The reflection of low energy helium atoms from tungsten surfaces

The computer program MARLOWE (Version 11.5) has been used to simulate the reflection of 8 eV to 1.5 keV helium atoms from monocrystalline, polycrystalline, and amorphous targets of tungsten. The results are compared with recent experiments of van Gorkum and Kornelsen on (001) targets and of Seidman, et al., on (011) targets. The comparisons of calculated and measured ion ranges indicate that the electronic stopping cross section of low energy helium atoms in tungsten is significantly greater than the traditional LSS value. The reflection coefficients calculated for the (001) surface are in fair agreement with experiment. (orig.)