Energy loss versus exit angle for H+ and He+ ions channeled in Au <100> at very low energies, and observation of a molecular effect for incident H2 +

E. A. FIGUEROA; E. D. CANTERO; J. C. ECKARDT; G. H. LANTSCHNER; M. L. MARTIARENA; N. R. ARISTA

PHYSICAL REVIEW A - ATOMIC, MOLECULAR AND OPTICAL PHYSICS

AMER PHYSICAL SOC

Año: 2008 vol. 78 p. 329011 - 329019

1050-2947

The variation of the energy loss versus the exit angle in channeling experiments using H+, He+, and H+ fragments produced by the incidence of H2+ on thin gold crystals oriented in the <100> direction has been investigated in the low-velocity range, corresponding to energies below 10 keV/u. The experimental results for H+ and He+ were compared with computational simulations performed with the MARLOWE code, considering an impact-parameter-dependent energy loss based on electron density calculations and low-energy stopping power models. The comparisons provide information on the impact-parameter dependence of the energy loss for channeled ions and serve as a test of theoretical models in the present low-energy range. A molecular effect isobserved for the transmitted H+ fragments corresponding to H2+ incidence. This effect is explained based on geometrical considerations and a vicinage effect in the energy loss of correlated protons.