Gustav Robert (ˈɡʊstaf ˈroːbɛrt). 1824–87, German physicist. With Bunsen he developed the method of spectrum analysis that led to their discovery of caesium (1860) and rubidium (1861): also worked on electrical networks
(kîr'kôf') German chemist who with Robert Bunsen discovered the elements cesium and rubidium. He also investigated the solar spectrum and researched electrical circuits and the flow of currents. His electromagnetic theory of diffraction is still the most commonly used in optics.