Siegbahn, Karl Manne Georg, 1886–1978, Swedish physicist. In 1913, he began a series of experiments that led to the discovery of the M series of X rays and demonstrated the shell arrangement of electrons within the atom. In the process, he developed equipment and techniques that established X-ray spectroscopy as a useful tool. For that work, he was awarded the 1924 Nobel Prize for Physics. He later served (1937–64) as the director of the Nobel Institute of Physics in Stockholm.
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