Frédéric Joliot and Irène Joliot-Curie used alpha particles from polonium to bombard aluminum and create phosphorus 30, an artificial nucleus that is radioactive.

In 1930, a German team of scientists reported that beryllium bombarded by alpha particles emitted a new sort of penetrating radiation. In France, the husband-wife team of Irène Joliot-Curie and Frédéric Joliot confirmed the German results and in the process came close to proving the existence of the neutron, of which the new radiation was composed. This particle, which has no charge but has the same mass as the proton, joins the proton to form the nucleus of the atom. Atomic nucleus British physicist James Chadwick Chadwick, James won a Nobel Prize in Physics for making the actual discovery of the neutron. Nobel Prize recipients;James Chadwick[Chadwick]
[kw]First Artificial Radioactive Element Is Developed (1933-1934)
[kw]Artificial Radioactive Element Is Developed, First (1933-1934)
[kw]Radioactive Element Is Developed, First Artificial (1933-1934)
[kw]Element Is Developed, First Artificial Radioactive (1933-1934)
Radioactivity
Phosphorus 30
Elements;radioactive
[g]France;1933-1934: First Artificial Radioactive Element Is Developed[08220]
[c]Science and technology;1933-1934: First Artificial Radioactive Element Is Developed[08220]
[c]Physics;1933-1934: First Artificial Radioactive Element Is Developed[08220]
Joliot-Curie, Irène
Joliot, Frédéric

In 1932, the Joliot-Curies, studying cosmic radiation in the high Alps, observed the positron, Positrons a particle with the same mass as the electron but with a positive rather than a negative charge. They failed to follow up their observation, and that same year, an American physicist, Carl David Anderson, Anderson, Carl David identified the positron, using equipment similar to that used by the Joliot-Curies.

By early 1933, the Joliot-Curies were using alpha particles produced from polonium to bombard boron, beryllium, fluorine, aluminum, and sodium. After the bombardment, these elements emitted neutrons and both positrons and electrons. The accuracy of the results of their experiments was questioned at the Seventh Solvay Conference, which was attended by most of the major physicists in Europe. They returned to Paris with damaged pride and a new determination to prove conclusively that neutrons and positrons were emitted at the same time from their irradiated targets.

To conduct the necessary experiments, they were forced to modify their experimental apparatus. Until now, the Geiger counter, which detected radioactivity, had been automatically turned off when the radioactive source (the source of the alpha particles) was removed. In the new arrangement, it would be left on after the source was removed. With this arrangement, they noticed that aluminum continued to emit positrons for some time after the removal of the radioactive source. This meant that the aluminum target had been made artificially radioactive by bombardment with alpha particles.

The Joliot-Curies were certain that they had produced artificial radioactivity. In order to place their discovery beyond doubt, they needed to separate chemically the source of the new radioactivity and to demonstrate that it had nothing to do with the original aluminum target. On January 15, 1934, friends, including Irène’s famous mother, Marie Curie, Curie, Marie received frantic telephone calls from the young researchers and rushed to the laboratory. From makeshift apparatus scattered in apparent disarray over several tables, the Joliot-Curies bombarded aluminum with alpha particles and separated from the irradiated samples an isotope of phosphorus with a half-life of only three minutes and fifteen seconds. Marie Curie, who was dying of the leukemia produced by her lifetime work with radioactivity, was handed a tiny tube containing the first sample of artificially produced radioactivity. Her face expressed joy and excitement. Other colleagues filled the room with lively discussions.

The Joliot-Curies soon repeated their experiments with boron and magnesium, producing still other sources of artificial radioactivity. They promptly sent off a report of their discovery to the scientific press. Its publication opened a floodgate of new experiments on the transmutation of nuclei, which led directly to the discovery of “nuclear fission” five years later.

The report of the discovery of artificial radioactivity was published early in 1934, and in 1935 the discovery earned for the husband and wife a shared Nobel Prize in Chemistry. Nobel Prize recipients;Irène Joliot-Curie[Joliot Curie]
Nobel Prize recipients;Frédéric Joliot[Joliot] The scientific community almost immediately recognized the discovery as equal to that of the neutron or the positron. Physicist Enrico Fermi and his group in Rome quickly noted that neutrons were more effective in producing artificial radioactivity than the alpha particles used in the original experiments. The entire community, including the Joliot-Curies, began to study artificial radioactivity produced by bombarding different elements with neutrons. Studies on uranium in Rome, Berlin, and Paris led to confusing results, which were finally interpreted as nuclear fission Nuclear fission in 1939. (Nuclear fission is the splitting of an atomic nucleus into two parts, especially when bombarded by a neutron. When the nuclei of uranium atoms are split, great amounts of energy are released.) Radioactivity
Phosphorus 30
Elements;radioactive

• Biquard, Pierre. Frédéric Joliot-Curie: The Man and His Theories. Translated by Geoffrey Strachan. New York: Paul S. Eriksson, 1966. Biography by a scientific colleague who was an eyewitness to the discovery of artificial radioactivity. Marred somewhat by the author’s extremely sentimental attachment to Frédéric Joliot.
• Goldsmith, Maurice. Frédéric Joliot-Curie. London: Lawrence & Wishart, 1976. Readable biography written by a colleague of Joliot provides a clear account of the physics of the scientist’s work but tends to idealize him. Includes discussion of Joliot’s role in World War II that reads like a spy novel.
• Jungk, Robert. Brighter than a Thousand Suns: A Personal History of the Atomic Scientists. Translated by James Cleugh. New York: Harcourt Brace, 1958. History of the Manhattan Project provides solid background on the physics of that time. Chapter titled “An Unexpected Discovery” provides a history of the discovery of artificial radioactivity in the context of the time during which it was made.
• Opfell, Olga S. “Irène Joliot-Curie.” In The Lady Laureates: Women Who Have Won the Nobel Prize. 2d ed. Metuchen, N.J.: Scarecrow Press, 1986. Readable account of the vital role Joliot-Curie played in the discovery of artificial radioactivity. Emphasizes her life as a wife and mother and as the daughter of a Nobel laureate.
• Rayner-Canham, Marelene F., and Geoffrey W. Rayner-Canham. A Devotion to Their Science: Pioneer Women of Radioactivity. Philadelphia: Chemical Heritage Foundation, 2005. Collection of biographical essays on twenty-three women involved in atomic science research in the early part of the twentieth century includes essays on Irène Joliot-Curie and Marie Curie as well as on many lesser-known scientists whose stories are rarely told.
• Rhodes, Richard. The Making of the Atomic Bomb. New York: Simon & Schuster, 1986. Excellent history of early twentieth century physics. Chapter titled “Stirring and Digging” provides a lively description of the discovery of artificial radioactivity set in the context of the physics community and the political events surrounding it.

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