Irène Joliot-Curie (1897-1956), with husband Frédéric, studied artificial radioactivity and contributed to the discovery of the neutron. They won a Nobel Prize for chemistry.
Irène Joliot-Curie, elder daughter of famed scientists Marie and Pierre Curie, won a Nobel Prize in chemistry in 1935 for the discovery, with her husband Frédéric Joliot-Curie, of artificial radioactivity . She began her scientific career as a research assistant at the Radium Institute in Paris, an institute founded by her parents, and soon succeeded her mother as its research director. It was at the Institute where she met her husband and lifelong collaborator, Frédéric Joliot. They usually published their findings under the combined form of their last names, Joliot-Curie.
Born on September 12, 1897, in Paris to Nobel laureates Marie and Pierre Curie, Irène Curie had a rather extraordinary childhood, growing up in the company of brilliant scientists. Her mother, the former Marie Sklodowska and her father, Pierre Curie, had been married in 1895 and had become dedicated physicists, experimenting with radioactivity in their laboratory. Marie Curie was on the threshold of discovering radium when little Irène, or "my little Queen" as her mother called her, was only a few months old. As Irène grew into a precocious, yet shy child, she was very possessive of her mother who was often preoccupied with her experiments. If, after a long day at the laboratory, the little Queen greeted her exhausted mother with demands for fruit, Marie Curie would turn right around and walk to the market to get her daughter fruit. Upon her father Pierre Curie's untimely accidental death in 1908, Irène was then more influenced by her paternal grandfather, Eugene Curie. It was her grandfather who taught young Irène botany and natural history as they spent summers in the country. The elder Curie was also somewhat of a political radical and atheist, and it was he who helped shape Irène's leftist sentiment and disdain for organized religion.
Curie's education was quite remarkable. Marie Curie made sure Irène and her younger sister, Eve Denise (born in 1904), did their physical as well as mental exercises each day. The girls had a governess for a time, but because Madame Curie was not satisfied with the available schools, she organized a teaching cooperative in which children of the professors from Paris' famed Sorbonne came to the laboratory for their lessons. Madame Curie taught physics, and other of her famous colleagues taught math, chemistry, language and sculpture. Soon Irène became the star pupil as she excelled in physics and chemistry. After only two years, however, when Irène was 14, the cooperative folded and Irène enrolled in a private school, the College Sevigne, and soon earned her degree. Summers were spent at the beach or in the mountains, sometimes in the company of such notables as Albert Einstein and his son. Irène then enrolled at the Sorbonne to study for a diploma in nursing.
During World War I, Madame Curie went to the front where she used new X-ray equipment to treat soldiers. Irène soon trained to use the same equipment and worked with her mother and later on her own. Irène, who was shy and rather antisocial in nature, grew to be calm and steadfast in the face of danger. At age 21, she became her mother's assistant at the Radium Institute. She also became quite adept at using the Wilson cloud chamber, a device which makes otherwise invisible atomic particles visible by the trails of water droplets left in their wake.
In the early 1920s, after a jubilant tour of the United States with her mother and sister, Irène Curie began to make her mark in the laboratory. Working with Fernand Holweck, chief of staff at the Institute, she performed several experiments on radium resulting in her first paper in 1921. By 1925 she completed her doctoral thesis on the emission of alpha rays from polonium, an element that her parents had discovered. Many colleagues in the lab, including her future husband, thought her to be much like her father in her almost instinctive ability to use laboratory instruments. Frédéric was several years younger than Irène and untrained in the use of the equipment. When she was called upon to teach him about radioactivity, Irène started out in a rather brusque manner, but soon the two began taking long country walks. They married in 1926 and decided to use the combined name Joliot-Curie to honor her notable scientific heritage.
After their marriage, Irène and Frédéric Joliot-Curie began doing their research together, signing all their scientific papers jointly even after Irène was named chief of the laboratory in 1932. After reading about the experiments of German scientists Walther Bothe and Hans Becker, their attention focused on nuclear physics, a field yet in its infancy. Only at the turn of the century had scientists discovered that atoms contain a central core or nucleus made up of positively charged particles called protons. Outside the nucleus are negatively charged particles called electrons. Irène's parents had done their work on radioactivity, a phenomenon which occurs when the nuclei of certain elements release particles or emit energy. Some emissions are called alpha particles which are relatively large particles resembling the nucleus of a helium atom and thus contain two positive charges. In their Nobel Prize-winning work, the elder Curies had discovered that some elements, the radioactive elements, emit particles on a regular, predictable basis.
