsible for the discovery of the element protactinium and nuclear fission. While working at the Kaiser Wilhelm Institute on radioactivity, she discovered the radioactive isotope protactinium-231 in 1917. In 1938, Meitner and her nephew, the physicist Otto Robert Frisch, discovered nuclear fission. She was praised by Albert Einstein as the "German Marie Curie".

Completing her doctoral research in 1905, Meitner became the second woman from the University of Vienna to earn a doctorate in physics. She spent most of her scientific career in Berlin, Germany, where she was a physics professor and a department head at the Kaiser Wilhelm Institute; she was the first woman to become a full professor of physics in Germany. She lost these positions in the 1930s because of the anti-Jewish Nuremberg Laws of Nazi Germany, and in 1938 she fled to Sweden, where she lived for many years, ultimately becoming a Swedish citizen.

In mid-1938, Meitner with chemists Otto Hahn and Fritz Strassmann at the Kaiser Wilhelm Institute found that bombarding thorium with neutrons produced different isotopes. Hahn and Strassmann later in the year showed that isotopes of barium could be formed by bombardment of uranium. In late December, Meitner and Frisch worked out the phenomenon of such a splitting process. In their report in February issue of ''Nature'' in 1939, they gave it the name "fission". This principle led to the development of the first atomic bomb during World War II, and subsequently other nuclear weapons and nuclear reactors.

Meitner did not share the 1944 Nobel Prize in Chemistry for nuclear fission, which was awarded exclusively to her long-time collaborator Otto Hahn. Several scientists and journalists have called her exclusion "unjust". According to the Nobel Prize archive, she was nominated 19 times for the Nobel Prize in Chemistry between 1924 and 1948, and 29 times for the Nobel Prize in Physics between 1937 and 1965. Despite not having been awarded the Nobel Prize, Meitner was invited to attend the Lindau Nobel Laureate Meeting in 1962. However, she received many other honours, including the naming of chemical element 109 meitnerium after her in 1997.

Early years

She was born Elise Meitner on 7 November 1878 into a Jewish upper-middle-class family at the family home in 27 Kaiser Josefstraße in the Leopoldstadt district of Vienna, the third of eight children of Hedwig and Philipp Meitner. The birth register of Vienna's Jewish community lists her as being born on 17 November 1878, but all other documents list her date of birth as 7 November, which is what she used. Her father was one of the first Jewish lawyers admitted to practice in Austria. She had two older siblings, Gisela and Auguste (Gusti), and four younger: Moriz (Fritz), Carola (Lola), Frida and Walter; all ultimately pursued an advanced education. Her father was a confirmed freethinker, and she was brought up as such. As an adult, she converted to Christianity, following Lutheranism, and was baptised in 1908; her sisters Gisela and Lola converted to Catholic Christianity that same year. She also adopted a shortened name "Lise".

Education

Meitner's earliest research began at age eight, when she kept a notebook of her records underneath her pillow. She was particularly drawn to mathematics and science, and first studied colours of an oil slick, thin films, and reflected light. Women were not allowed to attend public institutions of higher education in Vienna until 1897, and she completed her final year of school in 1892. Her education included bookkeeping, arithmetic, history, geography, science, French and gymnastics.

The only career available to women was teaching, so she trained as a French teacher. Her sister Gisela passed the '' Matura'', and entered medical school in 1900. In 1899, Meitner began taking private lessons with two other young women, cramming the missing eight years of secondary education into just two. Physics was taught by Arthur Szarvasy. In July 1901 the girls sat an external examination at the Akademisches Gymnasium. Only four out of fourteen girls passed, including Meitner and Henriette Boltzmann, the daughter of physicist Ludwig Boltzmann.

Meitner entered the University of Vienna in October 1901. She was particularly inspired by Boltzmann, and was said to often speak with contagious enthusiasm of his lectures. Her dissertation was supervised by Franz Exner and Hans Benndorf. Her thesis titled ''Prüfung einer Formel Maxwells'' ("''Examination of Maxwell's Formula''") was submitted on 28 November 1905, evaluated by Exner and Boltzmann, and approved on 28 November 1905. She became one of the first women to earn a doctoral degree in physics at the University of Vienna, after Olga Steindler who had received her degree in 1903. Her thesis was published as ''Wärmeleitung in inhomogenen Körpern'' ("''Thermal Conduction in Inhomogeneous Bodies''") on 22 February 1906.

Paul Ehrenfest asked her to investigate an article on optics by Lord Rayleigh that detailed an experiment that produced results that Rayleigh had been unable to explain. She was not only able to explain what was going on; she went further and made predictions based on her explanation, and then verified them experimentally, demonstrating her ability to carry out independent and unsupervised research.

While engaged in this research, Meitner was introduced by Stefan Meyer to radioactivity, then a very new field of study. She started with alpha particles. In her experiments with collimators and metal foil, she found that scattering in a beam of alpha particles increased with the atomic mass of the metal atoms. Later on, this led Ernest Rutherford to predict the nuclear atom. She submitted her findings to the ''Physikalische Zeitschrift'' on 29 June 1907.

