Calculation of energy-loss straggling of C, Al, Si, and Cu for fast H, He, and Li ions
- Instituto de Astronomia y Fisica del Espacio, Casilla de correo 67, Sucursal 28, 1428 Buenos Aires (Argentina)
We present theoretical calculations of the energy-loss straggling of C, Al, Si, and Cu targets for H, He, and Li ions in the range of intermediate to high energies (0.01-10 MeV/u). These calculations have been done by employing the dielectric formalism and by considering the different equilibrium charge states of the swift ion inside the solid as a function of its energy. Two different models are used: the Mermin energy-loss functions combined with generalized oscillator strengths (MELF-GOS) and the shellwise application of the local plasma approximation (SLPA). The MELF-GOS describes the target outer-electron excitations through a fitting to experimental data in the optical limit, employing a linear combination of Mermin-type energy-loss functions; the excitations of the inner-shell electrons are taken into account by means of generalized oscillator strengths. The SLPA employs a free-electron-gas model for the target valence electrons and the local density approximation for each shell of target electrons separately by using Hartree-Fock atomic wave functions. The results of the energy-loss straggling obtained by the two independent models show good agreement with the available experimental data. The calculated energy-loss straggling tends at high energies to the Bohr value and takes values below it at intermediate energies. The Bethe-Livingston shoulder (or overshooting) at intermediate energies does not appear in the present calculations. We find that the energy-loss straggling normalized to Z{sub P}{sup 2} is almost independent of the ion atomic number Z{sub P}; therefore, the results for H, He, and Li projectiles in each target can be approximated by a universal curve at high energies.
- OSTI ID:
- 20982137
- Journal Information:
- Physical Review. A, Vol. 75, Issue 2; Other Information: DOI: 10.1103/PhysRevA.75.022903; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALUMINIUM
ATOMIC IONS
CARBON
CHARGE STATES
COMPUTER CALCULATIONS
COPPER
DENSITY FUNCTIONAL METHOD
ELECTRON GAS
ENERGY LOSSES
EXCITED STATES
HARTREE-FOCK METHOD
HELIUM IONS
HYDROGEN IONS
ION-ATOM COLLISIONS
KEV RANGE
LITHIUM IONS
MEV RANGE 01-10
OSCILLATOR STRENGTHS
SILICON
WAVE FUNCTIONS