Fernando J. da Paixao

Electron-impact excitation of H2: minimal orbital basis for single configuration interaction

We report theoretical differential excitation cross sections for scattering of electrons by H2 molecules using the Schwinger multichannel approach (SMC). This study differs from previous applications of the SMC method in the description of the excited states (which are now obtained through the single configuration interaction technique) and in the level of the multichannel coupling. The calculation is performed with singlet and triplet states present in the manifold. The results given by this strategy show a significant improvement to experimental data in comparison with earlier two-state close coupling calculations.

Cross sections for electron-impact excitation of the H2 molecule using the MOB-SCI strategy

In this paper, we report integral and differential cross sections for the electronic excitation of H2 molecules by electron-impact. Our scattering amplitudes were calculated using the Schwinger multichannel method within the minimal orbital basis for single configuration interactions (MOB-SCI) level of approximation. Through the use of the present strategy we have investigated the coupling effects among ground state and first singlet and triplet states of the same spatial symmetry. The five-state (nine for degenerated states) close-coupling calculations joined the advantages of a well-described set of physical states of interest with a minimum associated pseudo-state space. The results obtained by means of the MOB-SCI technique show a significant improvement towards experimental data in comparison with previous two-channel close-coupling calculations.

Elastic differential cross sections for electron collision with CF3 and CF3H

We report theoretical differential elastic cross sections for scattering of electrons by CF3 radical (trifluoromethyl or carbon trifluoride) and CF3H (fluoroform). The calculations were performed with the Schwinger multichannel method at the static-exchange level. Our results for CF3 are the first cross sections for open-shell molecules with nonlinear geometry. There is no experimental data for e--CF3 scattering but the theoretical data for CF3H are in good agreement with recent experimental results of Tanaka. Our results show interesting similarities between elastic cross sections of e--CF3 and e--CF3H scattering.

Immobilization and photoacoustic spectroscopy of N-(2-pyridyl)acetamide cation complexes bonded to silica gel

N-(2-Pyridyl)acetamide was covalently immobilized onto silica gel giving 1.57 × 10–4 mol of this molecule per gram of silica. This new bidentate chelate extracts MCl2(M = Ni, Co, Cu) from ethanol and acetone solutions. The photoacoustic spectra of the solid complexed samples were obtained in the visible and near-infrared spectral regions and were analysed using ligand field theory. The calculated Racah parameters indicate a tetrahedral geometry for nickel and cobalt and a highly distorted octahedral geometry for the copper complex.

Photoacoustic spectroscopy of a diacetamide copper complex immobilized on silica gel

Abstract Silica gel-immobilized diacetamide is very effective in extracting copper(II) from ethanol or acetone solutions. The complex formed on the surface was studied by means of photoacoustic spectroscope. The IR and visible spectra gave clear evidence that the cation is octahedrally coordinated with a strong tetragonal distortion.