Siegbahn was born to Karl M. G. Siegbahn and Karin Högbom Siegbahn on April 20, 1918, in Lund, Sweden. His father was a lecturer in physics at the University of Lund and the director of the Nobel Institute for Physics of the Royal Swedish Academy of Sciences for nearly thirty years. The elder Siegbahn's discoveries and research in X-ray spectroscopy won him the 1924 Nobel Prize in physics.
The younger Siegbahn pursued his interests in mathematics, physics, and chemistry at the University of Uppsala, from which he earned his bachelor of science degree in 1939 and his master of science degree in 1942. He received his doctorate in 1944 from the University of Stockholm and worked as a researcher from 1942 to 1951 at the Nobel Institute of Physics. After a few years as a physics professor at the Royal Institute of Technology in Stockholm, Siegbahn left in 1954 to become professor and then head of the Physics Department at the University of Uppsala, where he remained and conducted his important research.
It was while he was pursuing his graduate degree that Siegbahn's interest in spectroscopy developed. Spectroscopy studies the frequencies, or wavelengths, at which particles of matter emit light or radiation. Since the frequencies are specific, or characteristic, of the matter being studied, they can yield valuable information about the atomic and molecular structure of that matter. Heinrich Hertz had discovered the photoelectric effect in 1883: objects struck by ultraviolet light release electrons, called photoelectrons. The nature of the effect was further examined by Max Planck and Albert Einstein, and researchers, hoping to advance scientific knowledge about the composition of matter, began attempting to use spectroscopy to analyze the photoelectrons. Electrons collide and scatter as they leave matter, losing unknown amounts of energy and creating spectra that are very difficult to read. Existing spectroscopes were inadequate to analyze the particles, but Siegbahn solved this problem.
When he was in graduate school during the 1940s, Siegbahn studied electrons given off by radioactive nuclei, a process called beta decay. If he could measure the energies of these beta-ray electrons, he could learn much more about the nuclei. Existing instruments were of limited use for this purpose, so Siegbahn developed a mushroom-shaped magnet that allowed focusing in two directions. Siegbahn's high-resolution instrument increased the accuracy of measurements of these photoelectrons ten times. By the 1950s Siegbahn had turned his attention to electron spectroscopy--knocking electrons out of nonradioactive atoms with light or X rays--to determine the energies that bind electrons to atoms. Again, he found the spectroscopes he was using unable to produce accurate measurements. He decided to apply the double-focusing method he had developed for nuclear physics to the energy spectra of photoelectrons. The outcome was a double-focusing spectrometer with a high resolution that revealed previously unseen, narrow, but well-defined electron lines.
Siegbahn and his colleagues completed the first high-resolution, double-focusing spectrometer in 1954, and again it improved measurement accuracy tenfold. In 1957 the team recorded the first extremely sharp lines that allowed precise measurement of binding energies. In the 1960s the usefulness of the device was greatly extended when Siegbahn and two fellow researchers found that their electron spectrometer also revealed the chemical environment of the atoms that released the photoelectrons being studied, yielding details about chemical bonding as atoms combined into molecules. The technique now became known as electron spectroscopy for chemical analysis, or ESCA. Siegbahn and his team also adapted ESCA for the analysis of gases and liquids as well as solids.
Siegbahn's ESCA technique changed electron spectroscopy from a laboratory concept with a very limited application to a widely used tool. ESCA provides high-resolution analysis of the atomic, molecular, and chemical characteristics of a nearly unlimited range of scientific, commercial, and industrial materials that includes atmospheric pollutants and surface corrosion. To acknowledge his contribution, Siegbahn was awarded the 1981 Nobel Prize in physics for his role in the development of a technique that provided a better understanding of the nature of matter.
Now in his 80s, Siegbahn is a professor emeritus at Uppsala University's Materials Research Laboratory.
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