Applicability of Modified Effective-Range Theory to positron-atom and positron-molecule scattering

We analyze low-energy scattering of positrons on Ar atoms and N2 molecules using Modified Effective-Range Theory (MERT) developped by O'Malley, Spruch and Rosenberg [Journal of Math. Phys. 2, 491 (1961)]. We use formulation of MERT based on exact solutions of Schroedinger equation with polarization potential rather than low-energy expansions of phase shifts into momentum series. We show that MERT describes well experimental data, provided that effective-range expansion is performed both for s- and p-wave scattering, which dominate in the considered regime of positron energies (0.4 - 2 eV). We estimate the values of the s-wave scattering lenght and the effective range for e+ - Ar and e+ - N2 collisions.Comment: RevTeX, 4 pages, 2 figure

Il constante progredire della frontiera tra teologia e scienza. Parte 2º: Metafisica

On constant movement of frontiers between Science and Theology. Part 2: Metaphysics In the first part (Karwasz, Scientia et Fides, 3(1) 2015) entitled “Physics” we showed how discoveries of modern sciences do not contradict Bible: neither in the subject of the beginning of the word nor in the subjects of the homogeneity of Homo Sapiens and the common origin of Euroasiatic languages. In this part we show that numerous “explanations” of natural phenomena like Pauli’s exclusion principle governing the chemistry, like space-time of Einstein, like apparent paradoxes of quantum mechanics, in reality move the border of our knowledge towards metaphysics: writings of philosophers from Aristotle, S. Augustine, S. Thomas to Kant are not in contrast with ontological conclusions of modern physics. In this way, the explanations based on philosophical principles find their place in natural sciences

Decoration of Buried Surfaces in Si detected by Positron Annihilation Spectroscopy

The terminations of buried surfaces of two different cavity types (nano- and microcavities) produced in the same He+-H+ co-implanted p-type Si (100) sample annealed at 900 °C, are studied and characterized by positron annihilation spectroscopy. The characterization was carried out by means of three complementary positron techniques: Doppler broadening and coincidence-Doppler broadening spectroscopy with a continuous slow positron beam, and lifetime spectroscopy with a pulsed slow positron beam. It was found that the nanocavities have a pristine surface of Si, while the surfaces of the microcavities, formed below protruding blisters, are oxygen decorated. This case study opens the interesting use of the positron spectroscopy tool in the topical subject of empty space for microelectronics applications.Fil: Brusa, R.S.. Universita degli Studi di Trento; ItaliaFil: Macchi, Carlos Eugenio. Universita degli Studi di Trento; Italia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; ArgentinaFil: Mariazzi, S.. Universita degli Studi di Trento; ItaliaFil: Karwasz, G.P.. Universita degli Studi di Trento; ItaliaFil: Egger, W.. Universität der Bundeswehr München; AlemaniaFil: Sperr, P.. Universität der Bundeswehr München; AlemaniaFil: Kögel, G.. Universität der Bundeswehr München; Alemani

Multi-channel analog of the effective-range expansion

Similarly to the standard effective range expansion that is done near the threshold energy, we obtain a generalized power-series expansion of the multi-channel Jost-matrix that can be done near an arbitrary point on the Riemann surface of the energy within the domain of its analyticity. In order to do this, we analytically factorize its momentum dependencies at all the branching points on the Riemann surface. The remaining single-valued matrix functions of the energy are then expanded in the power-series near an arbitrary point in the domain of the complex energy plane where it is analytic. A systematic and accurate procedure has been developed for calculating the expansion coefficients. This means that near an arbitrary point in the domain of physically interesting complex energies it is possible to obtain a semi-analytic expression for the Jost-matrix (and therefore for the S-matrix) and use it, for example, to locate the spectral points (bound and resonant states) as the S-matrix poles.Comment: 33 pages, 10 figure

Plasma–liquid interactions: a review and roadmap

Plasma–liquid interactions represent a growing interdisciplinary area of research involving plasma science, fluid dynamics, heat and mass transfer, photolysis, multiphase chemistry and aerosol science. This review provides an assessment of the state-of-the-art of this multidisciplinary area and identifies the key research challenges. The developments in diagnostics, modeling and further extensions of cross section and reaction rate databases that are necessary to address these challenges are discussed. The review focusses on non-equilibrium plasmas