Kai Siegbahn

Kai Manne Börje Siegbahn was born on April 20, 1918, in Lund, the son of Nobel laureate Manne Siegbahn. Educated at the University of Uppsala and the University of Stockholm, he served as Professor of Physics at the Royal Institute of Technology (KTH) and later held his father's former chair at Uppsala University from 1954 to 1984.

Beginning in the 1950s, Siegbahn developed ultra-high-resolution electron spectrometers to analyze electrons ejected from matter by X-rays. He discovered that electron binding energies undergo subtle 'chemical shifts' depending on the chemical bonding of atoms, creating ESCA (Electron Spectroscopy for Chemical Analysis), today known as X-ray Photoelectron Spectroscopy (XPS)—an indispensable tool in surface chemistry, semiconductor fabrication, and metallurgy. He received the 1981 Nobel Prize in Physics.