Siegbahn, Karl Manne Georg (1886–1978)

Swedish physicist who was awarded the Nobel Prize for Physics in 1924 for his work in the field of X-ray spectroscopy – the study of the X-rays produced by bombardment of a sample with electrons or photons. Each element emits X-rays with characteristic wavelengths and these can be used to identify the sample. The X unit or Siegbahn unit, used for expressing wavelengths of X-rays and gamma rays, is named after him. One Siegbahn unit equals 1.00202 × 10−13 m.

He began his studies in X-ray spectroscopy in 1914. By gradually refining his equipment and technique, Siegbahn was able to measure the wavelengths of X-rays with unprecedented accuracy. This enabled him to make corrections to the theory of X-ray diffraction and discover several new series of X-ray spectral lines. He also developed the use of the diffraction grating for studying longer wavelengths. In 1925 Siegbahn and his colleagues proved that X-rays are bent or refracted as they passed through prisms, in the same way as light, and thus were of the same nature as light.

Siegbahn was educated at the University of Lund, Sweden, obtaining his doctorate in 1911.