A Discussion on photoelectron spectroscopy - Electron spectroscopy for chemical analysis (e.s.c.a.)

Abstract

The electronic structure of matter has so far been studied almost exclusively by means of the electromagnetic radiation which is being emitted (or absorbed) at excitation. Apart from some early attempts, the electrons themselves were not directly detected. The various energy levels which could be studied by different modes of excitations were observed as photons being emitted (or absorbed) when electrons were making quantum jumps between two levels. Over a long period of time spectroscopy in the visible, infrared, ultraviolet, and X-ray parts of the electromagnetic spectrum was gradually perfected and extensively used in many kinds of applications. More recently, other and in some cases more sophisticated techniques, like n.m.r., e.p.r. and microwave spectroscopy, have been added to previously existing spectroscopic tools. During the last decade serious attempts have been made to explore the possibility of developing a spectroscopy based on the direct observation of the electrons. The results are encouraging. Despite many initial experimental difficulties it now seems evident that these can be solved in a surprisingly satisfactory way. Moreover, new types of information have become accessible and the fields of application are numerous.