Otto Hahn (German: [ˈɔtoː ˈhaːn]; 8 March 1879 – 28 July 1968) was a German chemist who helped develop the field of radiochemistry. He is known as the father of nuclear chemistry and the discoverer of nuclear fission, the process that powers nuclear reactors and nuclear weapons. Hahn and Lise Meitner studied radioactive elements such as radium, thorium, protactinium, and uranium. He also discovered the effects of atomic recoil and nuclear isomerism and helped create a method called rubidium–strontium dating. In 1938, Hahn, Meitner, and Fritz Strassmann discovered nuclear fission. Hahn received the 1944 Nobel Prize in Chemistry for this work.

Otto Hahn graduated from the University of Marburg and earned a doctorate in 1901. He studied under Sir William Ramsay at University College London and under Ernest Rutherford at McGill University in Canada, where he found new radioactive isotopes. He returned to Germany in 1906 and used a former woodworking shop in Berlin as a laboratory. Hahn completed his habilitation in 1907 and became a Privatdozent. In 1912, he led the Radioactivity Department at the Kaiser Wilhelm Institute for Chemistry (KWIC). He worked with Lise Meitner in a building named after them, and together they made important discoveries, including Meitner isolating the longest-lived isotope of protactinium in 1918.

During World War I, Hahn served in a military unit on the Western Front and with a chemical warfare group led by Fritz Haber on multiple fronts. He earned the Iron Cross (2nd Class) for his role in the First Battle of Ypres. After the war, he became head of KWIC while managing his own department. From 1934 to 1938, Hahn worked with Strassmann and Meitner to study isotopes formed when uranium and thorium were bombarded with neutrons, leading to the discovery of nuclear fission. He opposed the Nazi Party and its persecution of Jews, which caused many of his colleagues, including Meitner, to leave Germany. Despite this, during World War II, Hahn worked on the German nuclear weapons program, studying the results of uranium fission. After the war, he was arrested by Allied forces and held in Farm Hall with other German scientists from July 1945 to January 1946.

Hahn was the last president of the Kaiser Wilhelm Society for the Advancement of Science in 1946 and the first president of its successor, the Max Planck Society, from 1948 to 1960. In 1959, he helped create the Federation of German Scientists, a group that promoted responsible scientific practices. As he rebuilt German science after the war, Hahn became one of the most respected citizens of post-war West Germany.

Early life and education

Otto Hahn was born in Frankfurt am Main on March 8, 1879. He was the youngest son of Heinrich Hahn, a successful glassmaker who started the Glasbau Hahn company, and Charlotte Hahn (née Giese). Otto had an older half-brother, Karl, who was his mother’s son from a previous marriage, and two older brothers, Heiner and Julius. The family lived above his father’s workshop. The three younger boys attended the Klinger Oberrealschule in Frankfurt. At age 15, Otto became interested in chemistry and did simple experiments in the laundry room of their home. His father wanted him to study architecture, as he owned several buildings, but Otto convinced him that he wanted to become an industrial chemist.

In 1897, after passing his final exams, Hahn began studying chemistry at the University of Marburg. He also studied math, physics, mineralogy, and philosophy. He joined a student group for science and medicine, which later became known as the Landsmannschaft Nibelungi. During his third and fourth semesters, he studied at the University of Munich, where he learned organic chemistry from Adolf von Baeyer, physical chemistry from Wilhelm Muthmann, and inorganic chemistry from Karl Andreas Hofmann. In 1901, Hahn earned his doctorate from Marburg for a paper titled "On Bromine Derivatives of Isoeugenol," a topic in classical organic chemistry. He completed one year of military service (instead of the usual two, due to his doctorate) in the 81st Infantry Regiment but did not seek a military commission. Afterward, he returned to Marburg, where he worked for two years as an assistant to his doctoral advisor, Professor Theodor Zincke.

