[en] Maxwellian Neutron capture cross sections important for nucleosynthesis processes in stars are computed from the recommended individual resonance parameters, as well as from the measured energy dependent cross sections. The experimental neutron capture cross sections, spanning the energy range from a few keV to about 500 keV are evaluated in the framework of the Lane-Lynn capture formalism by including several partial waves in the analysis. In addition, in a few cases, the neutron inelastic scattering channels are included. The feasibility of extrapolating the calculations to nuclides off the stability line is examined. The effect of stellar temperature in the range from 10 keV to 50 keV on the Maxwellian neutron capture cross sections is investigated. The Maxwellian capture cross sections at 30-KeV for ⁹³Nb, ¹²⁷I, ¹⁴¹Pr, ¹⁵⁰Sm, ¹⁵²Sm, ¹⁵⁴Sm, and ¹⁸¹Ta are computed and are compared with other determinations

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[en] The valence and channel neutron model of Lane and Lynn remarkably account for partial radiative widths of neutron resonances in the 3p-giant resonance. Evidence is presented for valence neutron capture at and in the neighborhood of the 3s-giant resonance in target nuclei ³⁶Ar and ⁵⁴Fe. In addition, the variation of the correlation coefficient rho with the reduction power factor n of the γ ray energy is studied. (4 figures, 1 table) (U.S.)

No abstract available

[en] Because of recent advances in experimental techniques, which improved the accuracies of thermal capture and scattering cross sections by an order of magnitude, a more stringent approach in the evaluation of the thermal constants is developed. In the present approach, the following aspects are introduced: (1) a consistency between thermal cross sections, coherent and incoherent scattering lengths, and neutron resonance parameters is achieved; (2) a consistency between the isotopic and element cross sections is sought; in addition, for each isotope, the requirement that the partial cross sections add up to the total is fulfilled; (3) where possible, charged particle data particularly derived from (d,p) reactions on light and medium weight isotopes are used in locating the positions and strengths of bound levels. Such a procedure is useful in the evaluation of the shape of the cross sections in the thermal region; and (4) the Lane-Lynn theory of direct capture is called upon to calculate thermal cross sections and check for consistencies for certain isotopes. Extensive examples to illustrate these procedures are presented

[en] A first observation of two resonance-like structures at mass numbers 92 and 112 in the average capture widths of the p-wave neutron resonances relative to the s-wave component is interpreted in terms of a spin-orbit splitting of the 3p single-particle state into P_3/2 and P_1/2 components at the neutron separation energy. A third structure at about A = 124, which is not correlated with the 3p-wave neutron strength function, is possibly due to the Pygmy Dipole Resonance. Five significant results emerge from this investigation: (i) The strength of the spin-orbit potential of the optical-model is determined as 5.7 ± 0.5 MeV, (ii) Non-statistical effects dominate the p-wave neutron-capture in the mass region A = 85 - 130, (iii) The background magnitude of the p-wave average capture-width relative to that of the s-wave is determined as 0.50 ± 0.05, which is accounted for quantitatively in tenns of the generalized Fermi liquid model of Mughabghab and Dunford, (iv) The p-wave resonances arc partially decoupled from the giant-dipole resonance (GDR), and (v) Gamma-ray transitions, enhanced over the predictions of the GDR, are observed in the ⁹⁰Zr - ⁹⁸Mo and Sn-Ba regions.

[en] Primary E1 transitions due to thermal neutron capture by the nuclides ⁹Be, /sup 32,34/S, /sup 40,42,44,46,48/Ca, and ⁵⁸Ni are quantitatively interpreted by the Lane-Lynn formula and are compared with recent optical model calculations. The two approaches are equivalent provided the internal region of the nucleus is excluded in the optical model approach. Theoretical justifications for such a procedure are briefly presented. 32 refs., 4 tabs

[en] A reanalysis of the ⁹Be(n,γ)¹⁰Be data yields a revised value of 1.25 +- 0.15 MeV for the spin-spin potential, V/sub Iσ/. Other evidence for such a term is derived from ¹⁰B(n,γ)¹¹B where V/sub Iσ/ = 1.6 +- 0.6 MeV. The Lane isovector symmetry potential is determined from ⁴⁸Ca(n,γ)⁴⁹Ca where W/sub D/ = 11.3 - 67.8 ((N - Z)/A) MeV

[en] The resonance parameters and thermal cross sections of ²³⁵²³⁸U and ^239240241242Pu are reevaluated by considering the measurements carried out since 1973. Capture, scattering, fission cross sections as well as resonance integrals are calculated from the parameters and are compared with experimental values with the objective of achieving consistency between calculations and measurements. The Dyson-Metha Δ₃ statistical analysis was applied in order to calculate average level spacings. Calculations of average radiative widths based on systematics are carried out and are compared with experimental values as well as with Moore's and Lynn's estimates

No abstract available