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David Nordfors
Abstract Free molecules have been studied by means of photoelectron spectroscopy and quantum theoretical calculations. Core level shake-up spectra, binding energy shifts and valence spectra have been recorded for alcohols, carbonyls and other compounds containing first.row elements. A simple model is developed for core binding energy shifts, relating shifts directly to molecular topology. Shifts are used in a thermochemical model including the equivalent core apporximation in order to predict proton affinities for isoelectronic compounds. The model is studied in detail, and correlations between core electron binding energies of isoelectronic compounds are unveiled. The limitations of the equivalent core approximation, e.g. valence-core penetration, are investigated by means of ab initio MCSCF computations. Shake-up states in the low energetic pi-pi* region have been studied. The experimental spectra are assigned in terms of molecular orbitals. Shake-up envelopes in the intermediate energy region contain a multitude of sigma- and Rydberg states and shake-off thresholds. They display characteristic peatures which are specific for the core ionized active group. Calculation of the shake-up/shake-off envelope are made for HCl using a Stieltjes imaging technique involving local and continuum orbitals. Deuteration effects on vibrationally broadened states in XPS are observed. The linewidths are related to the ground state vibrational frequencies (IR frequencies). Potential surfaces and related properties and spectra of ozone have been investigated using an MCSCF technique involving response functions and analytical molecular gradiants and Hessians. |