EXPANDED OBSERVATIONS. “Two years after Einstein’s publication, in 1907, P.D. Innes, a PhD student at that time, experimented with a Röntgen tube, Helmholtz coils, a magnetic field hemisphere (an electron kinetic energy analyser), and photographic plates, to record broad bands of emitted electrons as a function of velocity, in effect recording the first XPS spectrum.” (XPS = X-ray photoelectron spectroscopy).
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