Remembering Irene Curie

Irene Curie inaugurating the Institute of Nuclear Physics. Besides him are Kailas Nath Katju and A.P. Patro (Photo from the archive of SINP)

 

 It was January 11, 1950. A lady walked up the stairs of the new building inside the Rajabazar campus of the University of Calcutta. She entered the auditorium on the first floor to a thunderous applause. She was only the second woman to receive the Nobel Prize in science. Her field of research was nuclear science, and aptly enough, she had been invited to inaugurate the new building of the Institute of Nuclear Physics of the University by Meghnad Saha, the founder of the Institute. Since then, every year the Institute celebrates January 11 as its foundation day. A few months later, the Institute became an independent institution outside the control of the University of Calcutta. In 1956, it was renamed the Saha Institute of Nuclear Physics after the death of Saha.

 
 The lady was Irene Curie, the elder daughter of the illustrious couple, Mary and Pierre Curie, the first husband and wife team to be awarded the Nobel Prize. Mary, of course, was the first woman to receive the coveted prize and to date the only woman to win it twice. Following the footsteps of such parents is not an easy task. The spotlight of publicity was on her all the time; even her receiving the doctorate became a news item in the New York Times in distant America. It was to her credit that such media attention could not distract her from pursuing the first love of her life, science. 
 Irene was born exactly one hundred and twenty five years ago, on September 12, 1897. Her mother noted down the development of her child, interposed by records on her research. Thus, a note on Irene’s fifteenth tooth by the proud mother was followed by the announcement of the discovery of a new element, radium. Irene had a chequered childhood. Pierre died in an accident in 1906 when Irene was only nine years old. Madame Curie, as Mary was universally known, was devastated by the sudden bereavement, yet she had to bring up her two daughters and continue the research. 
 Madame Curie was fortunate that Pierre’s father, Eugène Curie, came forward to assist her in looking after Irene and her sister, Eve, till his death in 1910. Eugène Curie was a physician with a progressive outlook. He had participated in the Paris Commune uprising in 1971, tending to the injuries of the defenders of the Commune. The Commune had failed, but it left a deep impression on Eugène, which shaped the views of his son and granddaughters. Irene learned to love nature and poetry from her grandfather. Mary was a very secular and progressive social thinker. Irene was also anticlerical and liberal socialist in her views, yet it was Eugène who had shaped her character. To quote Irene, “My spirit had been formed in great part by my grandfather, Eugène, and my reactions to political or religious questions came from him more than from my mother.” The young Irene displayed a great strength of character, standing by her mother, when she went into a depression following the vilification campaign launched against her for the ‘audacity’ of a woman to stand for membership in the French Academy of Sciences in 1912. Mary was defeated in the election, but coincidentally, later that year, she won her second Nobel Prize, the first person in history to do so. Irene never forgot the incident. When she was a reputed scientist, she applied for membership of the Academy three times, knowing fully well that it would be denied, highlighting the misogynist character of the scientific establishment. 
 Irene entered school at the age of twelve. It was not an ordinary school. Called the Co-operative, it was established by a number of leading French scientists for their children. The curriculum included not only the usual subjects but also such diverse topics as Chinese language and sculpture. Classes were held in the houses of the students, and teachers included two Nobel Laureates, Mary and Jean Perrin. Two years later, Irene enrolled in an ordinary school and later went to the University of Paris, Sorbonne. However, her study was interrupted by the First World War, when her mother set up a number of mobile X-ray units for treating the wounded soldiers. Mary personally went to the battlefields, accompanied by Irene, who first served as a nurse, and later found herself lecturing to the physicians, who were much older than her, about X-ray photographic technique. 
 She graduated from the Sorbonne in 1918 and joined the Radium Institute, established by her mother. In 1925, she earned her doctorate degree for her work on alpha decay of polonium, an element discovered by her parents. Her supervisor was Paul Langevin, a brilliant physicist. By this time, she had met Frédéric Joliot, whom she was instructing on radioactivity. She found in him a kindred soul, and they married next year. It was one of the happy marriages where both the husband and the wife complemented each other in all walks of life. Interestingly, Irene, a doctorate in physics, was counted among the greatest radiochemists of the world, while Frédéric, a chemist by training, looked after the physics side. They often signed their names as Joliot-Curie.
 It is not possible to discuss all the achievements of Irene and Frédéric within a short article. We will restrict ourselves to a few cases where they came very close to epoch-making discoveries but stumbled at the last step. However, in science, sometimes failures are almost as important as successes; accounts of their experiments helped others to the final discovery. We will also describe briefly their triumph, which led to a Nobel Prize for the duo, and how that discovery has impacted modern life. 
