Kai Siegbahn

Kai Siegbahn (1918–2007) was a Swedish physicist who developed electron spectroscopy for chemical analysis (ESCA), now commonly called X-ray photoelectron spectroscopy, and shared the 1981 Nobel Prize in Physics.

Photoelectric effect: The emission of electrons from matter after it absorbs electromagnetic radiation. Its energy-conservation principle underlies the photoelectron measurements central to Siegbahn’s method.
1981 Nobel Prize in Physics: The Physics Nobel Prize awarded to Nicolaas Bloembergen, Arthur Schawlow, and Kai Siegbahn for contributions to laser and electron spectroscopy. The award recognized Siegbahn’s development of high-resolution electron spectroscopy for chemical analysis.
Manne Siegbahn: A Swedish physicist awarded the 1924 Nobel Prize in Physics for discoveries and research in X-ray spectroscopy. Kai Siegbahn was his son and pursued a related spectroscopy tradition.
Auger electron spectroscopy: A surface-analysis method that identifies elements by measuring electrons emitted through the Auger effect. It also analyzes surfaces with electrons, but uses a different emission process from ESCA.
X-ray photoelectron spectroscopy: A surface-analysis technique that identifies elements and chemical states by measuring electrons emitted after X-ray irradiation. This is the modern name for the analytical spectroscopy Siegbahn developed.
Surface analysis: The measurement of a material’s surface composition, structure, and chemical state. ESCA made detailed chemical analysis of solid surfaces widely practical.
Nicolaas Bloembergen: A Dutch-American physicist whose work on nonlinear optics earned him the 1981 Nobel Prize in Physics. He shared the 1981 Physics Nobel with Siegbahn for distinct contributions to spectroscopy.
Energy-dispersive X-ray spectroscopy: An analytical technique that identifies elements by measuring characteristic X-rays emitted from a sample. It detects emitted X-rays rather than the photoelectrons measured in Siegbahn’s method.
Electron binding energy: The energy required to remove an electron from a specified state in an atom, molecule, or solid. Siegbahn’s measurements made shifts in binding energy useful for identifying chemical environments.
Chemical state analysis: The identification of an element’s bonding and oxidation environment from characteristic measurement signals. Siegbahn’s method revealed chemical state, not merely which elements were present.

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