The news of the bombing of Hiroshima and Nagasaki caused such a shock in Otto Hahn, the discoverer of uranium fission, that his friends had to be on duty around the clock for fear of suicide.
Otto Hahn was born on March 8, 1879 in Frankfurt-Main. His father was a craftsman, then became the owner of a small factory and a deputy of the city council. The family did not live in poverty, but of the four sons, only the eldest, Karl, was able to send to the gymnasium. The three youngest and the youngest, Otto, went to a vocational school.
As a teenager, Gan became interested in spiritualism. But after reading many occult writings, he became convinced of their meaninglessness and never returned to them. Maybe it was then that he developed a deep distrust of any kind of speculative knowledge that defies objective verification. Throughout his life, Gan remained indifferent to metaphysical and religious issues.
His true interests were determined late. Lively, inventive for pranks, Otto thought little about choosing a profession. He decided to become a chemist only in his senior class, under the influence of the lectures of the then famous researcher M. Freund.
In 1897, Hahn entered the University of Marburg, in 1901 he defended his thesis in organic chemistry. The university was followed by military service, for which Otto did not show the slightest zeal. Soon after the service, the management of one of the factories decides to hire a well-trained, well-mannered young man to work abroad. In 1904, Hahn went to London, intending at the same time to study chemistry with V. Ramsay.
Ramsay at that time was studying radioactive elements and instructed Otto to get a strong preparation of radium from barium salt. The outcome of the experiment predetermined all further activities of Ghana. The fledgling novice, unexpectedly for himself and his colleagues, discovered a new radioactive substance, which he called radiotorium. When six months later his stay in London ended, Ramsay suggested that Ghan give up work in industry and devote himself entirely to a new, little-known field - radiochemistry. Thus, a new period began in the life of Otto Hahn, who was still drifting with the flow. Deep down, considering himself self-taught, he decided to undergo an internship with the leading researcher in the field of radioactivity E. Rutherford before returning to Berlin. Otto's relationship with science has always been free of self-interest. Moreover, in those years he worked for Rutherford for free: there were no rates, and then the trainees were not entitled to a scholarship. He received his first full-time position at the age of 33. Before that, his parents and brothers supported him, they also paid for the costs of the experiments.
Rutherford received Ghana amicably, but stated that he did not believe in the existence of radiotorium. In response, Otto conducted similar experiments with other substances that emit alpha particles, and discovered another substance - thorium C, then radioactinium. In Montreal, near Rutherford, Hahn finally established himself in the decision to devote himself to research into radioactivity. And the point is not so much that here he got acquainted with physical problems and methods, as in communication with Rutherford. The brilliant, democratic and often noisy Rutherford, not in the least like the dignified German professors, became Otto's ideal. And the laboratory environment, seriousness in work, free discussion, independence of judgment and open admission of mistakes became a model for the young scientist to achieve which he later aspired to at his institute.
Returning to Berlin in 1906, Hahn entered the chemical laboratory of the University of Berlin under the supervision of Professor Z. Fischer. An old organic chemist, Fischer considered the most reliable instrument of a researcher "his own nose", and not a counter registering mysterious rays. On the other hand, Hahn quickly became friends with a circle of young Berlin physicists. Here on September 28, 1907, he, an inventive chemist, met the theoretical physicist Lise Meitner. Since that time, they have worked together for three decades. The Hahn-Meitner combination has become one of the most successful and fruitful in atomic research.
Otto Hahn and Lise Meitner
In 1912, Hahn transferred to the newly founded Institute of Chemistry of the Kaiser Wilhelm Society (later Hahn became the director of this institute). Otto's track record over the years is impressive. In 1907, a new element was discovered - mesotorium. In 1909, important experiments were carried out to study the phenomena of recoil. In 1913, with the participation of Meitner, he discovered uranium X2. Despite the brilliant work, the old and cramped wooden workshop building served as the room for the laboratory. And the path to an academic career for Ghana was closed for a long time. Although he was promoted to professor in 1910, until 1919 radiochemistry was not among the subjects taught at German universities.
