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Title: State-Specified Protonium Formation in Low-Energy Antiproton-Hydrogen-Atom Collisions

Abstract

We calculate state-specified protonium-formation cross sections in low-energy antiproton-hydrogen-atom collisions by solving the Chew-Goldberger-type integral equation directly instead of integrating the traditional differential scattering equation. Separating the incident wave from the total wave function, we calculate only the scattered outgoing wave propagated by the Green function. The scattering boundary condition is hence automatically satisfied without the tedious procedure of adjusting the wave function at the asymptotic region. The formed protonium atoms tend to be distributed in higher angular momentum l and higher principle quantum number n states as the collision energy increases. The present method has the advantage over the traditional ones in the sense that the required memory size and the computational time are much smaller, and accordingly the problem can be solved with higher accuracy.

Authors:
;  [1];  [2];  [1]
  1. Institute of Materials Science, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan)
  2. (Japan)
Publication Date:
OSTI Identifier:
20861481
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 97; Journal Issue: 24; Other Information: DOI: 10.1103/PhysRevLett.97.243202; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ANGULAR MOMENTUM; ANTIPROTONS; ATOM COLLISIONS; BOUNDARY CONDITIONS; CROSS SECTIONS; GREEN FUNCTION; HYDROGEN; INTEGRAL EQUATIONS; PROTONIUM; SCATTERING; WAVE FUNCTIONS

Citation Formats

Tong, X. M., Hino, K., Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, and Toshima, N.. State-Specified Protonium Formation in Low-Energy Antiproton-Hydrogen-Atom Collisions. United States: N. p., 2006. Web. doi:10.1103/PHYSREVLETT.97.243202.
Tong, X. M., Hino, K., Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, & Toshima, N.. State-Specified Protonium Formation in Low-Energy Antiproton-Hydrogen-Atom Collisions. United States. doi:10.1103/PHYSREVLETT.97.243202.
Tong, X. M., Hino, K., Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, and Toshima, N.. Fri . "State-Specified Protonium Formation in Low-Energy Antiproton-Hydrogen-Atom Collisions". United States. doi:10.1103/PHYSREVLETT.97.243202.
@article{osti_20861481,
title = {State-Specified Protonium Formation in Low-Energy Antiproton-Hydrogen-Atom Collisions},
author = {Tong, X. M. and Hino, K. and Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 and Toshima, N.},
abstractNote = {We calculate state-specified protonium-formation cross sections in low-energy antiproton-hydrogen-atom collisions by solving the Chew-Goldberger-type integral equation directly instead of integrating the traditional differential scattering equation. Separating the incident wave from the total wave function, we calculate only the scattered outgoing wave propagated by the Green function. The scattering boundary condition is hence automatically satisfied without the tedious procedure of adjusting the wave function at the asymptotic region. The formed protonium atoms tend to be distributed in higher angular momentum l and higher principle quantum number n states as the collision energy increases. The present method has the advantage over the traditional ones in the sense that the required memory size and the computational time are much smaller, and accordingly the problem can be solved with higher accuracy.},
doi = {10.1103/PHYSREVLETT.97.243202},
journal = {Physical Review Letters},
number = 24,
volume = 97,
place = {United States},
year = {Fri Dec 15 00:00:00 EST 2006},
month = {Fri Dec 15 00:00:00 EST 2006}
}
  • Expressions for momentum distributions of electrons in antiproton-hydrogen-atom collisions are derived in the framework of the advanced adiabatic approach for the time- independent Schroedinger equation. Protonium formation cross sections for states with different n and l spherical quantum numbers are also obtained. Total ionization and protonium formation cross sections are compared with other calculations in the interval of impact energies from 0.5 eV to 10 keV. We show that diabatic states promoted into the continuum can be rigorously defined within the advanced adiabatic framework.
  • In a departure from our previous work modeling antiproton capture on helium, with its relatively straightforward, fixed center target, extending the semiclassical approach to molecular hydrogen, a multicenter target with target masses identical to the projectile, requires that we reconsider the fundamental nature of our model, in particular the momentum-dependent Heisenberg core used to stabilize electrons in the ground state. Here we discuss the main features of our Kirschbaum-Wilets model of molecular hydrogen as it is calibrated against proton collision data, and then used to study antiproton collisions. Details of the collision process are presented, including the energy and angularmore » momentum states of incident antiprotons that result in formation of pp, and the resulting distribution of protonium atomic states.« less
  • A quantum-classical hybrid (or semiclassical) method is applied to protonium formation p+H{sub 2}{sup +}{yields}pp+H and dissociation p+H{sub 2}{sup +}{yields}p+p+H at kinetic energies up to 200 eV. The electronic motion is accurately solved quantum mechanically, while the motion of the heavy particles p and p is described by classical mechanics. The p-p-p collinear configuration is assumed as a preliminary to three-dimensional calculations, and to assess the validity of the adiabatic approximation. Vibrational excitation to the dissociative continuum is crucial in pp formation in contrast to the importance of electron emission for the atomic-hydrogen target. For this reason, pp formation occurs efficientlymore » even well beyond the ionization threshold if the target is a molecule.« less
  • Single and multiple ionization of neon and argon atoms by 3.6 MeV/u Au{sup 53+} impact has been explored in kinematically complete experiments. Doubly differential cross sections for low-energy electron emission have been obtained for a defined charge state of the recoiling target ion and the receding projectile. Observed target specific structures in the electron continuum are attributable to the nodal structure of the initial bound state momentum distribution. The experimental data are in excellent accord with continuum-distorted-wave eikonal-initial-state single ionization calculations if multiple ionization is considered appropriately. (c) 1999 The American Physical Society.
  • Cross sections for formation of protonium (pp-bar) in low-energy collisions of antiprotons with hydrogen atoms (H) and negative hydrogen ions (H ) are calculated using the classical-trajectory Monte Carlo (CTMC) method. Full four-body dynamics is performed for p-bar+H . Previously unpredicted differences between p-bar+H and p-bar+H collisions, stemming from the dynamics of the weakly bound electron in H , are exhibited. A maximum protonium formation cross section of nearly 2 AS for p-bar+H is found, smaller than previous theoretical estimates, but the reaction window is found to extend to higher energies. The electron stripping cross section for p-bar+H collisions ismore » also calculated and yields results in agreement with our previous three-body CTMC calculation and with a very recent experimental determination. The implications of these results for experiments with corotating beams of p-bar and H are discussed.« less