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Puerto Serrano, Spain

Valdes A.,National University of Colombia | Prosmiti R.,Institute Fisica Fundamental IFF
European Physical Journal D | Year: 2016

Quantum mechanical multiconfiguration time-dependent Hartree (MCTDH) calculations are presented for the Ar2ICl cluster. The Hamiltonian operator is expressed in satellite coordinates, with its potential term being represented as a sum of the three-body ArICl ab initio parameterized interactions plus the Ar-Ar ones. The potential surface shows different type of low-lying minima (global and local), that influence the vibrational dynamics of the system. The vibrational ground state properties and specific vibrationally excited states are obtained from improved relaxation MCTDH calculations employing a large number of basis set functions, especially for the angular part, to achieve convergence. By analyzing the spatial density distributions of the vibrational states we are able to characterize the corresponding states to different isomers, such as tetrahedral, linear, bending type ones. The binding energy of each isomer is also computed, and they contribute to evaluate their relative stability, as well as the importance of the underlying multiple minima of the potential surface. © EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2016.

Machacek J.R.,Australian National University | Blanco F.,Complutense University of Madrid | Garcia G.,Institute Fisica Fundamental IFF | Buckman S.J.,Australian National University | And 2 more authors.
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2016

In an effort to aid the modelling of positron and positronium (Ps) transport in biological media we have compiled recent experimental results for the total Ps formation in positron scattering from atoms and molecules. A simple function was found to adequately describe the total Ps formation cross section for both atoms and molecules. The parameters of this function describe the magnitude and shape of the Ps formation cross section and are compared to physical characteristics of the target atoms and molecules. A general trend in the magnitude of the total Ps formation cross section is observed as a function of the target atom/molecule dipole polarisability. The functional form may enable quick estimation of the Ps cross section for molecules for which experimental measurements or theoretical estimates do not exist. © 2016 IOP Publishing Ltd.

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