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Register a new userScattering processes in antiprotonic hydrogen - hydrogen atom collisions
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The elastic scattering, Stark transitions and Coulomb deexcitation of excited antiprotonic hydrogen atom in collisions with hydrogenic atom have been studied in the framework of the fully quantum-mechanical close-coupling method for the first time. The total cross sections $sigma_{nl to nl}(E)$ and averaged on the initial angular momentum $l$ cross sections $sigma_{nto n}(E)$ have been calculated for the initial states of $(bar{p}p)_{n}$ atoms with the principal quantum number $n=3 - 14 $ and at the relative energies $E=0.05 - 50$ eV. The energy shifts of the $ns$ states due to the strong interaction and relativistic effects are taken into account. Some of our results are compared with the semiclassical calculations.
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Predictions of cross sections and analyzing powers using g-folding optical potentials for the scattering of 71A MeV 6,8He ions from (polarized) hydrogen are compared with data. A g-folding model in which exchange amplitudes are evaluated explicitly was used with wave functions of 6,8He specified from a no-core shell model that used a complete (0+2+4)hw basis. The analyzing powers reveal some sensitivities to the details of the wave functions, especially in the case of halo nuclei.
The recent and older level shifts and widths in pbar atoms are analyzed. The results are fitted by an antiproton-nucleus optical potential with two basic complex strength parameters. These parameters are related to average S and P wave scattering parameters in the subthreshold energy region. A fair consistency of the X-ray data for all Z values, stopping pbar data and the Nbar-N scattering data has been achieved. The determination of neutron density profiles at the nuclear surface is undertaken, and the determination of the neutron R_{rms} radii is attempted. Uncertainties due to the input data and the procedure are discussed.
We present evidence showing how antiprotonic hydrogen, the quasistable antiproton-proton (pbar-p) bound system, has been synthesized following the interaction of antiprotons with the hydrogen molecular ion (H2+) in a nested Penning trap environment. From a careful analysis of the spatial distributions of antiproton annihilation events, evidence is presented for antiprotonic hydrogen production with sub-eV kinetic energies in states around n=70, and with low angular momenta. The slow antiprotonic hydrogen may be studied using laser spectroscopic techniques.
We investigate the role of hydrogen collisions in NLTE spectral line synthesis, and introduce a new general empirical recipe to determine inelastic charge transfer (CT) and bound-bound hydrogen collisional rates. This recipe is based on fitting the energy functional dependence of published quantum collisional rate coefficients of several neutral elements (BeI, NaI, MgI, AlI, SiI and CaI) using simple polynomial equations. We perform thorough NLTE abundance calculation tests using our method for four different atoms, Na, Mg, Al and Si, for a broad range of stellar parameters. We then compare the results to calculations computed using the published quantum rates for all the corresponding elements. We also compare to results computed using excitation collisional rates via the commonly used Drawin equation for different fudge factors, SH, applied. We demonstrate that our proposed method is able to reproduce the NLTE abundance corrections performed with the quantum rates for different spectral types and metallicities for representative NaI and AlI lines to within $le$0.05 dex and %le%0.03 dex, respectively. For MgI and SiI lines, the method performs better for the cool giants and dwarfs, while larger discrepancies up to 0.2 dex could be obtained for some lines for the subgiants and warm dwarfs. We obtained larger NLTE correction differences between models incorporating Drawin rates relative to the quantum models by up to 0.4 dex. These discrepancies are potentially due to ignoring either or both CT and ionization collisional processes by hydrogen in our Drawin models. Our empirical fitting method performs well in its ability to reproduce, within narrow uncertainties, the abundance corrections computed with models incorporating quantum collisional rates. It could possibly be extended to other transitions or in the absence of published quantum calculations, to other elements as well.
In this paper the N=2 supersymmetric extension of the Schroedinger Hamiltonian with 1/r-potential in arbitrary space-dimensions is constructed. The supersymmetric hydrogen atom admits a conserved Laplace-Runge-Lenz vector which extends the rotational symmetry SO(d) to a hidden SO(d+1) symmetry. This symmetry of the system is used to determine the discrete eigenvalues with their degeneracies and the corresponding bound state wave functions.
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