Early career in London and Canada

Otto Hahn still wanted to work in industry. He received a job offer from Eugen Fischer, who was the director of Kalle & Co. (and the father of chemist Hans Fischer). A condition of the job was that Hahn had to have lived in another country and speak another language well. To meet this requirement and improve his English, Hahn accepted a position at University College London in 1904. He worked under Sir William Ramsay, a scientist who discovered the noble gases. At London, Hahn studied radiochemistry, a new field at the time. In early 1905, while working with radium salts, Hahn discovered a new substance he called radiothorium (thorium-228). At the time, scientists believed this was a new radioactive element, but it was later found to be an isotope of thorium. The term "isotope" was first used in 1913 by British chemist Frederick Soddy.

Ramsay was excited about the discovery and planned to announce it formally. Following tradition, he shared the news with the Royal Society, a respected scientific group. On March 16, 1905, Ramsay presented Hahn’s findings to the Royal Society. The Daily Telegraph reported the discovery to its readers. Hahn published his results in the Proceedings of the Royal Society on May 24, 1905. This was the first of over 250 scientific papers he wrote about radiochemistry. When Hahn was ready to leave London, Ramsay asked about his future plans. Hahn mentioned the job offer from Kalle & Co. Ramsay encouraged him to pursue radiochemistry and suggested he move to the University of Berlin. Ramsay wrote to Emil Fischer, the head of the chemistry department there, who agreed to let Hahn work in his lab but said he could not become a Privatdozent because radiochemistry was not taught at the university. Hahn decided he needed more knowledge about the field and wrote to Ernest Rutherford, a leading expert. Rutherford agreed to take Hahn as an assistant, and Hahn’s parents agreed to cover his expenses.

From September 1905 until mid-1906, Hahn worked with Rutherford’s team in the basement of the Macdonald Physics Building at McGill University in Montreal. Some scientists doubted whether radiothorium existed. Bertram Boltwood humorously called it a compound of thorium X and "stupidity." Boltwood later agreed it existed, though he and Hahn disagreed about its half-life. Scientists William Henry Bragg and Richard Kleeman found that alpha particles from radioactive materials always had the same energy, which helped identify them. Hahn used this method to study radiothorium. He discovered that thorium A (polonium-216) and thorium B (lead-212) also contained a short-lived substance he named thorium C (later identified as polonium-212). He could not separate it and concluded it had a very short half-life (about 300 nanoseconds). Hahn also identified radioactinium (thorium-227) and radium D (later identified as lead-210). Rutherford praised Hahn, saying, "Hahn has a special nose for discovering new elements."

Chemical Institute in Berlin

In 1906, Hahn returned to Germany, where Fischer provided him with a former woodworking shop (Holzwerkstatt) in the basement of the Chemical Institute to use as a laboratory. Hahn added electroscopes to measure alpha and beta particles and gamma rays. In Montreal, these devices had been made from old coffee tins, but in Berlin, Hahn created them from brass with aluminum strips insulated using amber. He charged the electroscopes by rubbing hard rubber sticks against the sleeves of his suit. Research could not be done in the wood shop, but Alfred Stock, the head of the inorganic chemistry department, allowed Hahn to use space in one of his private laboratories. Hahn bought two milligrams of radium from Friedrich Oskar Giesel, the discoverer of emanium (radon), for 100 marks per milligram (equivalent to €700 in 2021). He also received thorium for free from Otto Knöfler, whose Berlin company was a major producer of thorium products.

Within a few months, Hahn discovered mesothorium I (radium-228), mesothorium II (actinium-228), and independently identified the parent substance of radium, ionium (later known as thorium-230). Later, mesothorium I became important for medical radiation treatments because it was as effective as radium-226 (discovered by Pierre and Marie Curie) but less expensive to produce. Hahn also found that, just as he could not separate thorium from radiothorium, he could not separate mesothorium I from radium.

In Canada, there was no need to be cautious when speaking to the egalitarian New Zealander Rutherford, but many in Germany found his behavior unsettling and described him as an "Anglicised Berliner." Hahn completed his habilitation in early 1907 and became a Privatdozent. A thesis was not required; instead, the Chemical Institute accepted one of his publications on radioactivity. Many organic chemists at the institute did not consider Hahn's work real chemistry. Fischer disagreed with Hahn's claim during his habilitation colloquium that radioactive substances existed in such tiny amounts they could only be detected by their radioactivity, arguing that he had always used his sense of smell to detect substances. However, Fischer eventually agreed. A department head remarked, "It is incredible what one gets to be a Privatdozent these days!"