Friedrich Wilhelm University

Encouraged and backed by her father's financial support, Meitner went to the Friedrich Wilhelm University, where the renowned physicist Max Planck taught. Planck invited her to his home, and allowed her to attend his lectures, which was an unusual gesture by Planck, who was on the record as opposing the admission of women to universities in general, but he was willing to admit that there was the occasional exception; apparently he recognised Meitner as one of the exceptions. She became friends with Planck's twin daughters Emma and Grete, who shared her love of music.

Attending Planck's lectures did not take up all her time, and Meitner approached Heinrich Rubens, the head of the experimental physics institute, about doing some research. Rubens said that he would be happy for her to work in his laboratory. He also added that Otto Hahn at the chemistry institute was looking for a physicist to collaborate with. A few minutes later she was introduced to Hahn. He had studied radioactive substances under Sir William Ramsay, and in Montreal under Rutherford, and was already credited with the discovery of what were then thought to be several new radioactive elements. (In fact, they were isotopes of known elements, but the concept of an isotope, along with the term, was only propounded by Frederick Soddy in 1913.) Hahn was the same age as herself, and she noted his informal and approachable manner. In Canada there had been no requirement to be circumspect when addressing the egalitarian New Zealander Rutherford, but many people in Germany found his manner offputting, and characterised him as an "Anglicised Berliner". In Montreal, Hahn had become accustomed to collaboration with physicists, including at least one woman, Harriet Brooks.

The head of the chemistry institute, Emil Fischer, placed a former woodworking shop (''Holzwerkstatt'') at Hahn's disposal in the basement to use as a laboratory. Hahn equipped it with electroscopes to measure alpha and beta particles and gamma rays. It was not possible to conduct research in the wood shop, but Alfred Stock, the head of the inorganic chemistry department, let Hahn use a space in one of his two private laboratories. Like Meitner, Hahn was unpaid, and lived off an allowance from his father, although somewhat larger than hers. He completed his habilitation in the spring of 1907, and became a ''Privatdozent''. Most of the organic chemists at the chemistry institute did not regard Hahn's work—detecting minute traces of isotopes too small to see, weigh or smell through their radioactivity—as real chemistry. One department head remarked that "it is incredible what one gets to be a ''Privatdozent'' these days!"

The arrangement was difficult for Meitner at first. Women were not yet admitted to universities in Prussia. Meitner was allowed to work in the wood shop, which had its own external entrance, but she could not set foot in the rest of the institute, including Hahn's laboratory space upstairs. If she wanted to go to the toilet, she had to use one at the restaurant down the street. The following year, women were admitted to Prussian universities, and Fischer lifted the restrictions, and had women's toilets installed in the building. Not all the chemists were happy about this. The Institute of Physics was more accepting, and she became friends with the physicists there, including , James Franck, Gustav Hertz, Robert Pohl, Max Planck, and Wilhelm Westphal.

During the first years Meitner worked together with Hahn they co-authored three papers in 1908, and six more in 1909. She also, together with 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. While Hahn was more concerned with discovering new elements (now known to be isotopes), Meitner was more concerned with understanding their radiations. She observed that radioactive recoil could be a new way of detecting radioactive substances. They set up some tests and soon discovered two more new isotopes.

Meitner was particularly interested in beta radiation. By this time, they were known to be electrons. Alpha particles were emitted with characteristic energy, and she expected that this would be true of beta particles too. Hahn and Meitner carefully measured the absorption of beta particles by aluminium, but the results were puzzling. In 1914, James Chadwick found that electrons emitted from the atomic nucleus formed a continuous spectrum, but Meitner found this hard to believe, as it seemed to contradict quantum physics.

Kaiser Wilhelm Institute for Chemistry

In 1912, Hahn and Meitner moved to the newly founded Kaiser Wilhelm Institute (KWI) for Chemistry. Hahn accepted an offer from Fischer to become a junior assistant in charge of its radiochemistry section, the first laboratory of its kind in Germany. The job came with the title of "professor" and a salary of 5,000 marks per annum. Meitner worked without salary as a "guest" in Hahn's section. Later that year, perhaps fearing that Meitner was in financial difficulties and might return to Vienna, since her father had died in 1910, Planck appointed her his assistant at the Institute for Theoretical Physics in the Friedrich Wilhelm University. As such, she marked his students' papers. It was her first paid position. Assistant was the lowest rung on the academic ladder, and Meitner was the first female scientific assistant in Prussia.