Irène Joliot-Curie had in her laboratory one of the largest supplies of radioactive materials in the world, namely polonium, a radioactive element discovered by her parents. The polonium emitted alpha particles which Irène and Frédéric used to bombard different elements. In 1933 they used alpha particles to bombard aluminum nuclei. What they produced was radioactive phosphorus. Aluminum usually has 13 protons in its nuclei, but when bombarded with alpha particles which contain two positive charges each, the protons were added to the nucleus, forming a nucleus of phosphorus, the element with 15 protons. The phosphorus produced is different from naturally-occurring phosphorus because it is radioactive and is known as a radioactive isotope.
The two researchers used their alpha bombardment technique on other elements, finding that when a nucleus of a particular element combined with an alpha particle, it would transform that element into another, radioactive element with a higher number of protons in its nucleus. What Irène and Frédéric Joliot-Curie had done was to create artificial radioactivity. They announced this breakthrough to the Academy of Sciences in January of 1934.
The Joliot-Curies' discovery was of great significance not only for its pure science, but for its many applications. Since the 1930s many more radioactive isotopes have been produced and used as radioactive trace elements in medical diagnoses as well as in countless experiments. The success of the technique encouraged other scientists to experiment with the releasing the power of the nucleus.
It was a bittersweet time for Irène Joliot-Curie. An overjoyed but ailing Marie Curie knew that her daughter was headed for great recognition but died in July of that year from leukemia caused by the many years of radiation exposure. Several months later the Joliot-Curies were informed of the Nobel Prize. Although they were nuclear physicists, the pair received an award in chemistry because of their discovery's impact in that area.
After winning the Nobel Prize, Irène and Frédéric were the recipients of many honorary degrees and named officers of the Legion of Honor. But all these accolades made little impact on Irène who preferred spending her free time reading poetry or swimming, sailing, skiing or hiking. As her children Helene and Pierre grew, she became more interested in social movements and politics. An atheist and political leftist, Irène also took up the cause of woman's suffrage. She served as undersecretary of state in Leon Blum's Popular Front government in 1936 and then was elected professor at the Sorbonne in 1937.
Continuing her work in physics during the late 1930s, Irène Joliot-Curie experimented with bombarding uranium nuclei with neutrons. With her collaborator Pavle Savitch, she showed that uranium could be broken down into other radioactive elements. Her seminal experiment paved the way for another physicist, Otto Hahn, to prove that uranium bombarded with neutrons can be made to split into two atoms of comparable mass. This phenomenon, named fission, is the foundation for the practical applications of nuclear energy—the generation of nuclear power and the atom bomb.
During the early part of World War II, Irène continued her research in Paris although her husband Frédéric had gone underground. They were both part of the French Resistance movement and by 1944, Irène and her children fled France for Switzerland. After the war she was appointed director of the Radium Institute and was also a commissioner for the French atomic energy project. She put in long days in the laboratory and continued to lecture and present papers on radioactivity although her health was slowly deteriorating. Her husband Frédéric, a member of the Communist Party since 1942, was removed from his post as head of the French Atomic Energy Commission in 1950. After that time, the two became outspoken on the use of nuclear energy for the cause of peace. Irène was a member of the World Peace Council and made several trips to the Soviet Union. It was the height of the Cold War and because of her politics, Irène was shunned by the American Chemical Society when she applied for membership in 1954. Her final contribution to physics came as she helped plan a large particle accelerator and laboratory at Orsay, south of Paris in 1955. Her health worsened and on March 17, 1956, Irène Joliot-Curie died as her mother had before her, of leukemia resulting from a lifetime of exposure to radiation.
Further Reading on Irène Joliot-Curie
Opfell, Olga S., The Lady Laureates: Women Who Have Won the Nobel Prize, Scarecrow, 1978.
Pflaum, Rosalynd, Grand Obsession: Madame Curie and Her World, Doubleday, 1989.