Kai M. Seigbahn half the 1981 Nobel Prize in physics "for his contribution to the development of high-resolution electron spectroscopy.” The other half of the prize was won jointly by Nicolaas Bloembergen and Aruthur L Schawlow"for their contribution to the development of laser spectroscopy. Kai Seigbahn researched various areas of spectroscopy and designed instrumentation to conduct his research. He began in nuclear spectroscopy, measuring energy levels of several atomic nuclei. In the 1950s he designed an electron spectrometer to measure atomic energy levels (energy levels of electrons bound to an atom). His atomic spectroscopy work continued to include designing instrumentation and measuring binding energies of molecules.