Direct Measurement of Neutron Transmission Coefficients

Abstract

ever, that a judicious mixture, with some quadrupole radiation would yield satisfactory results.Of the methods used to predict the number and energy of the p rays emitted, the most successful was the equation of Strutinsky. " The assignment of a constant p-ray energy of 1.5 MeV was not successful.Kiefer' found the constant-energy p-ray assumption was adequate in fitting his experimental data. The present work extends to considerably higher excitation energies and it is at high energies that this assumption proves inadequate. The two methods used for assignment of neutron energies predicted approxi-mately the same total de-excitation and the calculation results were in good agreement.

Statistical model calculations for medium and strong absorption in theA=90 region

“…The agreement between . Optical model calculations for s9y, using the parameters of Finckh et al [12,13]. The data are from [36] THW calculations and measurement is good.…”

“…Knowing the spin J and the parity rc of the resonance and of the final states, the transmission coefficients were obtained from the measured decay rates after off-resonance background substraction: This might be the main reason of the discrepancy between the calculated and measured (n, n') cross sections for s9y and 93Nb [20,21]. By modifying the depth and diffuseness of the imaginary potential of [18], Finckh and Jahnke [12,13] were able to generate transmission coefficients in agreement with the experimental ones. Once the optical model parameters for neutrons were established, a careful HF analysis of the off-resonance 91Zr(p, n)91Nb reaction done in [13] confirmed the optical model parameters of Johnson and Kernel [26] as being the most suitable for low energy protons in the A = 90 mass region.…”

“…[22] and references cited therein). Alternatively, in the works [12,13], the neutron transmission coefficients were determined experimentally from the neutron decay of two strong IAR in the 91Zr(p, n)91Nb reaction. Assuming a statistical decay of the IAR [23,24], the neutron branching ratios to different final states are given by the transmission coefficients of the partial waves I, j consistent with angular momentum and parity conservation.…”

“…In order this comparison to be relevant, reliable transmission coefficients should be used in the calculation. Such transmission coefficients were experimentally determined by Finckh and his coworkers [12,13] from an analysis of the 91Zr(p, n)9aNb reaction via isobaric analogue resonances (IAR). In the present work we used the corresponding optical model parameters given by these authors.…”