Physicists were more accepting of Hahn's work, and he began attending a colloquium at the Physics Institute led by Heinrich Rubens. At one of these meetings on 28 September 1907, Hahn met Lise Meitner, an Austrian physicist. She was nearly his age, the second woman to earn a doctorate from the University of Vienna, and had already published two papers on radioactivity. Rubens suggested she could be a collaborator. This began a thirty-year partnership and lifelong friendship between the two scientists.

In Montreal, Hahn had worked with physicists, including Harriet Brooks, a woman. However, Meitner initially faced challenges in Germany because women were not yet admitted to universities in Prussia. She was allowed to work in the wood shop, which had an external entrance, but could not enter the rest of the institute, including Hahn's laboratory upstairs. If she needed to use the restroom, she had to go to a restaurant nearby. The following year, women were admitted to universities, and Fischer removed the restrictions, installing women's restrooms in the building.

Harriet Brooks observed radioactive recoil in 1904 but misinterpreted it. Hahn and Meitner correctly demonstrated that radioactive recoil occurs during alpha particle emission. Hahn studied a report by Stefan Meyer and Egon Schweidler about a decay product of actinium with a half-life of about 11.8 days. He identified it as actinium X (radium-223). He also discovered that when a radioactinium (thorium-227) atom emits an alpha particle, it does so with great force, causing actinium X to recoil. This recoil frees it from chemical bonds, gives it a positive charge, and allows it to be collected at a negative electrode.

Hahn was focused on actinium, but after reading his paper, Meitner pointed out that he had discovered a new method for detecting radioactive substances. They conducted tests and identified actinium C'' (thallium-207) and thorium C'' (thallium-208). Physicist Walther Gerlach called radioactive recoil "a profoundly significant discovery in physics with far-reaching consequences."

Kaiser Wilhelm Institute for Chemistry

In 1910, Hahn became a professor after being chosen by the Prussian Minister of Culture and Education, August von Trott zu Solz. Two years later, Hahn became the head of the Radioactivity Department at the newly created Kaiser Wilhelm Institute for Chemistry (KWIC) in Berlin-Dahlem, which is now called the Hahn-Meitner-Building of the Free University of Berlin. His yearly salary was 5,000 marks, which was equal to about €29,000 in 2021. In 1914, he received 66,000 marks (about €369,000 in 2021) from Knöfler for the mesothorium process. He gave 10 percent of this money to Meitner. The new institute was opened on 23 October 1912 in a ceremony led by Kaiser Wilhelm II. The Kaiser saw glowing radioactive substances in a dark room during the event.

Moving to the new building was helpful because the old wood shop had become very dirty with radioactive liquids that spilled and radioactive gases that settled as dust. This made it hard to do precise experiments. To keep their new labs clean, Hahn and Meitner created strict rules. Chemical and physical tests were done in separate rooms. People handling radioactive materials had to follow rules, like not shaking hands. Toilet paper rolls were placed near every telephone and door handle. Strongly radioactive materials were stored in the old wood shop and later in a special building on the institute grounds.

In July 1914, just before World War I began, Hahn was called back to serve in the army in a Landwehr regiment. He marched through Belgium, where the group he led used captured machine guns. He was given the Iron Cross (2nd Class) for his role in the First Battle of Ypres. He took part in the Christmas truce of 1914 and was made a lieutenant. In early 1915, he met chemist Fritz Haber, who explained his plan to use chlorine gas to break the stalemate in trenches. Hahn pointed out that the Hague Convention banned poison gas in projectiles, but Haber said the French already used tear gas in grenades and planned to release gas from cylinders instead of shells.

