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Hugo Atterling's scientific memoir of Manne Siegbahn explains how apparatus and source composition shaped early X-ray spectroscopy. One example traces two unexpected lines in a 1914 spectrum to a silver layer beneath a platinum coating, observed in first and second diffraction orders. The account connects identification of a chemical element with the interpretation of the instrument, rather than treating each observed line as a new property of the nominal target. His memoir also documents the development of precision and vacuum spectrometers.^[ref]

Physics.^[ref]

Manne Siegbahn developed precision X-ray spectroscopy for investigating atomic structure. A crystal converts an X-ray wavelength into a diffraction angle through Bragg's law. Careful control of the crystal geometry, angular calibration, spectral resolution and instrumental absorption therefore determines which characteristic spectral lines can be distinguished. His instrumentation resolved relationships and small differences that a coarser spectrometer would merge, making precision measurement part of the explanation of atomic X-ray spectral lines.^[ref]

Physics.^[ref]