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Phys. Rev. A 68, 064901 (2003) [4 pages]

Experimental energy loss of slow H+ and H2+ in channeling conditions

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J. E. Valdés* and C. Parra
Laboratorio de Colisiones Atómicas, Departamento de Física, Universidad de Santiago de Chile, Casilla 307, Santiago, Chile
Departamento de Física, Universidad Federico Santa María, Casilla 110-V, Valparaíso, Chile

J. Díaz-Valdés
Departamento de Física, Universidad de Concepción, Casilla 160-C, Correo 3, Concepción, Chile

C. D. Denton
Departamento de Física, Universidad Federico Santa María, Casilla 110-V, Valparaíso, Chile

C. Agurto and F. Ortega
Laboratorio de Colisiones Atómicas, Departamento de Física, Universidad de Santiago de Chile, Casilla 307, Santiago, Chile

N. R. Arista
División Colisiones Atómicas, Centro Atómico Bariloche, Instituto Balseiro, S.C. de Bariloche, Argentina

P. Vargas
Departamento de Física, Universidad Federico Santa María, Casilla 110-V, Valparaíso, Chile

Received 1 June 2003; published 12 December 2003

The interactions of hydrogen molecular ions (H2+) and protons in the low energy range (E<7.5keV/u) with very thin foils of monocrystalline gold are experimentally studied. Measurements of energy loss distributions of molecular fragments, recombined molecules, and protons channeled in the 100 direction of a monocrystalline gold thin film have been performed. From the energy loss data we determine the stopping power ratio, which shows a significant negative “vicinage effect,” giving a reduced energy loss of molecular fragments and recombined molecules as compared to the energy loss of protons. This effect is more pronounced in the case of detected molecules. Computational simulations, where nonlinear models are included, qualitatively agree with our experimental results and suggest that some pairs of ions travel and emerge from the crystal with appropriate internuclear distances and relative velocities and are able to recombine at the exit.

© 2003 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevA.68.064901
DOI:
10.1103/PhysRevA.68.064901
PACS:
34.50.Bw, 34.50.Fa, 61.85.+p

*Email address: jorge.valdes@fis.utfsm.cl