Haber’s unit was called Pioneer Regiment 35. After short training in Berlin, Hahn, along with physicists James Franck and Gustav Hertz, went back to Flanders to find a spot for the first gas attack. Hahn did not see the attack because he and Franck were choosing a location for the next one. Later, in Poland, at the Battle of Bolimów on 12 June 1915, they released a mix of chlorine and phosgene gas. Some German soldiers hesitated when the gas blew back toward them, so Hahn led them across No Man’s Land. He saw Russian soldiers suffering from the gas and tried to help some with gas masks, but failed. On 7 July, the gas again blew back on German lines, and Hertz was poisoned. Hahn’s work was interrupted by missions in Flanders and later at Verdun in 1916, where he helped introduce phosgene-filled shells to the Western Front. He continued searching for places to use gas attacks on both fronts. In December 1916, he joined a new gas command unit at Imperial Headquarters.

Between battles, Hahn returned to Berlin, where he worked with Meitner in their old laboratory. In September 1917, he was one of three officers, dressed in Austrian uniforms, sent to the Isonzo front in Italy to find a place for an attack using new weapons called rifled minenwerfers that launched hundreds of poison gas containers at enemy targets. They chose a site where Italian trenches were in a deep valley so the gas cloud would stay. The Battle of Caporetto broke the Italian lines, and the Central Powers took over much of northern Italy. That summer, Hahn was accidentally poisoned by phosgene while testing a new gas mask. At the end of the war, he was in the field in civilian clothes on a secret mission to test a device that heated and released a cloud of arsenicals.

In 1913, chemists Frederick Soddy and Kasimir Fajans discovered that alpha decay made atoms move two places down the periodic table, while losing two beta particles brought them back to their original position. This changed how the periodic table was organized, placing radium in group II, actinium in group III, thorium in group IV, and uranium in group VI. This left a gap between thorium and uranium. Soddy predicted an unknown element, which he called "ekatantalium," would be an alpha emitter with properties like tantalum. Soon after, Fajans and Oswald Helmuth Göhring found this element as a decay product of thorium. Based on their radioactive displacement law, they named it "brevium" because of its short half-life. However, since it was a beta emitter, it could not be the parent isotope of actinium. Another isotope of the same element had to be the parent.

Hahn and Meitner searched for the missing parent isotope. They developed a new method to separate the tantalum group from pitchblende, hoping to find the isotope faster. Their work was interrupted by World War I. Meitner became an X-ray nurse in Austrian Army hospitals but returned to the institute in October 1916. Hahn joined the gas command unit in Berlin in December 1916 after traveling between fronts and other locations from mid-1914 to late 1916.

Most students and lab workers were called to serve in the military, so Hahn and Meitner had to do all the work themselves. By December 1917, Meitner isolated the substance and proved it was the missing isotope. She and Hahn published their findings in March 1918 in the scientific journal Physikalischen Zeitschrift under the title Die Muttersubstanz des Actiniums; Ein Neues Radioaktives Element von Langer Lebensdauer ("The Mother Substance of Actinium; A New Radioactive Element with a Long Lifetime"). Even though Fajans and Göhring discovered the element

Nazi Germany

Fritz Strassmann went to the KWIC to study with Hahn to help improve his job chances. After the Nazi Party (NSDAP) took control of Germany in 1933, Strassmann refused a high-paying job offer because it required political training and membership in the Nazi Party. Later, he quit his position in the Society of German Chemists when the group became part of the Nazi German Labour Front. Because of this, Strassmann could not work in the chemical industry or earn his habilitation, which was needed for an academic job. Meitner convinced Hahn to hire Strassmann as an assistant. Soon, Strassmann was listed as a third collaborator on their research papers and sometimes even appeared first on the list.

Hahn visited the United States and Canada from February to June 1933 as a guest professor at Cornell University. He gave an interview to the Toronto Star Weekly where he spoke positively about Adolf Hitler.

