H recoil cross-sections for 7Li ions at 30° and 45° in the energy interval from 2.28 to 5.70 MeV

Abstract

Elastic recoil detection analysis (ERDA) using a He ion beam and a detector with a stopper foil is a common technique for the analysis of hydrogen and its isotopes. A good alternative to He ERDA, for laboratories not equipped with a He ion source, is the use of Li ions. These may be beneficial because of an increased depth resolution due to the larger stopping power and higher cross-section for hydrogen recoils. Deviations from the Rutherford cross-section at 30° can be expected for energies above 2.9MeV. However, as far as the authors know, ERDA cross-sections for H with Li ions at energies above this critical energy are not available in the literature. Therefore, differential proton recoil cross-sections for incident 7Li ions were measured in this work in an energy range between 2.28 and 5.70MeV at recoil angles of 30° and 45°. Thin melamine foils (∼50μg/cm2) evaporated on thin Al (∼50μg/cm2) backings were used for the measurements. Special care was taken to monitor hydrogen loss during the measurement.