Rutherford Backscattering with Heavy Ions

The mass resolution capabilities of heavy ion Rutherford backscattering spectrometry (HIRBS) have been explored. A generalized prediction has been made of the maximum mass resolution that can be obtained in HIRBS. The experimental mass analysis capabilities of three heavy ion beams, 24 MeV 16O, 23 MeV 20Ne, and 38 MeV 40Ar was investigated in detail. Using these beams, a mass difference of 1 amu can be determined at a target mass of 25 amu; a mass difference of 2 amu can be determined at a target mass of 65 amu. For each beam, the energy differences necessary for qualitative and quantitative analysis were determined. For the 16O beam the corresponding experimental values are 250 and 350 keV, respectively, for qualitative and quantitative determination. For the 20Ne beam the values are 275 and 425 keV, for the 40Ar beam the values are 700 and 1200 keV. From these experimental ¿E values the mass resolution achievable with each beam is estimated. HIRBS is potentially capable of resolving neighboring masses for 50 < M < 100 and appears well suited for detecting such species on the surface of low Z substrates.