In August 1914, Ghana was drafted into the army. At that time, the need to fight did not cause discord with his conscience. Probably, it was influenced by the surge of nationalistic and loyalist sentiments, home education, which elevated to absolute the strict fulfillment of duty to the Kaiser and the nation, and possibly the romantic idea of war. In the first months of the war, in Ghana, the carelessness of the student years seemed to wake up, especially since its part did not take a direct part in the hostilities. At the beginning of 1915, he was asked to start developing poisonous substances, and after short hesitation, he agreed, believed in the arguments about the humanity of the new weapon, which, allegedly, would bring the end of the war closer. Most of his colleagues did the same. (True, not all: the German chemist, 1915 Nobel laureate R. Willstatter, for example, refused.) Only later Otto remarked with pain: “In essence, what we were doing then was terrible. But that was."
As you can see, Otto and colleagues did not reproach him, who regarded his creative life as a chain of brilliant successes, a continuous ascent to the truth. Hahn's career, according to M. von Laue (German physicist, Nobel Prize laureate), can be "likened to a curve that, starting from a high point - with the discovery of the radiatorium, rises higher and higher - towards the discovery of the mesotorium, reaches its maximum at the moment of the discovery of nuclear fission uranium ".
Similar experiments were carried out in Paris by Irene Curie.
Hahn, Meitner and a young employee Strassmann studied several radioactive isotopes that were obtained by bombarding uranium or thorium with neutrons, and so improved the experimental methodology that in just a few minutes they could isolate the desired radioactive isotope. Organized competitions. Meitner held a stopwatch in her hand, while Hahn and Strassmann took the irradiated preparation, dissolved, precipitated, filtered, separated the precipitate and transferred it to the counter. In less than two minutes, they did what would normally take two to three hours. Everything that was created in the laboratory of Hahn was considered by the atomic lobbyists of the world to be an indisputable truth, they used the terminology of Hahn (by the way, borrowed from the works of D. Mendeleev). Research in the three largest laboratories in the world - in Berlin, Rome (Fermi) and Paris - seemed to leave no doubt that when uranium is irradiated with neutrons, the decay products contain ek-rhenium and eka-osmium. It was necessary to decipher the paths of their transformations, to determine the half-lives. These elements were considered transuranic. True, in 1938, Irene Curie discovered an isotope similar to lanthanum in the decay products, but she did not have enough confidence in this, and in fact she was on the verge of discovering uranium fission - such a decay that seemed impossible. The energy that bound protons and neutrons in the nucleus of an atom was so great that it seemed inconceivable to imagine that only one neutron could overcome it.
What were these processes really like? They were sorted out a little later, but for now, political issues have come to the fore. Neutrons and protons had to be forgotten for a while, military marches and warlike speeches did not bode well. Jewish woman Lisa Meitner, an Austrian citizen, was denied a passport by the German authorities after the Anschluss. According to Nazi law, she also had no right to leave Germany. The only way out for her was flight. Hahn asked Niels Bohr for help. The Dutch government agreed to accept her without a passport. Lise packed the most necessary things and left for Holland "on vacation".
Concern and anxiety in connection with Meitner's departure consumed Otto for almost the entire summer of 1938. Autumn has come. That autumn when Hahn and Strassmann made the most important discovery. Experiments and theoretical searches resumed. The absence of Meitner was acutely felt: there was a lack of a reasonable advisor and a strict judge, a theoretician who would carry out complex calculations.
Fritz Strassmann
Hahn resorted to the indicator method. A variety of radioactive tracers were used many times, but the result was the same. The radioactive substance that appeared when uranium was bombarded with slow neutrons resembled barium in properties; it could not be separated from barium by any chemical method. So Otto Hahn and Fritz Strassmann actually discovered the fission of uranium nuclei. Strassmann was 37 at the time, and Hahn was preparing to celebrate his sixtieth birthday.
