Heinrich Gustav Johannes Kayser (16.03.1853 —14.10.1940) was a German experimental physicist. He was born in Bingen. In 1873—79 he studied at the universities of Strasbourg, Munich and Berlin. In 1879 he received the degree of Doctor of Philosophy in Berlin under H. Helmholtz. In 1878 — 85 he worked at the Institute of Physics in Berlin, in 1885—94 he was professor at the Higher Technical School in Hanover and in 1894—1920 at the University of Bonn and director of the Institute of Physics.
His research was mainly in the field of spectroscopy. Together with C. Runge he established the spectral series of many elements, in particular of the alkali and alkaline-earth elements. He created a system of accurate normalising units for measuring wavelengths and determined with high accuracy the wavelengths of the spectral lines of many elements, in particular the lines of iron, of the noble gases and of other very simple spectra.
He separated the true spectral lines of the elements from lines belonging to contaminants. He processed and systematised an enormous number of spectra of various chemical elements. He laid the foundations of atomic spectroscopy. He was the author of a well-known multi-volume handbook of spectroscopy.
A Fellow of the Royal Society (1911) and a member of the St Petersburg Academy of Sciences (1902).