Chemical Spectroscopy and Photochemistry in the Vacuum-Ultraviolet

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.

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Proceedings of the NATO Advanced Study Institute, Valmorin, Québec, Canada, August 5-17, 1973

Contenu
Vacuum Ultraviolet and Photoelectron Spectroscopy Historical Background and Survey.- Aspects of Molecular Rydberg States.- Photoelectron Spectroscopy.- Absolute Intensities and Classification of Transitions in Electron Impact Spectroscopy.- Photoionization of Free Radicals.- Photoelectron Spectroscopy of Molecular Beams.- High Resolution Vacuum Ultraviolet Spectroscopy of Diatomic Molecules.- Optical Properties of Liquids in the Vacuum UV.- The Far Ultraviolet Absorption Spectra of Organic Molecules: Lone Pairs and Double Bonds.- The Ethane Problem.- A Pot-Pourri of Ultraviolet and Photoelectron Spectra of Iodides.- Beyond the Orbital Approximation.- Natural and Magnetic Circular Dichroism Spectroscopy in the Vacuum Ultraviolet.- (H3C)2C=C(CH3)2, (H3C)2BN(CH3)2, (H3C)BF and (H3C)3B. Further Evidence for a ? ? ?* Assignment of the OLEFIN UV Mystery Band.- Photoelectron Spectra of Moderate Sized Molecules.- HAM a Semi-Empirical MO Theory.- Ab Initio Calculations for Excited States of Molecules.- Threshold Electron-Impact Spectroscopy.- Spectra of Free Radicals and Molecular Ions Produced by Vacuum Ultraviolet Photolysis in Low-Temperature Matrices.- Rydberg States of Diatomic and Polyatomic Molecules.- Theory of Intravalency and Rydberg Transitions in Molecules.- On the Assignment of Molecular Rydberg Series.- On Molecular Rydberg Term Values.- Correlation of Molecular and Rare Gas Term Values.- On the Possibilities of Studying the Electronic Structure of Organic Molecules through the Analysis of the Wave Function.- The Early Years of Photochemistry in the Vacuum Ultraviolet.- Photoionization and Fragmentation of Polyatomic Molecules.- Far Ultraviolet Photochemistry of Organic Compounds.- Energy Partioning in the Photochemistry of Alkanes.- RecentStudies of the Fluorescence from Some Hydrocarbon Molecules.- Production of Electronically Excited Species in Photodissociation of Simple Molecules in the Vacuum Ultraviolet.- Energy Partitioning in the Photofragments.- Generation of Coherent Light in the Vacuum Ultraviolet.- Synchrotron Radiation as a Light Source.- Optical Studies of Molecular Crystals in the Vacuum Ultraviolet Using Synchrotron Radiation.- Photochemistry of Planetary Atmospheres and Interstellar Molecules.