(n, p) Reaction for Gold

Abstract

The paper reports an experimental study of the process Au 197 (w,£)Pt 197 induced by 14-Mev neutrons, detecting protons in the angular range 10° to 45° with emulsions. Resolution is not adequate for the identification of single excited states, but the energy spectrum does display definite structure and five groups are distinguished, chiefly on the basis of gross differences in their angular distributions. The energy widths of these groups are smaller than expected in view of the target thickness. Positions of angular distribution peaks are utilized for the assignment of angular momentum changes. The corresponding excitations in Pt 197 , with "final angular momentum" parameters and total cross sections, are: 0.2 Mev, 2, 8.6 mb; 1.6 Mev, 0 (or 4), 2.2 mb; 2.9 Mev, 5, 2.0 mb; 4.4 Mev, 6, 5.2 mb; 6.0 Mev, 4 (or 0), 2.5 mb. The sum of these cross sections (20.5 mb) is the experimental value for the reaction cross section, since the ground state transition was probably not observed (cross section estimated not over 0.6 mb) and no significant yield of protons was observed corresponding to Pt excitation between the highest listed and the maximum (13 Mev) represented in the spectrum. All cross sections are subject to about 40% uncertainty in neutron flux, but statistical uncertainties are of order 20% or less. Maximum differential cross sections for the groups, and their locations in the angular distributions, are tabulated.Protons emerging from aluminum foil bombarded by D-f-T neutrons have been studied with 400 p, emulsions recording over a continuous range of angles from 15° to 165°. Groups in the composite energy spectrum correspond to known Mg 27 levels at 1.0 and 3.5 Mev and suggest additional ones at 1.6, 5.7, and 7.0 Mev. The nuclear "temperature'' for the continuous portion of the spectrum is 1.2 Mev. The following cross sections are tabulated: for each energy group, isotropic and anisotropic total cross sections and maximum differential cross section; for all protons over 2 Mev, differential cross sections at 30° intervals. The isotropic component greatly exceeds the forward-peaked one for each group. Total cross section for the reaction is estimated to be 79±15 millibarns.

Nuclear spectrometry of 9.6 h 196Aum2 and the reaction of 197Au with fast neutrons

“…From table 12, a cross section for 197 Au(n, p) 197 Pt m at 14.1 MeV of 1.0 mb±25% is inferred. Previous measurements of the 197 Au(n, p) 197 Pt t cross section involved either recoil proton observation [184] or the radiochemical separation of 18.3 h 197 Pt g [159,185], which includes 97% of the precursor decay of shorter-lived 197 Pt m [186]. The J π values for 197 Pt g and 197 Pt m are 1/2 − and 13/2 + , respectively [81].…”