 A few years later in 1967, Siegbahn published a comprehensive study of XPS, bringing instant recognition of the utility of XPS, which he referred to as Electron Spectroscopy for Chemical Analysis (ESCA).In cooperation with Siegbahn, a small group of engineers (Mike Kelly, Charles Bryson, Lavier Faye, Robert Chaney) at Hewlett-Packard in the USA, produced the first commercial monochromatic XPS instrument in 1969.Siegbahn received the Nobel Prize for Physics in 1981, to acknowledge his extensive efforts to develop XPS into a useful analytical tool.