Proud officials presented Meitner to Kaiser Wilhelm II at the official opening of the KWI for Chemistry on 23 October 1912. The following year she became a ''Mitglied'' (associate), the same rank as Hahn (although her salary was still less), and the radioactivity section became the Hahn-Meitner Laboratory. Meitner celebrated with a dinner party at the Hotel Adlon. Hahn and Meitner's salaries would soon be dwarfed by royalties from mesothorium ("middle thorium", radium-228 also called "German radium") produced for medical purposes, for which Hahn received 66,000 marks in 1914, of which he gave ten percent to Meitner. In 1914, Meitner received an attractive offer of an academic position in Prague. Planck made it clear to Fischer that he didn't want Meitner to leave, and Fischer arranged for her salary to be doubled to 3,000 marks.

The move to new accommodation was fortuitous, as the wood shop had become thoroughly contaminated by radioactive liquids that had been spilt, and radioactive gases that had vented and then decayed and settled as radioactive dust, making sensitive measurements impossible. To ensure that their clean new laboratories stayed that way, Hahn and Meitner instituted strict procedures. Chemical and physical measurements were conducted in different rooms, people handling radioactive substances had to follow protocols that included not shaking hands, and rolls of toilet paper were hung next to every telephone and door handle. Strongly radioactive substances were stored in the old wood shop, and later in a purpose-built radium house on the institute grounds.

World War I and the discovery of protactinium

In July 1914—shortly before the outbreak of World War I in August—Hahn was called to active duty with the army in a '' Landwehr'' regiment. Meitner undertook X-ray technician training, and a course on anatomy at the city hospital in Lichterfelde. Meanwhile, she completed both the work on the beta ray spectrum that she had begun before the war with Hahn and Baeyer, and her own study of the uranium decay chain. In July 1915, she returned to Vienna, where she joined the Austrian Army as an X-ray nurse-technician. Her unit was soon deployed to the Eastern front in Poland, and she also served on the Italian front for a while before being discharged in September 1916.

Meitner returned to the KWI for Chemistry and her research in October. In January 1917, she was appointed the head of her own physics section. The Hahn-Meitner Laboratory was divided into separate Hahn and Meitner Laboratories, and her pay was increased to 4,000 marks. Hahn returned to Berlin on leave, and they discussed another loose end from their pre-war work: the search for the mother isotope of actinium. According to the radioactive displacement law of Fajans and Soddy, this had to be an isotope of the undiscovered element 91 on the periodic table that lay between thorium and uranium. Kasimir Fajans and Oswald Helmuth Göhring discovered this element in 1913, and named it ''brevium'' after its short half-life. However, the isotope they had found was a beta emitter, and therefore could not be the mother isotope of actinium. This had to be another isotope of the same element.

In 1914 Hahn and Meitner had developed a new technique for separating the tantalum group from pitchblende, which they hoped would speed the isolation of the new isotope. When Meitner resumed work in 1917, though, not only Hahn but most of the students, laboratory assistants and technicians had been called up, so Meitner had to do everything herself. In February, Meitner extracted 2 grams of silicon dioxide () from 21 grams of pitchblende. She set 1.5 grams aside and added a tantalum pentafluoride () carrier to the other 0.5 grams, which she dissolved in hydrogen fluoride (). She then boiled it in concentrated sulfuric acid (), precipitated what was believed to be element 91, and verified that it was an alpha emitter. Hahn came home on leave in April, and together they devised a series of indicator tests to eliminate other known alpha emitters. The only known ones with similar chemical behaviour were lead-210 (which decays to alpha emitter polonium-210) and thorium-230.

For this more pitchblende was required. Meitner went to Vienna, where she met with Stefan Meyer. The export of uranium from Austria was forbidden due to wartime restrictions, but Meyer was able to offer her a kilogram of uranium residue, pitchblende from which the uranium had been removed, which was actually better for her purpose. The indicator tests showed that the alpha activity was not due to these substances. All that now remained was to find evidence of actinium. For this more pitchblende was required, and this time Meyer was unable to assist, as the export was now prohibited. Meitner managed to obtain 100 g of "double residue"—pitchblende without uranium or radium—from Friedrich Oskar Giesel and began tests with 43 grams of it, but its composition was different, and at first her tests did not work. With Giesel's help, she was able to produce a pure product that was strongly radioactive. By December 1917 she was able to isolate both the mother isotope and its actinium daughter product. She submitted their findings for publication in March 1918.

Although Fajans and Göhring had been the first to discover the element, custom required that an element was represented by its longest-lived and most abundant isotope, and brevium did not seem appropriate. Fajans agreed to Meitner naming the element "protoactinium" (subsequently shortened to protactinium), and assigning it the chemical symbol Pa. In June 1918, Soddy and John Cranston announced that they had independently extracted a sample of the isotope, but unlike Meitner they were unable to describe its characteristics. They acknowledged Meitner's priority, and agreed to the name. The connection to uranium remained a mystery, as neither of the known isotopes of uranium decayed into protactinium. It remained unsolved until the mother isotope, uranium-235, was discovered in 1929.

Beta radiation

In 1921, Meitner accepted an invitation from Manne Siegbahn to come to Sweden and give a series of lectures on radioactivity as a visiting professor at Lund University

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