Noted for modernizing Swedish physics, Karl M. G. Siegbahn contributed significantly to the field of x-ray spectroscopy begun in Germany and England. His design and application of equipment and techniques in this field vastly improved the accuracy of existing methods by which x-ray wavelengths were distinguished, and led to important discoveries about the nature of X rays (electromagnetic radiation invisible to the unaided human eye) and atomic structure. In recognition of his work, Siegbahn was awarded the 1924 Nobel Prize in Physics. He became the first director of the Nobel Institute of Experimental Physics in 1937, and remained director of the institute until his retirement in 1964.

Karl Manne Georg Siegbahn was born in Örebro, Sweden, on December 3, 1886. His father was Nils Reinhold Georg Siegbahn, a station master for the Swedish national railway system, and his mother was the former Emma Sofia Mathilda Zetterberg. After his father's retirement, the family...