THE ABSOLUTE YIELD, ANGULAR-DISTRIBUTION AND RESONANCE WIDTHS OF THE 6.13, 6.92 AND 7.12 MEV PHOTONS FROM THE 340.5 KEV RESONANCE OF THE F-19(P,ALPHA-GAMMA)O-16 REACTION

Although the low lying resonances in the F-19(p,alpha-gamma)O-16 reaction have been studied by many investigators in the past, only a few absolute determinations of the gamma-ray yield and branching ratios have been made. This is somewhat surprising in view of the widespread use of this reaction for the quantitative microanalysis of fluorine concentration profiles in the near surface regions of materials and for the calibration of gamma-ray detectors. In this work we report an absolute measurement of the yield, angular distribution and resonance widths of the 6.13, 6.92 and 7.12 MeV photons from the 340.5 keV resonance of the F-19(p,alpha-gamma)O-16 reaction. Photons were produced by bombarding a semithick target of CaF2 with protons from the Harwell 6 MV Van de Graaff accelerator. A 113 cm3 HPGe spectrometer, with an energy resolution of 6.8 keV at 6129 keV, was used as the photon detector. This detector had previously been calibrated absolutely using a combination of radionuclide and thermal neutron capture gamma-ray sources at the neutron facility Badger, adjacent to the Harwell reactor DIDO. Measurements were made at seven angles in the range 0-degrees-150-degrees permitting both differential and integral cross-sections to be derived. Geometrical correction factors were calculated using the Monte Carlo code EGS-4. A value for the reaction width was determined from the excitation curve. With conventional notation the principal results are as follows: gamma-1:gamma-2:gamma-3 = 0.9701:0.0033:0.0266; GAMMA-CM = (2.08 +/- 0.13) keV; and Y(gamma-1) = (8.72 +/- 0.37) x 10(4) 6129 keV gamma-mu-C-1.