The article was published at the end of 1938. At the same time, Hahn sent the results of the experiments to Meitner, awaiting her evaluation. The new year brought a new theory. According to her, the uranium nucleus when irradiated with slow neutrons should split into two parts, into atoms of barium and krypton. In this case, repulsive forces appear between the newly formed nuclei, the energy of which reaches two hundred million electron-volts. This is a colossal energy that cannot be obtained in other processes. Physics borrowed the term "fission" from biology, this is how protozoa reproduce. A colleague and nephew of Meitner Frisch, urgently conducting an experiment on the fission of uranium, confirmed the theory and undertook to write an article.
The results obtained by Hahn and Strassmann were so sharply at odds with the opinions of the most authoritative scientists that they puzzled the researchers themselves. Hahn's letters to Meitner now and then flashed the words "amazing," "supremely amazing," "stunning," "fantastic result." To draw the correct conclusion, which runs counter to the ideas of the time, Otto required not only perspicacity, but also extraordinary courage. They gave Ghana confidence in the purity of the experiment, i.e. in the reliability of the results obtained.
The events of just a few days, which took place in the largest scientific centers of the United States of America, may well serve as a scenario for an exciting adventure film.
Unaware that the discovery of Hahn, Strassmann and Meitner must be kept secret, Bora Rosenfeld's closest associate arrives in Princeton (USA) and finds himself at a physicists' party at the university club. He is bombarded with questions: what's new in Europe? Rosenfeld talks about the experiments of Hahn and Strassmann and the theoretical conclusions of Meitner and Frisch. A Fermi employee is present at the meeting; that night he drives to New York, breaks into Fermi's office and breaks the news. Within minutes Fermi began developing a project for upcoming experiments. First, you need to reproduce the process of fission of a uranium nucleus, then measure the released energy. Fermi realizes what he missed five years ago when he first bombarded uranium with slow neutrons.
Enrico Fermi
In the underground of Columbia University, a uranium nucleus is fissioned, unaware that Frisch has already conducted a similar experiment. Hastily (in a hurry to stake out someone else's discovery) a message is being prepared for the journal "Nature".
Upon learning of the information leak, Bohr worries that someone will outrun Meitner and Frisch. Then they will find themselves in the position of appropriating someone else's discovery. At the convention in Washington, Bohr learns that Fermi's uranium fission experiments are in full swing, and sends telegrams to Copenhagen to Frisch to immediately publish the results of the experiments. The next day, a fresh issue of the magazine appeared with an article by Hahn and Strassmann. On the same day, consoling news arrived - Frisch sent the article to the press. Now Bor is calm and can tell everyone about uranium fission. Even before he finished his speech, several people left the hall and almost ran to the Carnegie Institute, to the powerful accelerator. It was necessary to immediately change targets and investigate the fission of the uranium nucleus.
The next day, Bohr and Rosenfeld were invited to the Carnegie Institution. For the first time Bohr saw the division process on the oscilloscope screen.
At the same time in Paris, the Joliot-Curies observed the decay of uranium and thorium nuclei, calling this decay an "explosion". Frederick's article appeared just two weeks after Meitner and Frisch's article. Thus, in less than a month, four laboratories (in Copenhagen, New York, Washington, and Paris) fissioned a uranium nucleus and showed that enormous energy is released. But few people knew that there was also a fifth laboratory - at the Polytechnic Institute in Leningrad, where the theory of uranium fission was also developed.
References:
1. Gernek F. Pioneers of the Atomic Age. M.: Progress, 1974. S. 324-331.
2. Konstantinova S. Splitting. // Inventor and innovator. 1993. No. 10. S. 18-20.
3. Temples Yu Physics. Biographical reference book. M.: Science. 1983. S. 74.
