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The shake-up features of the N1s and C1s core-level x-ray photoelectron spectra of model molecules of polyaniline are studied theoretically using the intermediate neglect of differential overlap method in combination with configuration interaction. The calculations are performed on N,N’-diphenyl-1,4-phenylenediamine and N,N’-diphenyl-1,4-benzo-quinondiimine, which are model molecules for fully reduced and fully oxidized polyaniline, respectively. The core-level spectra of these two molecules are also studied experimentally by means of x-ray photoelectron spectroscopy. Experimental and theoretical results are found to be in excellent agreement, which allows for a detailed interpretation of the observed shake-up spectra. Core ionization of imine nitrogens is shown to be accompanied by large shake-up intensity. Our studies of model molecules are compared with recently published core-level spectra of polyaniline at various oxidation levels. The increase in imine nitrogen content upon oxidation of the polymer give rise to an increase in the N1s shake-up intensity, a result which is in agreement with what we find for the model molecules. [ABSTRACT FROM AUTHOR]

A semiempirical method, based on INDO (intermediate neglect of differential overlap), is employed to calculate the shake-up spectrum of the C1s peak of benzene. Intensities are computed within the framework of the equivalent-core approximation, including correlation in both final and initial states. The method yields intensity ratios which are better than previously obtained theoretical results and in close agreement with experiment. The factors contributing to the intensity of individual peaks are analyzed and an assignment is proposed for the main features in the experimental spectrum. [ABSTRACT FROM AUTHOR]

The C1s core photoelectron spectra of a series of alkene molecules, ethene, propene, 1-butene, cis and trans 2-butene, 2-methyl-propene, and 1-pentene are discussed. The experimental spectra are assigned using intermediate neglect of differential overlap-configuration interaction (INDO-CI) calculations and comparative discussions. It is shown that hyperconjugation is a useful concept in the assignment of the transitions. INDO-CI is shown to give a reasonable description of the low energy part of the spectra. The results are used in the discussion of molecular models for the interpretation of the electronic structure of polyacetylene. [ABSTRACT FROM AUTHOR]

We investigate the electronic excitation in aniline tetramers at various levels of oxidation and protonation. We show that for certain geometrical conformations there is excellent agreement between our results and recently published experimental data. The neutral forms of the tetramer are shown to have excitation spectra almost identical to polymer equivalents. For the doubly protonated emeraldine tetramer we propose a bipolaron type of defect state, unlike in its polymer equivalent for which a polaronic metal model has been proposed. The electronic transitions associated with the bipolaron are shown to involve only one bipolaron level in contrast to the common picture of two bipolaron levels. [ABSTRACT FROM AUTHOR]

Previously, a geometrical model of the thermochromism in poly(3-alkylthiophene) was proposed, based upon an analysis of optical absorption spectra as well as ultraviolet and x-ray photoelectron spectra (UPS and XPS). In the present contribution, the shake-up features in the XPS C(1s) spectra of thiophene, hexyl-substituted thiophene, and bithiophene molecules in the gas phase, are compared with the shake-up features in previously published XPS C1s spectra of poly(3-hexylthiophene) and poly(3-butylthiophene). An analysis of these gas phase molecular data confirms the geometric model of electronic localization in the polymer materials proposed previously. [ABSTRACT FROM AUTHOR]

Reversible thermochromism in thin solid films of poly(3-hexylthiophene), or P3HT, has been studied using ultraviolet and x-ray photoelectron spectroscopies (UPS and XPS, respectively). The UPS and XPS spectra, as well as previously published optical absorption spectra, are analyzed using the results of valence effective Hamiltonian (VEH) quantum chemical calculations of the electronic structure of isolated polymer chains. The analysis of the spectra indicates that at elevated temperatures thermally induced electronic localization occurs as a consequence of thermally induced conformational disorder. [ABSTRACT FROM AUTHOR]