Journal of Electron Spectroscopy and Related Phenomena, 63 (1993) 307-308 0368-2048/93/$06.00 0 1993 - Elsevier Science Publishers B.V., Amsterdam

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Book Review

NEXAFS Spectroscopy, by Joachim Stohr, Springer Series in Surface Sciences, Vol. 25. ISBN 3-540-54422-4, 403pp, $79.00.

Out of the alphabet soup of acronyms for surface science techniques, NEXAFS is one of the more specialized, being readily available only to the privileged few with access to a synchrotron radiation source. Despite this, near edge X-ray absorption fine structure spectroscopy is a very useful technique whose strength lies in its application to determine the orien- tation and intramolecular bondlength of adsorbed molecules containing low-2 atoms. A NEXAFS experiment entails scanning the energy of a monochromatic photon beam through the region of an adsorbate core level (the absorption edge) and recording the yield of emitted electrons or fluorescent photons. For a molecular adsorbate, intense resonances are seen that correspond to electronic transitions from the core level to unfilled r* or [T* levels. The technique really took off in the mid-1980s with applications to complex molecules that aroused the interest of organic and catalytic chemists, while the idea that “shape” resonance energies for quasi-diatomics were quite simply correlated with intramolecular bond- length has excited fierce passions and much debate. The applicability of NEXAFS is illustrated by an appendix to this book listing some 64 mole- cules whose spectra have been analysed, some on several different sub- strates, making at least 143 different surface systems, plus numerous polymers and Langmuir-Blodgett films, and some reaction intermediates.

Joachim Stohr’s NEXAFS Spectroscopy is an excellent book on the subject, taking the reader in logical stages from the fundamentals of inner shell excitation and molecular orbitals, through computational schemes and a detailed description of how to perform synchrotron radi- ation X-ray absorption experiments, including ways of analysing spectra to obtain quantitative information, and finishing with discussion of many examples of new insights into surface bonding derived from NEXAFS. There is also a short chapter speculating on new directions. I could not think of anything relevant to the subject that has been omitted, and the text is nicely readable. Jo Stohr has been involved in about half of all the NEXAFS work yet published, making him the ideal person to write this monograph. The book contains quite a lot of new, unpublished material,

308 J. Electron Spectrosc. Relat. Phenom. 63 (1993) 307-308

and all NEXAFS work - not just that by the author and his collaborators - is fairly treated. New understandings are still emerging, and some previous conclusions are retracted or modified, but it is always made clear when this is the case.

The only weak point of the book is its index, which is too sketchy to be really useful in a reference book. If one wants to find, for instance, all the references to benzene, the index merely gives the one place that it appears as a major chapter sub-heading, with an appendix listing the pages where its spectra are depicted.

This book will be required reading for all surface spectroscopists, not just the small band of existing NEXAFS practitioners, and this is the ideal place to look up the present state of knowledge of molecular bonding at surfaces. Many other scientists will also find it useful, because Jo Stijhr’s treatment forms a good introduction to topics such as orbitals and symmetry, manag- ing to unify the physicist’s and the chemist’s often disparate ways of looking at molecules.

David Norman SERC Daresbury Laboratory