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Fluorine, one of the lightest elements in nature, is a chemically reactive element that is used in many technological and industrial applications. Natural fluorine is monoisotopic, with one stable isotope, 19F. It can be found in a wide variety of materials such as batteries, metals, polymers, ceramics, geological and biological samples. These characteristics render fluorine especially important for detection and depth profile determination via Ion Beam Analysis (IBA) techniques.
The most appropriate of such techniques, in analyzing the majority of light elements, is the proton-Elastic Backscattering Spectroscopy (p-EBS), since protons can reach greater depths than other ion beams for the same energy/nucleon values. In order to achieve greater sensitivity to the near-surface layers of a sample, the p-EBS technique is implemented at Ep,lab=100 keV-300 keV (Medium Energy Ion Scattering – MEIS), due to the increase of the corresponding stopping power values. Adding to this, the fact that the differential cross section of the proton elastic scattering on 19F presents resonances even below 1 MeV, further increases the detection limits of the isotope and offers higher accuracy of the corresponding concentration depth profile. Consequently, in order to apply the p-EBS technique, in the medium energy range, reliable differential cross sections are needed. The experimental cross-section data are also of significant importance for the extension of the theoretically evaluated datasets well below 0.5 MeV.
The experiment took place at the 4 MV Dynamitron Tandem Laboratory of the Central Unit for Ion and Radionuclides (RUBION) of the Ruhr University Bochum in Germany. A 500 kV single-stage accelerator and a 4 MV Dynamitron Tandem accelerator were used for the measurements, which provided protons of Ep,lab=100 keV-340 keV and Ep,lab=300 keV-1000 keV, respectively. The 19F(p,p0)19F elastic scattering was studied at five backscattering detection angles. The obtained cross-section data were followed by R-matrix calculations [1], for the reproduction of the experimental values. The final results are compared to the existing datasets from the literature as well as the current evaluation [2].
[1] R. E. Azuma et al., “AZURE: An 𝑅-matrix code for nuclear astrophysics,” Phys. Rev. C, vol. 81, no. 4, p. 045805, Apr. 2010, doi: 10.1103/PhysRevC.81.045805.
[2] A. F. Gurbich, “SigmaCalc recent development and present status of the evaluated cross-sections for IBA,” Nucl. Instruments Methods Phys. Res. Sect. B Beam Interact. with Mater. Atoms, vol. 371, pp. 27–32, Mar. 2016, doi: 10.1016/j.nimb.2015.09.035.