The April 1933 Law for the Restoration of the Professional Civil Service banned Jews and communists from working in academia. Meitner was not affected because she was an Austrian citizen, not a German one. Haber was also not affected because he was a World War I veteran, but he resigned as director of the Kaiser Wilhelm Institute of Physical Chemistry and Electrochemistry on 30 April 1933 in protest. Other directors of Kaiser Wilhelm Institutes followed the new law, which applied to the KWS as a whole and institutes with more than 50% state support. This meant the KWI for Chemistry was not affected. Hahn did not have to fire any of his full-time staff, but as acting director of Haber’s institute, he dismissed a quarter of its staff, including three department heads. Gerhart Jander became the new director of Haber’s old institute and shifted its focus to chemical warfare research.

Like other KWS institute directors, Haber had saved a large amount of money to use freely. He wanted this money to help dismissed staff leave Germany. Hahn arranged for 10% of the funds to go to Haber’s former staff and the rest to the KWS, but the Rockefeller Foundation insisted the money be used for scientific research or returned. In August 1933, KWS administrators learned that boxes of equipment funded by the Rockefeller Foundation were being sent to Herbert Freundlich, one of the dismissed staff members now working in England. Ernst Telschow, a Nazi Party member, was in charge while Planck, the KWS president since 1930, was on vacation. Telschow ordered the shipment stopped. Hahn agreed but disagreed with the decision, believing foreign funds should not support military research, which the KWS was increasingly doing. When Planck returned from vacation, he told Hahn to speed up the shipment.

Haber died on 29 January 1934. A memorial service was held one year later. University professors were not allowed to attend, so they sent their wives instead. Hahn, Planck, and Joseph Koeth attended and gave speeches. Planck, who was older, did not run for re-election and was replaced in 1937 by Carl Bosch, a Nobel Prize winner in Chemistry and chairman of IG Farben, a company that supported the Nazi Party since 1932. Telschow became Secretary of the KWS. He supported the Nazis but was loyal to Hahn, who had once been his teacher. Hahn welcomed Telschow’s appointment. Hahn’s chief assistant, Otto Erbacher, became the KWI for Chemistry’s party representative (Vertrauensmann).

While Hahn was in North America in 1905–1906, he studied a mica-like mineral from Manitoba that contained rubidium. He examined how rubidium-87 decays radioactively and estimated its half-life as 2 x 10 years. He realized that by comparing the amount of strontium (which was once rubidium) in the mineral to the remaining rubidium, he could estimate the mineral’s age, assuming his calculation was correct. This method was better than using uranium decay, because some uranium turns into helium, which escapes and makes rocks seem younger than they are. Jacob Papish helped Hahn obtain several kilograms of the mineral.

In 1937, Strassmann and Ernst Walling extracted 253.4 milligrams of strontium carbonate from 1,012 grams of the mineral. All of it was the strontium-87 isotope, showing it had formed from the decay of rubidium-87. The mineral’s age had been estimated as 1,975 million years using uranium from the same deposit, which suggested the rubidium-87 half-life was 2.3 x 10 years—very close to Hahn’s original estimate. Rubidium-strontium dating became a common method for dating rocks in the 1950s, when mass spectrometry became widely used.

After James Chadwick discovered the neutron in 1932, Irène Curie and Frédéric Joliot used alpha particles to irradiate aluminum foil. They found that this created a short-lived radioactive isotope of phosphorus. They observed that positron emission continued even after neutron emissions stopped. This discovery showed a new type of radioactive decay and created a radioactive isotope from a non-radioactive element. Radiochemistry was no longer limited to heavy elements but applied to all elements on the periodic table. Chadwick noted that neutrons, being neutral, could enter atomic nuclei more easily than protons or alpha particles. Enrico Fermi and his team in Rome used this idea to irradiate elements with neutrons.

The radioactive displacement law by Fajans and Soddy stated that beta decay moves isotopes one element up on the periodic table, while alpha decay moves them two elements down. When Fermi’s group bombarded uranium atoms with neutrons, they found a complex mix of half-lives. Fermi concluded that new elements with atomic numbers greater than 92 (called transuranium elements) had been created. Meitner and Hahn had not worked together for many years, but Meitner wanted to study Fermi’s results. Hahn was initially uninterested but changed his mind after Aristid von Grosse suggested the findings might be an isotope of protactinium. They worked to confirm whether the 13-minute isotope was indeed protactinium.

