Irène Joliot-Curie and Artificial Radioactivity


When Marie and Pierre Curie discovered the natural radioactive elements polonium and radium, they did something truly remarkable– they uncovered an entirely new property of matter. The Curies’ work was the key to unlocking the mysteries of the atom, which was previously thought to be indivisible. Their research opened the door to nuclear medicine and clean energy, and it also led to the development of nuclear weapons.

Irène Joliot-Curie, her husband Frédéric, and many of their contemporaries were completely against the use of nuclear science as a weapon. They risked their lives to guard their work from governments hell-bent on destruction, and most of them, Irène included, ultimately sacrificed their health and longevity for the good of society.


Irène and her mother work in the lab. Source: Wikimedia

Childhood

Irène Curie was born September 12th, 1897 in Paris to Marie and Pierre Curie. She was a shy, serious child and quite attached to her mother. Irène idolized Marie from the start and spent her life trying to get closer to her. But the Curies spent long hours working in the lab. Once they won the Nobel Prize for discovering radium, Irene saw her mother even less.

Marie Curie was wary of the French educational system, which discouraged free thought in favor of rote memorization. So she and a few other parents formed a collective educational commune and took turns teaching each other’s children a diverse array of subjects from Chinese to sculpture. After a few years, the collective disbanded and Irène enrolled in a private school in Paris.

When Irène was eight years old, her father was trampled by the horses of a stagecoach and died instantly. Marie was so consumed by grief that she would avoid or abruptly end any conversation about Pierre, which frustrated Irène and further alienated her from her mother. Whenever they weren’t in school, Marie sent Irène and her younger sister Eve to stay with their aunt in a cottage by the sea while she worked in the lab and picked up the pieces of her life.


Irène and Marie worked together as nurses during WWI. Source: IEEE

Futuristic Florence Nightingale

World War I erupted when Irène was seventeen. After a few months, she was finally reunited with her mother.

Marie threw herself into the war effort. She built a fleet of 20 mobile x-ray labs using donated vehicles, and powered the equipment with dynamos that ran off the cars’ engines. Irène took a nursing course and helped Marie teach doctors and nurses how to take x-rays of wounded soldiers. Many were skeptical of the technology until they saw for themselves how useful it could be to spot bone fractures and facilitate easy removal of bullets and shrapnel.

Irène traveled with her mother for two years before going back to school. She wasted no time, earning three degrees with distinction in just two years at the Faculty of Science in Sarbonne. Whenever she had time, she’d go back to the battlefield to help x-ray soldiers. Over the course of the war, it is estimated that more than one million soldiers received x-ray examinations thanks to the Curie women.

Lab Partners for Life


Irène and Frédéric work in the lab at the Radium Institute. Source: Encyclopədia Brittanica

Irène became her mother’s assistant at the Radium Institute after the war. Here, she meets the friendly and outgoing Frédéric Joliot, chemical engineer in the making.

Marie hired him to work in the lab and assigned Irène to teach him the ropes of radioactive materials. They soon discovered a shared love of science, sports, and anti-war politics, and they were married a year later.

The 1930s is widely considered to be the golden age of physics. In a way, it’s the original global open source movement. Research teams all over the world were making new discoveries about the stuff of matter and its inner workings, and publishing their findings before the slides had dried in the rack. Not everyone was keen to share their methods, though. Irène had a bit of a professional rivalry with Lise Meitner, a physicist who discovered nuclear fission along with Otto Hahn.

Irène and Frédéric worked well together at the Institute which was one of the finest labs in the world. Both had education and experience in both physics and chemistry, and their differing approaches to problem solving were perfect complements. But success did not come quickly to the Joliot-Curies. It wasn’t for lack of research, though—they just didn’t interpret their data correctly.


A cloud chamber image of the first positron. Source: Wikimedia

Neutrons, Positrons, and Perseverance

A few years prior, a pair of German physicists had bombarded beryllium with polonium particles and produced powerful radiation. The Joliot-Curies repeated the experiment and then carried it further by firing polonium at other substances. When the particles left a chunk of paraffin wax at one-tenth the speed of sound, they knew they were on to something, but what? They believed they had seen gamma rays, and published an article outlining their findings.

Physicist Ernest Rutherford, whose gold foil experiments changed our understanding of atomic structure, wasn’t convinced. He argued that since gamma rays have no mass, it would be impossible for them to move heavy polonium particles so fast. He told his colleague, James Chadwick, to repeat the experiment. After ten days of work and sleepless nights, Chadwick concluded that the Joliot-Curies’ data conclusively proved the existence of the neutron, which Rutherford had proposed twelve years earlier. Chadwick snagged the 1935 Nobel Prize in Physics for this discovery, and the Joliot-Curies had to go skulking back to the drawing board.

Now the race was really on. The discovery of the neutron was a great boon to physics and allowed scientists to peer inside the nucleus. The Joliot-Curies used a Wilson cloud chamber to conduct experiments with polonium and saw tiny particles behaving strangely. Again, they published their findings without really understanding what they had seen. When American physicist Carl David Anderson repeated their experiments, he concluded that the Joliot-Curies had witnessed the positron in action. Again, the Joliot-Curies watched the Nobel Prize go to someone else for work they had done.


Irène and Frédéric immersed in scientific thought. Source: Mental Floss

Eureka!

Irène and Frédéric kept searching for positrons by exposing different elements to polonium. One night, Frédéric repeated the experiment he and Irene had done using the Wilson cloud chamber, a chunk of polonium, and a sheet of aluminium foil. He had a Geiger counter nearby to measure radioactivity. When he was finished, he took the polonium away, but something strange happened. The Geiger counter kept clicking, sensing radioactivity. It was coming from the aluminium foil, which had absorbed alpha particles from the polonium and become artificially radioactive.

Frédéric ran from his downstairs lab to get Irene. He ran the experiment again without telling her what he was doing. Sure enough, the Geiger counter kept clicking after he took the polonium away and continued for several minutes. The foil had absorbed alpha particles from the polonium and become a temporarily radioactive form of phosphorus. After a few minutes, it decayed into silicon. There was no misinterpreting the data this time. The Joliot-Curies knew exactly what they’d done. They’d discovered artificial radioactivity, and cemented their place in history.


Irène and Frédéric at the 1935 Nobel Prize ceremony. Source: Atomic Heritage

Nobels and Nobility

The Joliot-Curies won the Nobel Prize in Chemistry the following year, in 1935. By this time, the dangers of radioactive materials weren’t yet fully understood, but radiation poisoning had already taken many lives.

Of course, the power of nuclear science is two-sided coin. Radiation kills cancer, but it also causes cancer. Artificial radioactivity on a grand scale can create clean energy for all, but it can also decimate cities. Irene and Frédéric just wanted to build a reactor.

The Joliot-Curies had always been eager to share their work with the world, but when France went to war with Germany, they decided to reel it in. In 1939, they sealed their nuclear fission research in a vault at the French Academy of Sciences, where it stayed until 1949.

A year after Irène and Frédéric were married, doctors told Irène she had tuberculosis. This diagnosis hardly slowed her down throughout her life, though her condition was aggravated her work habits and by food shortages during the war. She continued to work in the lab and installed a cot so she could take breaks to rest. By the 1950s, Irène spent much of her time convalescing in the Alps. In January 1956, she was diagnosed with leukemia and died a few months later at age 58.

Irène Joliot-Curie’s story may be overshadowed by her famous parents, but her work provided the vital link between their work and the development of nuclear medicine. She deserves to be lauded for her undeniable contributions to science.



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