Resonant neutron capture in 40Ca

Abstract

The neutron capture cross section of 40Ca has been measured with ≈ 0.2 % energy resolution below E n = 300 keV. Resonance parameters have been extracted for many new p- and d-wave resonances. Gamma-ray spectra were also measured following capture in one doublet and two resolved resonances below 50 keV. Strong feeding of low-lying p-wave levels was observed in all cases. Calculations showed that valence transitions were inadequate to account for the observed dominance of these transitions and a further mechanism is required. The average resonance parameters obtained from the data are as follows: 〈 D〉 = 37 + 4keV, 10 4 S 1 = 0.16 ± 0.05, 10 4 S 2 = 2.0 ± 0.7. The average radiative widths and standard deviations of their distributions were found to be strongly l-dependent as follows: 〈 Γ γ 〉 s = 1.5 ± 0.9 eV, 〈 Γ γ 〉 p = 0.36 ± 0.09 eV and 〈 Γ γ 〉 d = 0.7 ± 0.4 eV.