In the 1900s, there began a mad rush to discover new elements. Yvette Cauchois (1909-1999) joined that hunt and made several key contributions and discoveries.
Cauchois’s first contribution centers around the field of spectroscopy. When atoms of elements are exposed to energy, they emit photons with very specific energies. This is because the energy absorbed by the atom causes an electron to move to a higher energy level and fall back down. When the electron returns to its starting energy level, the energy gained by this excitation is emitted as a photon with a characteristic wavelength.
By the mid-19ths century, it was known that there is a link between the atomic number of an element and the x-ray spectrum, which is produced after conducting x-ray spectroscopy. But for rare earth elements or rare gases or really heavy elements, the x-ray spectrums were very hard to observe and read because they were only found in trace amounts. Thus, the lines of their spectrums were very faint.
But Cauchois developed a new technique to make it possible to measure these x-ray emission lines, despite their low intensity. She chose a curved crystalline slate, which reflected light differently, allowing for a greater gain in luminosity. This caught spectral lines that hadn’t been observed before. Thus, Cauchois was able to provide information on the x-ray spectra emitted by xenon and argon, which previously hadn’t been seen. This technique was named the Cauchois spectrograph.
After Cauchois made this discovery, Romanian nuclear physicist Horia Hulubei (1896-1972) enlisted her and her new instrument in his work on discovering unknown elements. Working together, Cauchois and Hulubei observed the L-spectrum of polonium and were able to confirm its atomic number as 84. In 1939, the duo also published in the Compte rendus de l’Académie des sciences claiming that they had discovered the natural element 93, however, this discovery was later abandoned.
From 1975-1978, Cauchois served as the second female president of the Société Française de Chimie Physique. The first president had been Marie Curie. Later on, Caushois continued to research UV spectroscopy to study light elements.