MULTIPLE-SCATTERING X-RAY-ABSORPTION ANALYSIS OF SIMPLE BROMINATED HYDROCARBON MOLECULES

A multiple-scattering analysis of Br K-edge extended X-ray absorption spectra of some brominated hydrocarbon molecules is presented. A new m ethod for calculating multiple-scattering contributions and to perform data analysis has been used. The brominated hydrocarbons solubilized in different molecular assemblies and macromolecular systems may be us ed as probe molecules. An accurate analysis of the intramolecular cont ribution to the absorption spectra allows the possibility of identifyi ng the intermolecular contacts related to the systems in which these m olecules are solubilized to be evaluated. We present a very accurate X -ray absorption spectroscopy investigation of several brominated hydro carbons (bromoethane, 2-bromopropane, 2-bromo-2-methylpropane, and bro mobenzene), taking into account the three-body multiple-scattering con tributions which are found to give a detectable signal to the X-ray ab sorption cross-section. The presence of double-electron excitation edg es is reported. The inclusion of these additional edges allowed us to obtain a very good agreement between the calculated and the experiment al spectra and reliable values of interatomic distances. Moreover, mea n values and standard deviations of the bond-angle distributions have been determined. The results indicate that the molecular geometry of t he brominated aromatic hydrocarbons gives rise to a strong multiple-sc attering signal which could compromise the determination of the interm olecular contacts. The aliphatic brominated hydrocarbons seem to be mo re suitable to be used as probe molecules.