Elsevier

Nuclear Physics A

Volume 501, Issue 1, 11 September 1989, Pages 18-50
Nuclear Physics A

89Y + n resonances for E = 10–740 keV and intermediate structure

https://doi.org/10.1016/0375-9474(89)90563-0Get rights and content

Abstract

High-resolution neutron total-cross-section measurements on 89Y have been made from a few eV to 1 MeV using the pulsed neutron time-of-flight spectroscopy at ORELA with a neutron burst width of 5 ns and a nominal resolution of 0.025 ns/m at the highest energy. We have analyzed the data from 10–740 keV using a multilevel R-matrix code and obtained the values of resonance parameters (E0, Jπ, gΓn). From these results we have obtained the values of average quantities up to about 600 keV: Dl = 0 = 4.6 ± 0.3 keV, Dl = 1 = 1.35 ± 0.15 keV; S0 = 0.33 ± 0.045, S1 = 5.82 ± 0.38, in units of 10−4 eV12. The staircase plots of reduced neutron widths for s- and p-waves and the plots of the Lorentz-weighted strength functions averaged over different energy intervals show an evidence of several doorway states. A least-squares fit to the lorentzian smooth curves provides the best values of Ed (doorway energy) and γ2dc (escape reduced width of doorway). These values are in qualitative agreement with the theoretical predictions. The experimental ratio of s- to p-wave level spacings was found to be 3.43 ± 0.6. This is in disagreement with the theoretical prediction of 2.06 (for σ = 3.8) and indicates a parity dependence of the level density at high excitation.

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    Present address: G.B. Pant University, Pantnagar-263145, India.

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