Between 1934 and 1938, Hahn, Meitner, and Strassmann discovered many radioactive transmutation products, which they considered transuranic. At the time, actinides were not yet known, and uranium was mistakenly thought to be a group 6 element like tungsten. This led them to believe the first transuranic elements would resemble group 7 to 10 elements, such as rhenium and platinoids. They identified multiple isotopes of at least four such elements and (incorrectly) labeled them as

Post-war

On 25 April 1945, a group of British and American soldiers from the Alsos Mission arrived in Tailfingen, Germany, and surrounded the KWIC laboratory. Otto Hahn was told he was under arrest. When asked about his work on uranium, Hahn said, "I have them all here," and handed over 150 reports. He was taken to Hechingen, where he joined other scientists, including Erich Bagge, Horst Korsching, Max von Laue, Carl Friedrich von Weizsäcker, and Karl Wirtz. They were then moved to an old castle in Versailles, France, where they learned about the German surrender signed on 7 May 1945. Over the next few days, more scientists, such as Kurt Diebner, Walther Gerlach, Paul Harteck, and Werner Heisenberg, joined them. All were physicists except Hahn and Harteck, who were chemists. Most had worked on Germany’s nuclear weapons program, though von Laue knew about it but did not participate.

They were later moved to a castle in Modave, Belgium, where Hahn wrote about his life. On 3 July 1945, they were flown to England and arrived at Farm Hall near Cambridge. While there, all their conversations were secretly recorded using hidden microphones. They were given British newspapers, which Hahn read. He was upset by reports about the Potsdam Conference, where Germany lost territory to Poland and the USSR. In August 1945, the scientists learned about the atomic bombing of Hiroshima. Until then, most believed their nuclear project was more advanced than others, but the mission’s leader, Samuel Goudsmit, did not correct this belief. Now, the reason for their imprisonment at Farm Hall became clear.

After learning about Hiroshima, the scientists tried to explain what had happened. Hahn said he was glad they had not succeeded, and von Weizsäcker suggested they claim they had not wanted to build weapons. They wrote a report about their project, noting that Hahn and Strassmann discovered nuclear fission. Later, they learned about the bombing of Nagasaki, which shocked them because it showed the Allies had developed both uranium enrichment and nuclear reactor technology. Their report became the first version of a statement defending their actions after the war. Some believed Germany lost the war because its scientists were morally better, but this idea was controversial. It upset Goudsmit, whose parents were killed in Auschwitz. On 3 January 1946, six months after arriving at Farm Hall, the group was allowed to return to Germany. Hahn, Heisenberg, von Laue, and von Weizsäcker went to Göttingen, which was controlled by British forces.

On 16 November 1945, the Royal Swedish Academy of Sciences announced that Hahn had won the 1944 Nobel Prize in Chemistry for discovering nuclear fission. Hahn was still at Farm Hall when the news was shared, so the Nobel committee could not send him a telegram. Instead, he learned about the award through a newspaper on 18 November. His fellow scientists celebrated with speeches, jokes, and songs.

Hahn had been nominated for Nobel Prizes many times before discovering fission. The Nobel committee reviewed nominations for chemistry and physics separately. Although Hahn and Meitner were nominated for physics, the chemistry committee evaluated their work because nuclear research was traditionally seen as a chemistry topic. The committee received reports from scientists who praised Hahn’s work but thought Meitner and Frisch’s contributions were not as important. They also followed a rule of giving awards to the most senior scientist in a team, so Hahn was chosen alone.

Under Nazi rule, Germans could not accept Nobel Prizes after 1936, when the Peace Prize was awarded to Carl von Ossietzky. The chemistry committee’s recommendation was rejected in 1944, and the prize was delayed. After the war ended in 1945, the German boycott ended, and the committee decided to award Hahn the prize in 1944. The Academy was influenced by a scientist who argued that awarding a German scientist would show independence from the Allies, as it had done after World War I.

