Pierre Ausloos - Böcker

This volume presents the proceedings of a 1986 Advanced Study Institute entitled "Structure/Reactivity and Thermochemistry of Ions", held at Les Arcs, France, June 30 to July 11, 1986. The format of a NATO Institute is ideally suited to in-depth communications between scien­ tists of diverse backgrounds. Particularly in the field of ion physics and chemistry, where on-going research involves physicists, physical chemists, and organic chemists - who use a variety of experimental and theoretical techniques - it is found that in the relaxed but stimula­ ting atmosphere of a NATO ASI, each professional group provides unique insights, leading to a better definition and solution of problems relating to the properties of gas phase ions. This book presents chapters based on the lectures presented at the Les Arcs ASI. The participants took the initiative to organize a number of specialized workshops - informal discussion groups which considered questions or problem areas of particular interest. The accounts of these sessions, which are also included in this book, make stimulating reading, and include considerable useful information. This Advanced Study Institute is the fourth in a series of NATO-spon­ sored institutes devoted to the chemistry and physics of ions in the gas phase. The first, in 1974, in Biarritz, France, focussed on "Interactions between Ions and Molecules".

It is probably safe to predict that the future of chemistry is linked to the excited states of molecules and to other short lived species, ions and free radicals. Molecules have only one ground state but many excited states. However large the scope of normal, ground state chemistry might be, above and beyond it lies the world of excited states, each one having its own chemis­ try. The electronic transitions leading to the excited states, either discrete of continuous, are examined in molecular elec­ tronic spectroscopy. Electronic spectroscopy is the queen of all spectroscopies: for if we have the resolution we have everything. Vnfortunately, the chemist who is interested in the structure and reactions of larger molecules must often renounce all that infor­ mation. The spectra are complex and often diffuse; resolution does not always help. To understand such spectra he must look at whole families of molecules; to some extent structural analogies help. Let us call this chemical spectroscopy and handle it with care. In order to understand the properties of molecules we also need theory. We know that molecular problems are, in principle, soluble by the methods of quantum mechanics. Present time quan­ tum chemistry is able to provide a nearly accurate description of not too large molecules in their ground states. It is probablY again safe to predict that the future of quantum chemistry is connected with molecular excited states or, generally spoken, the accurate handling of the open-shell problem.