STRONG MATRIX EFFECT IN LOW-ENERGY HE-SCATTERING FROM CARBON( ION)

In low-energy ion scattering the contribution of neutralization proces ses to the scattered ion yield is very important in quantification. Ne utralization of low-energy (1-3.5 keV) He+ ions by carbon is found to be much stronger for graphitic than for carbidic carbon. The ion fract ion for graphitic carbon for 2.5 keV He-3+ scattering over 136-degrees is about 60 times lower than that for carbidic carbon. For the He-4isotope the effect is even larger. Such a strong matrix effect for one element has not been measured before in low-energy (1-3.5 keV) inert- gas ion scattering. The neutralization behaviour is discussed in terms of a special quasi-resonant neutralization process for graphite.