Hahn was asked by British and American officials to write a letter accepting the prize but said he could not attend the ceremony in December 1945 because he was still in captivity. He had six months to give a lecture and until October 1946 to collect his prize money.

Hahn was released from Farm Hall on 3 January 1946 but faced delays in traveling to Sweden. The Nobel Academy and Foundation asked the Swedish government to extend the deadline. Hahn attended the ceremony on 10 December 1946, the anniversary of Alfred Nobel’s death, where King Gustav V of Sweden presented him with the medal and diploma. Hahn gave part of his prize money to his colleague, Strassmann, who refused to use it.

The suicide of Albert Vögler in 1945 left the KWS without a leader. A British chemist, Bertie Blount, managed the organization while the Allies decided its future. He chose Max Planck, then 87 years old, as an interim president. Planck was in a town the Americans planned to hand over to the Soviets. A scientist from the Alsos Mission, Gerard Kuiper, brought Planck to Göttingen in May 1945. Planck wrote to Hahn, still in England, asking if he would become the next president. Hahn received the letter in September and agreed, though he felt he was not a good leader. After returning to Germany, he became president on 1 April 1946.

Law 25 by the Allied Control Council in 1946 limited German scientists to basic research only. On 11 July, the Allies dissolved the KWS at the request of the Americans.

Private life

In June 1911, while attending a conference in Stettin, Otto Hahn met Edith Junghans (1887–1968), a student at the Royal School of Art in Berlin. They met again in Berlin and planned to get married in November 1912. On March 22, 1913, the couple married in Stettin. Edith’s father, Paul Ferdinand Junghans, held an important position as a law officer and President of the City Parliament until his death in 1915. After their honeymoon at Punta San Vigilio on Lake Garda in Italy, they traveled to Vienna and then to Budapest, where they stayed with George de Hevesy.

They had one child, Hanno Hahn, born on April 9, 1922. Hanno joined the army in 1942 and served on the Eastern Front during World War II as a tank commander. He lost an arm during combat. After the war, he became an art historian and architectural researcher at the Hertziana in Rome. He is known for his work studying early Cistercian architecture from the 12th century. In August 1960, while traveling in France for research, Hanno died in a car accident along with his wife and assistant, Ilse Hahn (born Pletz). They left behind a 14-year-old son, Dietrich Hahn.

In 1990, the Hanno and Ilse Hahn Prize for outstanding contributions to Italian art history was created to honor Hanno and Ilse Hahn. The prize is given every two years by the Bibliotheca Hertziana – Max Planck Institute for Art History in Rome.

Death and legacy

Otto Hahn was shot in the back in October 1951 by an inventor who was angry because he felt his ideas were ignored by scientists. In 1952, Hahn was hurt in a car accident, and in 1953, he had a small heart attack. In 1962, he wrote a book titled Vom Radiothor zur Uranspaltung (From Radiothorium to Uranium Fission). The book was translated into English in 1966 and published as Otto Hahn: A Scientific Autobiography, with an introduction by Glenn Seaborg. The success of this book may have inspired Hahn to write another autobiography, Otto Hahn. Mein Leben, but he broke a bone in his neck while getting out of a car before it could be published. Over time, he became weaker and died in Göttingen on July 28, 1968. His wife, Edith, survived him for only two weeks. He was buried in the Stadtfriedhof cemetery in Göttingen. The day after his death, the Max Planck Society published an obituary notice.

Fritz Strassmann wrote:
Otto Robert Frisch recalled:
The Royal Society in London wrote in an obituary:

Hahn is known as the father of radiochemistry and nuclear chemistry. He is most famous for discovering nuclear fission, which is the basis of nuclear power and nuclear weapons. Glenn Seaborg said, "Very few people have made contributions to science and humanity as important as those made by Otto Hahn." Hahn was awarded the 1944 Nobel Prize in Chemistry for this discovery. However, some later writers have argued that Lise Meitner was not recognized because of sexism and antisemitism in the Nobel Committee. Other factors, such as conflicts between chemists and physicists, also played a role. Hahn’s efforts to improve Germany’s image after World War II have been criticized. Some say he did not take a strong political stand during the Nazi era, even though he was not a party member, and he may have shared moral responsibility for colleagues who were. In a letter to James Franck in 1946, Meitner wrote:

During his lifetime, Hahn received many honors, including orders, medals, scientific prizes, and memberships in academies and societies worldwide. In 1999, a survey by the German magazine Focus asked 500 scientists, engineers, and doctors to name the most important scientists of the 20th century. Hahn was ranked third, after Albert Einstein and Max Planck, and was considered the most important chemist of his time.

