Siegbahn, Kai Manne Borje, 1918–2007, Swedish physicist, son of Karl Siegbahn. He earned his doctorate at the Univ. of Stockholm in 1944 and later taught at the Royal Institute of Technology, Stockholm (1951–54), and the Univ. of Uppsala (1954–84). He shared the 1981 Nobel Prize in Physics with Nicolaas Bloembergen and Arthur Schawlow for their work in spectroscopy. Siegbahn developed techniques for chemical analysis using high-resolution electron spectroscopy.