Core Level Photoelectron Spectroscopy Of Small Molecules PDF Download

The photoelectron spectra of a series of halogenated molecules have been investigated in the gas phase. Both core-ionization energies and Auger kinetic energies were measured to probe the nature of the interaction that holds a core electron to the molecule. It was found that satellite structure (shake) could be used to predict the amplitude attenuation in the Br2 EXAFS spectrum. Inclusion of multielectron processes into the theory that predicts the EXAFS amplitude provides a more accurate representation of the EXAFS spectrum if certain assumptions about the threshold of shake are valid. The satellites can be used to investigate the nature of the transitions themselves. In the case of argon, the transitions arise from Rydberg processes that excite a 3p valence electron to the 4p or 5p. In addition, the shake structure allows a measurement of the relaxation energy. The difference between the average energy of a spectrum, including shake, and the energy of the main peak in that spectrum is equal to the difference between the Koopmans' theorem "frozen orbital" state and the fully relaxed state. This is the total relaxation. Difference spectra can then be used to get at the extra-atomic relaxation. Comparison with the values of extra-atomic relaxation arrived at via other methods shows that this method yields comparable results. Investigation of the extra-atomic relaxation energy by means of the Auger parameter was found to yield information on the nature of electronegativity. Quantitative and qualitative comparisons of the relative values of extra-atomic relaxation as well as of initial-state effects (chemical shifts) lead to conclusions that are in excellent accord with chemical experience. The correlation between core-ionization potentials and gas-phase acidities breaks down for certain compounds. It was found that the failure arises from the inability of certain aromatic compounds to undergo the same geometric rearrangent upon protonation as their aliphatic analogs. Other experiments into the nature of the dipole of C1F have indicated that, contrary to chemical intuititon and theoretical evidence, the negative end of the dipole may be on the chlorine atom. An investigation of the charge distribution, corrected for relaxation effects, shows that this conclusion is not supported and that the more recent experimental results are correct. An attempt was made to measure the difference between the core-ionization energy of a diatomic molecule and a monatomic dissociation product. While difficulties in experimental procedure made it impossible to measure the core-ionization energy of the atom, an estimate of the magnitude of the relative extra-atomic energy was made.