Single electron ionization of ammonia and methane molecules by swift proton impact

C. A. TACHINO; J. M. MONTI; O. A. FOJÓN; C. CHAMPION; R. D. RIVAROLA

Lanzhou

Conferencia; XXVIII International Conference on Photonic, Electronic and Atomic Collisions; 2013

In the present work, objective is to investigate the influence of the representation of theinitial bound molecular wavefunctions in the single ionization reaction of NH3 and CH4 molecules by proton impact. To this end, double differential cross sections (DDCS) are calculated by employing two different approaches, both within the post and prior version of the CDW-EIS (continuum distorted wave-eikonal initial state) model. In the first approximation, proposed by Senger et al. [1,2], the molecular bound wavefunction is proposed to be a linear combination of atomic orbitals centered on each molecular nucleus. Since in this approximation all the overlap terms are neglected, DDCS for a given molecular orbital is thus reduced to a linear combination of DDCS corresponding to the atomic orbitals of each atomic compound of the molecule, being the corresponding coefficients obtained via a population analysis. In a second approach, we use the self-consistent field approximation description given by Moccia [3-5] for the ground state of XHn-type molecules, where each molecular orbital is expressed as a linear combination of Slater-type functions all centered in the heaviest nucleus of the target. In both cases, the final states are represented by a triple product of the two projectile and target coulomb continuum factors (with different effective target charges) and a plane wave. DDCS as a function of the energy and angle of the emitted electron were calculated for impact of protons on NH3 and CH4 molecules at intermediate and high collision energies. In these calculations, post and prior versions of the transition amplitude were used. In general, a reasonable agreement with experimental data [2] is obtained. Differences can be observed between post and prior results obtained employing the Senger method, being the last one in better agreement with experiments for both backward and forward emission angles.References[1] B Senger et al 1984 Nucl. Instrum. Methods Phys. Res. B 2 204[2] B Senger et al 1988 Z. Phys. D: At., Mol. Clusters 9 79[3] R Moccia 1964 J. Chem. Phys. 40 2164[4] R Moccia 1964 J. Chem. Phys. 40 2176[5] R Moccia 1964 J. Chem. Phys. 40 2186