Electron stimulated ion desorption (ESID) and degradation studies of polypyrrole doped with dodecylsulfate (PPy/DS) deposited on FTO were performed using time-of-flight mass spectrometry (TOF-MS) for ion analysis. The results suggest a strong contribution from fragments of the dodecylsulfate hydrocarbon chain to the mass spectra. In the 650-1500 eV energy range the ion yield curves show maxima at about 600, 1200 and 1400 eV, which can be related to carbon, nitrogen and oxygen-containing fragments, respectively, and interpreted in terms of the Auger Stimulated Ion Desorption (ASID) mechanism. Degradation studies indicate rapid loss of heavier hydrocarbons and an increase of bulk and substrate fragments. Some degradation profiles suggest formation of new species.

Photon stimulated ion desorption (PSID) from condensed carbon dioxide has been studied for photon excitation energies ranging from 93 to 193 eV. PSID studies have been performed at the Brazilian synchrotron light source (LNLS), Campinas, during a multi-bunch operation mode of the storage ring. The results showed that after photon excitation several ions desorbed from the CO2 films: C+ , O+ , CO+ and O2+. PSID experiments showed that ion desorption was enhanced only at the Si resonance excitations. When the thickness of the CO2 was ~ 500 L or higher, almost no desorption yield was observed. The study of the dependence of the relative partial ion yield on the photon excitation showed that the X-ray induced Electron Stimulated Desorption (XESD) mechanism has to be invoked to explain the origin of the desorbed ions in the energy region studied.

O espectro NEXAFS do naftaleno foi analisado sob a aproximação do estado final. Cálculos ROHF/SCF foram realizados para os estados localizados do caroço, segundo o procedimento de Bagus-Schaffer para cada canal de excitação. Cálculos CI foram realizados com excitações simples e duplas do carbono 1s para os dez orbitais virtuais de menor energia. As energias e forças do oscilador foram calculadas e o espectro final foi gerado por convolução de picos gaussianos com 0,5 eV de largura a meia altura, com ponderação estatística dos canais. Os resultados teóricos mostram excelente concordância com o espectro NEXAFS de alta resolução, obtido no BESSY II. Trabalho se encontra em andamento de modo a controlar de maneira adequada o problema do colapso variacional em nível CI através da metodologia MEG-CI, desenvolvida para o tratamento de estados de simetria quebrada. Esta metodologia oferece uma forma clara e transparente de considerar o problema da relaxação, da energia de correlação e da especificidade orbital necessária para o problema da predição do espectro NEXAFS de compostos poliaromáticos.

The near-edge X-ray absorption fine structure (NEXAFS) spectrum of naphthalene was analysed theoratically using the final state approximation rule. ROHF/SCF calculations were carried out for a localized core-hole cationic state under the Bagus-Schaffer scheme for each channel of inequivalent excitations. CI calculations were performed allowing single and double excitations from carbon 1s electrons to the first ten virtual orbitals. The energies and oscillator strengths were calculated. The final spectrum was generated by convolution of Gaussian peaks with 0.5 eV as FWHM of the statistically-averaged calculated transitions. The theoretical result shows remarkable agreement with the experimental high-resolution NEXAFS data measured at BESSY II. Work is in progress to get better control of the variational wave function collapse problem at CI level through the use of symmetry breaking core-hole excited states (MEG-CI). This methodology might offer a clear and transparent way to take into account the relaxational and correlation energy, the virtual orbital specificity and the required restricted configuration interaction needed to the NEXAFS prediction problem.