Absolute measurement of the elastic scattering cross section reaction on oxygen

Resonant scattering cross sections are currently used for light elements backscattering spectroscopy. Many studies of the ¹⁶O(alpha,alpha)¹⁶O reaction cross section, particularly focused on the peak at E_R=3.045 MeV, have been made: results are in disagreement. The very high stability of energy of the Tandetron accelerator ALTAÏS from the LARN laboratory allows a reliable measurement of this cross section.

Thin tantalum coatings have been deposited by magnetron sputtering on a light carbon substrate, in order to isolate the oxygen signal from any background signal. These layers have been anodically oxidized under constant current conditions. Two Ta₂O₅ standards were produced: a thin oxide layer (~4 keV energy loss) for resonances probing, and a thicker layer (~12keV energy loss) to scan the regions where the cross section shows slow variations.

Cross section was measured for energies between 2.4 and 6.0 MeV, at typical backscattering angles 165° and 170°. The main resonance was fixed at E_R=3031.7 keV. Deviations from previous measurements have been observed at high energies.

In order to check the performance of the ¹⁶O(alpha,alpha)¹⁶O reaction for oxygen analysis, multilayers TTiO₂/Si, TiN/Si, TiO₂/TiN/Si, TiN/TiO₂/Si, TiO₂/C samples, and a sample of vaporised functionalized nanotubes were characterised. Advantages of the technique in case of low oxygen concentrations have been pointed out.