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Technology

The technology that won Irene and Frederic Joliot-Curie the Nobel Prize in 1935 was for their work on “synthesis of radio-elements.”  This work was a continuation of the discovery of radio-elements which had won both of Irene’s parent’s the Nobel prize in 1903. (Joliot-Curie)

 

Irene and Frederic’s work began in the early part of 1932 with the repetition of Pierre Auger’s work on the cloud chamber experiment. (Leone & Robotti, 2010) According to the Jefferson Lab, “the cloud chamber is a simple device that allows you to observe the decay of radioactive materials.” Although it was not so simple at the time. When the Joliot-Curie team repeated this method they used a stronger magnetic field with a filter that absorbed the natural gamma radiation. During this experiment they noticed that several electrons were acting strangely in regard to the magnetic field, they were curving in opposite directions than the others. Their hypothesis for this occurrence was that the “curves seemed…to indicate the slight production of secondary rays within the lead absorber.” Irene and Frederic also found that within this magnetic field there was evidence of several positive particles. (Leone & Robotti, 2010)

 

Cloud Chamber

Cloud Chamber

Later  the Joliot-Curie team’s study lead them to be able to “obtain by transmutation new radioactive elements.” (Joliot-Curie) According to Merriam-Webster’s definition, transmutation is “the conversion of one element into another either naturally or artificially.” In this study they had some difficulties interpreting “the emission of neutrons by fluorine, sodium, and aluminum.” They found that Aluminum could be “transformed into a stable silicon atom,” but if the neutron is released then the end result is an unknown atom. (Joliot-Curie)

 

They then observed that certain elements like aluminum and boron do not emit just protons and neutrons but also positive electrons when they are irradiated by alpha rays. Merriam-Webster’s definition of irradiated is ” to affect or treat by radiant energy (as heat).” While working on the discharge of the positive electrons they noticed a crucial  difference between the elements that had undergone transmutation and the others produced, all of the reactions were “instantaneous phenomena explosions.” This experiment also showed that the positive electrons that had been produced by aluminum continued to be emitted even after they were removed from the source. They found that this shows true radioactivity. (Joliot-Curie)

 

In the conclusion to this research and testing, Irene and Frederic believed that this phenomenal occurrence takes place in two steps. The first part is “the capture of the alpha particle and the instantaneous expulsion of the neutron, with the formation of a radioactive atom which is an isotope of phosphorus of atomic weight 30, while the stable phosphorus atom has an atomic weight of 31.” Thus the radiative isotope is unstable. The second step in the unstable atom, the radio-element, which they called “radio-phosphorus”, decomposes by half within three minutes. They also found this research and technique applicable to boron and magnesium. (Joliot-Curie)

 

Curie and Joliot’s discovery made it possible to inexpensively and artificially prepare artificial radioactive atoms. “The tedious labor and high cost of separating naturally occurring radioactive elements like radium from their ores would no longer impede the progress of nuclear physics and medicine.”  Irene and Frederic could have no idea on how nuclear power would affect the world today, but they were hopeful that it would help humanity, not just “pure science,…physiologists, [and] doctors.” (Curies)

The 1935 Nobel Laureates at the Nobel Prize Award Ceremony in the Golden Hall of the Stockholm City Hall, 10 December 1935. From left: James Chadwick, Irène Joliot-Curie, Frédéric Joliot and Hans Spemann. Copyright © Association Curie Joliot-Curie

The 1935 Nobel Laureates at the Nobel Prize Award Ceremony in the Golden Hall of the Stockholm City Hall, 10 December 1935. From left: James Chadwick, Irène Joliot-Curie, Frédéric Joliot and Hans Spemann. Copyright © Association Curie Joliot-Curie

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