Overview

This book contains spectra of the doubly charged positive ions (dications) of some 75 molecules, including the major constituents of terrestrial and planetary atmospheres and prototypes of major chemical groups. It is intended to be a new resource for research in all areas of molecular spectroscopy involving high energy environments, both terrestrial and extra-terrestrial. All the spectra have been produced by photoionisation using laboratory lamps or synchrotron radiation and have been measured using the magnetic bottle time-of-flight technique by coincidence detection of correlated electron pairs. Full references to published work on the same species are given, though for several molecules these are the first published spectra. Double ionisation energies are listed and discussed in relation to the molecular electronic structure of the molecules. A full introduction to the field of molecular double ionisation is included and the mechanisms by which double photoionisation can occur are examined in detail. A preliminary chapter covers double photoionisation of an atom in order to explain the basic principles of the technique, then five chapters present spectra of molecules of increasing size. A seventh chapter on the new fields of core-core and core-valence double ionisations, with selected examples, completes the main body of the book. Appendices explain the detailed mechanisms of double photoionisation, the calibration of the electron spectrometers, and give a brief summary of the methods by which double ionisation energies are calculated theoretically.