On July 9, 2018, Sotheby's passed a lot constituted by the medals and diplomas of both physicists. I introduced their work as follows before the sale. Kai Siegbahn's medal and diploma are not included in the next RR sale.
The suite of scientific works rewarded by the Nobel Prizes provides an excellent historical vision of the most promising openings brought by the discoveries. The Nobel Prize in Physics highlights the cathodic rays twice, in 1901 and 1905, followed by X-ray spectroscopy in 1914 and 1917 and X-ray crystallography in 1915.
Henry Moseley, killed on the field of honor in 1915 at the age of 27, did not get the Nobel Prize. He would have deserved it by the importance and variety of his contributions including the empirical law connecting the X-spectrum of an element to its atomic number.
From 1914 Manne Siegbahn studied X-ray spectroscopy with Rydberg at Lund University. A brilliant engineer, he greatly improved the resolution of the measurements, resulting in a classification and mapping of the Moseley spectra. In 1922 he became a professor at the University of Uppsala. He published his results in 1923 under the title Spektroskopie der Röntgenstrahlen.
In 1924 the Nobel Committee failed to appoint a laureate in physics. In 1925 this prize is awarded retroactively to Siegbahn.
Kai Siegbahn followed in the steps of his father. Using the photoelectric emission, he obtained high precision measurements of the energy levels in the atoms. He shared the Nobel Prize in Physics in 1981 with two specialists in laser spectroscopy.