The energy-level structure of a pair of electron and positron confined in a quasi-one-dimensional nano-scale potential well has been investigated focusing on its trend in the small limit of confinement strength ω, namely, the Wigner molecular regime. An anisotropic Gaussian-type basis functions supplemented by high angular momentum functions as large as l = 19 has been used to obtain reliable f...

The positron emitter Mn (t1/2 5 46.2 min, Iβ1 5 97%) is of potential interest in positron emission tomography (PET). With a view to optimizing its production route, excitation functions for deuteron induced nuclear reactions on isotopically enriched (,95%) Cr were determined radiochemically over the energy range of 3 to 13 MeV and for proton induced nuclear reactions on Cr in the range of 18 to...

Electron-molecule collisions play a crucial role in astrophysical environments where the electron fraction is higher than about 10−5, e.g. in the diffuse ISM, PDRs or comets. We present here a brief review of our recent R-matrix calculations of rate coefficients for electron-impact rotational excitation of interstellar molecules. Our major result is the prediction of emission lines from higher ...

introduction range and diffusion of positron-emitting radiopharmaceuticals are important parameters for image resolution in positron emission tomography (pet). in this study, geant4 toolkit was applied to study positron diffusion in soft tissues with and without a magnetic field for six commonly used isotopes in pet imaging including 11c, 13n, 15o, 18f, 68ga, and 82rb. materials and methods gea...

We study 1s→2s(2p) excitation of hydrogen as a function of the nuclear charge of the projectile, ZP , for a fixed impact velocity, v51.3 a.u., for which electron excitation, capture, and ionization are competitive processes. For this purpose, we have performed large ab initio close-coupling calculations using a molecular basis in the framework of the impact-parameter method. Excitation probabil...

Rotational excitation of H2O, HDO and D2O by thermal electron impact is studied using the molecular R-matrix method. Rate coefficients are obtained up to electron temperatures of 8000 K. De-excitation rates and critical electron densities are also given. It is shown that the dominant transitions are those for which J = 0, ±1, as predicted by the dipolar Born approximation. However, a pure Born ...

We report a very detailed test of the ab initio discrete momentum representation (DMR) method of calculating vibrational excitation of polyatomic molecules by electron impact, by comparison of its results with an extensive set of experimental data, covering the entire range of scattering angles from 10° to 180° and electron energies from 0.4 to 20 eV. The DMR calculations were carried out by so...

Experimental and calculated differential cross sections DCSs for electron-impact excitation of the 010 bending mode and unresolved 100 symmetric and 001 antisymmetric stretching modes of water are presented. Measurements are reported at incident energies of 1–100 eV and scattering angles of 10° –130° and are normalized to the elastic-scattering DCSs for water determined earlier by our group. Th...