 Ernest Rutherford, the discoverer of the nucleus, had predicted the existence of the neutron, a neutral constituent of the nucleus, in 1920. Ten years later, the Joliot-Curies found that bombardment of beryllium by alpha particles from polonium results in the emission of some uncharged radiation which can knock out a proton from a block of paraffin. They identified the radiation as gamma-rays of very high energy. Rutherford, learning of the discovery, commented, “I don’t believe it.” His student, James Chadwick, repeated the experiment and correctly identified the new radiation as neutrons. He won the Nobel Prize for his discovery in 1935. Earlier, Irene and Frédéric had seen the track of a positively charged particle in their cloud chamber photographs but had misidentified it as that of a proton. Later in 1932, Carl Anderson saw a similar track in his setup and established that it was due to a positron, the antiparticle of the electron predicted some years back by Paul Dirac. Anderson won the Nobel Prize for his work in 1936. 
 Another discovery which eluded Irene was that of nuclear fission. In Rome, Enrico Fermi and in Berlin, Otto Hahn and Lise Meitner were bombarding uranium with neutrons in the hope of creating new elements. Fermi was thought to be successful, and his Nobel citation actually mentions this, along with his other achievements. The experiment was repeated in Paris by Irene and her collaborator, Pavel Savitch, but they found no trace of new elements. Instead, they found traces of the already known lighter element, lanthanum, though they could not explain its presence. Hahn was livid by Irene’s objection to his results and refused to read her articles. By this time, Lise Meitner had fled Germany to escape the Nazis. Hahn’s new assistant, Fritz Strassmann, insisted that Hahn go through the paper by Irene and Savitch again. Hahn relented and, being struck by its arguments, repeated the experiment. They established that the uranium nucleus had been split by the neutron, a discovery that fetched Hahn the Nobel prize in Chemistry in 1944, and set up a chain of events that led to the two bombs dropped on Hiroshima and Nagasaki in 1945. Fearful of the military consequences of their research in war-torn Europe, Irene and Frédéric stopped publishing results on fission and put all their documents in the vaults of the French Academy of Sciences two months after the beginning of the Second World War. Those were retrieved ten years later. 
 The two particles which eluded the Joliot-Curies were associated with their triumphal experiment. In 1934, they bombarded aluminium with alpha particles, which resulted in the emission of a neutron and the formation of a new isotope of phosphorus. This isotope was radioactive and emitted a positron. This was the first observation of radioactivity created in the laboratory. Madame Curie was ecstatic about the discovery. The Joliot-Curies were awarded the Nobel Prize in chemistry next year; unfortunately, Irene’s mother was not alive to see the day. 
 The importance of artificial radioactivity can hardly be overestimated. Artificial radioactive isotopes are now regularly used in cancer therapy and medical imaging, such as Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) scans. Industrial uses include food preservation and tracing of leaks and blockage in pipelines, etc. Branches of science that routinely utilise artificial radioactivity include genetic engineering, plant biology, animal physiology, biochemistry, geology and even subjects such as archaeology. 
 In spite of such dedication to science, neither Irene nor Frédéric was an ivory-tower scientist. They held progressive views and were not afraid to articulate them or to put them into practice. Irene and her husband were active against the rising tide of fascism in Europe. Irene served as a minister in the Popular Front government formed by a coalition of communist, socialist and democratic parties, led by Leon Blum, before the Second World War. She played an important role in setting up the National Centre for Scientific Research (CNRS), which later served as a model for many other countries. After Germany occupied France in the Second World War, Frédéric joined the French Communist Party and became active in armed resistance against the Nazis. It was a traumatic time for Irene, who had to bring up her children alone. She was also suffering from tuberculosis. Once Irene and her children had to flee to neutral Switzerland, crossing the border illegally, while Frédéric went underground. The role Frédéric played in the street fighting against the German army, employing his knowledge of chemistry to manufacture bombs, when Paris was on the verge of liberation, has been immortalised in the book ‘Is Paris Burning?’ by Dominique Lapierre and Larry Collins. 
 After the war, both the Joliot-Curies became members of the World Peace Council. Frédéric was appointed the first High Commissioner of Nuclear Energy to head the French nuclear power programme. Irene was also made a commissioner. However, their outspoken opposition to secrecy in nuclear research and to nuclear weapons, as well as sympathy towards socialism, led to their removal within a few years. 
 Over-exposure to radioactivity took its toll, and both Irene and Frédéric became seriously ill. Irene was diagnosed with leukaemia and passed away on March 17, 1956. Frédéric also passed away in 1958. 
 Irene was strong in her convictions. She never patented her discoveries, which would have brought her huge amounts of money. She strongly believed that research is a legacy of mankind as a whole. Her parents, who often had to survive on very little money and carry out research on a shoestring budget, had also refused to take patents on the extraction process of radium. Irene believed in the ideal of a just and fair society. Her sympathy towards the refugees fleeing the fascist regime in Spain was well known, and she lectured on their plight in various countries to draw public attention towards the problem. She was passionate about education for women and served on the National Committee of the Union of French Women. On her 125th birth anniversary, we pay homage to a legendary scientist and great human being. 

Irene Curie speaking at the inauguration of Institute of Nuclear Physics (Photo from the archive of SINP)

 

 

Gautam Gangopadhyay

Monthly Bulletin of the Asiatic Society, June 2022