C{sup 6+}-impact ionization of helium in the perpendicular plane: Ionization to the ground state, excitation-ionization, and relativistic effects

Journal Article · Wed Sep 15 04:00:00 EDT 2010 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.82.032702· OSTI ID:21450554

McGovern, M; Walters, H R. J. ^[1]; Whelan, Colm T ^[2]

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1. Department of Applied Mathematics and Theoretical Physics, Queen's University, Belfast BT7 1NN (United Kingdom)
2. Department of Physics, Old Dominion University, Norfolk, Virginia 23529-0116 (United States)

In search of the discrepancy between theory and experiment in perpendicular plane geometry for C{sup 6+} ionization of He at 100 MeV/amu, we have used the first and second Born approximations to examine whether ionization to an excited He{sup +} state could be significant, whether relativistic effects could be important, and whether there is substantive sensitivity to the He wave functions used in the calculations. We fail to find any explanation of the discrepancy. Of the three possibilities, only relativistic effects turn out to be significant but then only in changing the overall normalization of the cross section, not in changing its shape, which is a prerequisite to getting agreement with experiment. The second Born calculations are in excellent accord with previous impact parameter coupled pseudostate results [Phys. Rev. A 81, 042704 (2010)] and confirm, yet again, that elastic scattering of the projectile by the target nucleus cannot explain the discrepancy. The calculations are extended to the lower impact energy of 2 MeV/amu. Here, in perpendicular plane geometry, ionization to excited He{sup +} states becomes significant and we find an interesting ''oscillatory'' structure in both the ground- and excited-state cross sections. Comparison is made with some relative experimental data and, although the agreement is poor, possibly because of the need to include experimental resolutions, there are nuances in the data that mirror the structures in the calculations.

• OSTI ID: 21450554
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 3 Vol. 82; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
APPROXIMATIONS
BORN APPROXIMATION
CALCULATION METHODS
CARBON IONS
CHARGED PARTICLES
COMPARATIVE EVALUATIONS
CROSS SECTIONS
ELASTIC SCATTERING
ELEMENTS
ENERGY LEVELS
ENERGY RANGE
ENERGY-LEVEL TRANSITIONS
EVALUATION
EXCITATION
EXCITED STATES
FLUIDS
FUNCTIONS
GASES
GROUND STATES
HELIUM
HELIUM IONS
IMPACT PARAMETER
IONIZATION
IONS
MEV RANGE
MULTICHARGED IONS
NONMETALS
RARE GASES
RELATIVISTIC RANGE
RESOLUTION
SCATTERING
SENSITIVITY
WAVE FUNCTIONS