:Kai Siegbahn

{{Infobox scientist

| name = Kai Siegbahn

| image = Kai Manne Börje Siegbahn 2.jpg

| caption =Siegbahn in 1981

| birth_date = {{Birth date|1918|4|20|df=y}}

| birth_place = Lund, Sweden

| death_date = {{death date and age|2007|7|20|1918|4|20|df=y}}

| death_place = Ängelholm, Sweden

| field = Physics

| work_institution = Stockholm University
University of Uppsala

| alma_mater = Stockholm University

| doctoral_advisor =

| doctoral_students =

| known_for = {{no wrap|X-ray photoemission spectroscopy}}

| prizes = Nobel Prize in Physics (1981)
Björkén Prize (1955, 1977)

}}

Kai Manne Börje Siegbahn (20 April 1918 – 20 July 2007) was a Swedish physicist who shared the 1981 Nobel Prize in Physics.{{cite news |title=Kai Siegbahn, Swedish Physicist, Dies at 89|author=Jeremy Pearce |url=https://www.nytimes.com/2007/08/07/world/europe/07siegbahn.html |work=The New York Times |date=7 August 2007}}

Biography

Siegbahn was born in Lund, Sweden, son of Manne Siegbahn the 1924 physics Nobel Prize winner. Siegbahn earned his doctorate at the Stockholm University in 1944. He was professor at the Royal Institute of Technology 1951–1954, and then professor of experimental physics at Uppsala University 1954–1984, which was the same chair his father had held.{{cite journal|author=Hagstrom, Stig B.|author-link=Stig Hagström|title=Obituary: Kai Manne Börje Siegbahn|journal=Physics Today|date=November 2007|volume=60|issue=11|pages=74–75|doi=10.1063/1.2812132|doi-access=free}} He shared the 1981 Nobel Prize in Physics with Nicolaas Bloembergen and Arthur Schawlow. Siegbahn received half the prize "for his contribution to the development of high-resolution electron spectroscopy" while Bloembergen and Schawlow received one quarter each "for their contribution to the development of laser spectroscopy".{{cite web|url=https://www.nobelprize.org/prizes/physics/1981/summary/|title=The Nobel Prize in Physics 1981|work=Nobel Foundation|access-date=27 September 2023}}

Siegbahn referred to his technique as Electron Spectroscopy for Chemical Analysis (ESCA); it is now usually known as X-ray photoelectron spectroscopy (XPS). In 1967 he published a book, ESCA; atomic, molecular and solid state structure studied by means of electron spectroscopy.{{cite web|url=https://www.nobelprize.org/uploads/2018/06/siegbahn-lecture-1.pdf|title=Kai Siegbahn - Nobel lecture: Electron Spectroscopy for Atoms, Molecules and Condensed Matter|date=8 December 1981|work=Nobel Foundation}}

He was a member of several academies and societies, including the Royal Swedish Academy of Sciences, and was president of the International Union of Pure and Applied Physics from 1981 to 1984.{{cite web|url=https://www.nobelprize.org/prizes/physics/1981/siegbahn/26284-curriculum-vitae/|title=Kai Siegbahn - Curriculum Vitae|access-date=14 September 2023|work=Nobel Foundation (From Nobel Lectures, Physics 1981-1990, Editor-in-Charge Tore Frängsmyr, Editor Gösta Ekspong, World Scientific Publishing Co., Singapore, 1993)}}

Siegbahn married Anna Brita Rhedin in 1944. The couple had three sons (two physicists and a biochemist).{{cite journal|title=Kai M. Siegbahn (1918‒2007): a pioneer in high-resolution electron spectroscopy|author=Magdolna Hargittai|journal=Structural Chemistry|date=January 2022|volume=33|pages=307–310|doi=10.1007/s11224-021-01865-0|doi-access=free}}

Siegbahn died on 20 July 2007 at the age of 89. At the time of his death he was still active as a scientist at the Ångström Laboratory at Uppsala University.