Siegbahn. Kai

Since the beginning of the 1970s, quantum mechanical methods have increasingly been applied to polymers. One of several reasons for this is the improvement of experimental techniques for investigating the electronic properties of polymers, such as photoelectron spectroscopy (PS) and, especially. X-ray induced photoelectron spectroscopy (XPS), sometimes known as ESCA. The development of the latter has been mainly due to the efforts of Kai Siegbahn (Nobel prize in 1981) in Uppsala. In polymer chemistry, two pioneering papers were published in 1972. They refer to the experimental ESCA analysis of the core levels of fluoropolyethylenes [34] and of the valence band of polyethylene... 

X-ray photoelectron spectroscopy (XPS) is widely used for surface characterization and analysis of polymers, biomedical materials and paper. The technique was developed by Kai Siegbahn in the 1960s, who realized that technical development had come to a point where the photoelectric effect discovered by Einstein could be used for surface chemical analysis. The photoelectric effect is the phenomenon that occurs when a material is exposed to photons with sufficiently high energy and electrons contained in the material with a lower binding energy are emitted. Therefore, we can write ... 

Prof. Kai Siegbahn of Uppsala University, Uppsala, Sweden, is the person who gave birth to XPS and finessed it into a powerful technique in a short time, after his observation and discovery of chemical shift in sodium thiosulfate. The publications of his two books [2,3], one mainly on solids and the other on free molecules established XPS as a versatile analytical tool applicable to a large field of science. Every month more than a hundred publications appear in which XPS is used to elucidate the properties of the surface or bulk. Carlson [4] gives a comprehensive account of the XPS technique in his book. On account of the great impact XPS has made to scientific progress. Prof. K. Siegbahn was awarded the Nobel prize for Physics in 1981. 

X-ray [1] photoelectron spectroscopy, is based on the photoelectric effect discovered by Heinrich Hertz in the late 1800s [2]. Later in 1905, Albert Einstein described the process in quantum mechanical terms [3]. It was not until the mid-1960s that Kai Siegbahn and his research group at the University of Uppsala, Sweden developed the technique into a practical analytical method [4]. 

In common with most other spectroscopic methods, ESCA is a technique originally developed by physicists and now gradually being taken over by chemists to be developed to its full potential as a tool for investigating structure and bonding. The technique has largely been developed by Professor Kai Siegbahn and his collaborators at the University of Uppsala over the past twenty years or so, and much of the early work has been extensively documented in the first ESCA book. It is only within the last decade, however. 

There is little doubt that one of the most versatile and powerful spectroscopic methods is electron spectroscopy for chemical analysis, ESCA (also termed X-ray photoelectron spectroscopy, XPS), developed in the 1950s by the Swedish scientist Kai Siegbahn (winner of the Nobel Prize in Physics for this discovery in 1981). The method has been long commercialized and is currently extensively used for surface analysis. ESCA provides information on the relative amounts of different elements on the surface of materials, with a depth of analysis of only 2-10 nm. Information on the chemical environment for the elements, e.g. oxidation state, can also be obtained for many samples. Various types of materials (organic, inorganic, surfaces, powders, fibres) can be analysed with this technique. A combination of ESCA and AFM can help us identify whether differences in properties over a surface are due to heterogeneity in topography/surface structure or to chemistry. 

It is very much appreciated that all the 1981 Nobel laureates, Nicolaas Bloembergen, Arthur Schawlow and Kai Siegbahn, were able to attend and deliver their invited talks. Professor Schawlow summed up the conference and this too is presented here. The conference also benefited considerably from the presence of Professor I.l. Rabi, who gave a much appreciated talk at the conference dinner. As this talk was given without a manuscript, it could unfortunately not be included here. 

The development of this technique resulted in the award of the Nobel Prize in physics to Kai Siegbahn of Sweden. Here, the sample is exposed to a beam of X-rays (although synchrotron radiation has been used), causing ejection of both valence and more deeply held (core-level) electrons. Experimentally, by far the most work has been accomplished with X-ray sources MgKa at 1253.6 eV and AlKa at 1486.6 eV, and most studies have been related to solid samples and core-level spectra. A very important feature of X-ray photoelectron spectroscopy (XPS) is that it is a surface-sensitive technique. Electrons produced by X-ray beam ionization are greatly attenuated by collision with sample atoms or molecules according to the expression... 

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