Absolute hydrogen depth profiling using the resonant ${}^1$H(${}^{15}$N,$\alpha \gamma$)${}^{12}$C nuclear reaction

Abstract

Resonant nuclear reactions are a powerful tool for the determination of the amount and profile of hydrogen in thin layers of material. Usually, this tool requires the use of a standard of well-known composition. The present work, by contrast, deals with standard-less hydrogen depth profiling. This approach requires precise nuclear data, e.g. on the widely used ${}^1$H(${}^{15}$N,$\alpha \gamma$)${}^{12}$C reaction, resonant at 6.4\,MeV ${}^{15}$N beam energy. Here, the strongly anisotropic angular distribution of the emitted $\gamma$-rays from this resonance has been re-measured, resolving a previous discrepancy. Coefficients of (0.38$\pm$0.04) and (0.80$\pm$0.04) have been deduced for the second and fourth order Legendre polynomials, respectively. In addition, the resonance strength has been re-evaluated to (25.0$\pm$1.5)\,eV, 10\% higher than previously reported. A simple working formula for the hydrogen concentration is given for cases with known $\gamma$-ray detection efficiency. Finally, the absolute approach is illustrated using two examples.