In addition to the 1944 Nobel Prize in Chemistry, Hahn was awarded:
– The Emil Fischer Medal of the Society of German Chemists (1922)
– The Cannizaro Prize of the Royal Academy of Science in Rome (1938)
– The Copernicus Prize of the University of Königsberg (1941)
– The Gothenius Medal of the Akademie der Naturforscher (1943)
– The Max Planck Medal of the German Physical Society, with Lise Meitner (1949)
– The Goethe Medal of the city of Frankfurt-on-the-Main (1949)
– The Golden Paracelsus Medal of the Swiss Chemical Society (1953)
– The Faraday Lectureship Prize with Medal from the Royal Society of Chemistry (1956)
– The Grotius Medal of the Hugo Grotius Foundation (1956)
– The Wilhelm Exner Medal of the Austrian Industry Association (1958)
– The Helmholtz Medal of the Berlin-Brandenburg Academy of Sciences and Humanities (1959)
– The Harnack Medal in Gold from the Max Planck Society (1959)

Hahn became the honorary president of the Max Planck Society in 1962.
– He was elected a Foreign Member of the Royal Society (1957).
– His honorary memberships included: the Romanian Physical Society, the Royal Spanish Society for Chemistry and Physics, the Spanish National Research Council, and academies in Allahabad, Bangalore, Berlin, Boston, Bucharest, Copenhagen, Göttingen, Halle, Helsinki, Lisbon, Madrid, Mainz, Munich, Rome, Stockholm, the Vatican, and Vienna.

He was an honorary fellow of University College London.
– He was an honorary citizen of Frankfurt am Main and Göttingen in 1959, and of Berlin in 1968.
– He was made an Officer of the Ordre National de la Légion d'Honneur of France (1959).
– He was awarded the Grand Cross First Class of the Order of Merit of the Federal Republic of Germany (1959).
– In 1966, U.S. President Lyndon B. Johnson and the U.S. Atomic Energy Commission awarded Hahn, Lise Meitner, and Fritz Strassmann the Enrico Fermi Award. The diploma for Hahn stated: "For pioneering research in naturally occurring radioactivities and extensive experimental studies culminating in the discovery of fission."
– He received honorary doctorates from the University of Göttingen, the Technische Universität Darmstadt, the Goethe University Frankfurt (1949), and the University of Cambridge (1957).

Objects named after Hahn include:
– NS Otto Hahn, the only European nuclear-powered civilian ship (1964)
– A crater on the Moon (shared with Friedrich von Hahn)
– The asteroid 19126 Ottohahn
– The Otto Hahn Prize of the German Chemical and Physical Societies and the city of Frankfurt/Main
– The Otto Hahn Medal – An Incentive for Young Scientists – and the Otto Hahn Award of the Max Planck Society
– The Otto Hahn Peace Medal in Gold of the United Nations Association of Germany (DGVN) in Berlin (1988)

At times, scientists proposed naming element 1

Publications in English

• Hahn, Otto (1936). Applied Radiochemistry. Ithaca, New York: Cornell University Press.
• Hahn, Otto (1950). New Atoms: Progress and Some Memories. New York, Amsterdam, London, Brussels: Elsevier Inc.
• Hahn, Otto (1966). Otto Hahn: A Scientific Autobiography. Translated by Ley, Willy. New York: Charles Scribner's Sons.
• Hahn, Otto (1970). My Life. Translated by Kaiser, Ernst; Wilkins, Eithne. New York: Herder and Herder.