Nuclear level density and γ -ray strength function of Ni63

Abstract

The nuclear level density (NLD) and γ -ray strength function (γ SF) of 63 Ni have been investigated using the Oslo method. The extracted NLD is compared with previous measurements using particle evaporation and those found from neutron resonance spacing. The γ SF was found to feature a strong low-energy enhancement that could be explained as M1 strength based on large-scale shell model calculations. Comparison of γ SFs measured with the Oslo method for various Ni isotopes reveals systematic changes to the strength below 5 MeV with increasing mass.

Photon strength functions and nuclear level densities: invaluable input for nucleosynthesis

“…The 66 Ni(n, γ ) cross section was constrained from PSF and NLD measurements on 67 Ni using the inverse Oslo Method [20] with radioactive 66 Ni beams. Simulations demonstrate that the 66 Ni(n, γ ) reaction acts as a bottleneck when using a simplified one-zone model but its impact on i-process nucleosynthesis is negligible in realistic multi-zone low-metallicity AGB stellar models [16].…”

“…The normalization of the transmission coefficients is achieved with the average total radiative width Γ γ of neutron resonances [15], facilitating their conversion into the absolute value of the PSF, which encompasses both E ⁢ 1 and M ⁢ 1 contributions. In cases where Γ γ is not readily available, systematics can be employed as substitutes from suitable mass regions, neighbouring nuclei or models, refer e.g [16–18]. The functional form of the PSF is closely linked to the slope of the NLD which will be discussed in §2b.…”

“…Recent advancements have expanded the frontiers of the Oslo method to allow investigations of the PSFs in neutron-rich nuclei or for nuclei at or near stability where chemical or physical properties of isotopes make manufacturing targets challenging. This is achieved through the analysis of γ -ray data in total absorption spectroscopy following beta-decay, known as the beta-Oslo method [19], or through the utilization of inverse kinematic reactions with stable [20] and radioactive ion beams [16]. Importantly, these innovative experimental approaches all utilize the construction of E x versus E γ matrices, forming the foundation for the application of the Oslo method despite the varying excitation-energy resolutions for the different methods with full widths at half maximum ranging from approximately ± 0.07 to 1 MeV.…”

Uncertainties of nuclear level density estimated using Bayesian neural networks*

“…In recent years, several groups have demonstrated how BNNs can obtain accurate models for predicting nuclear charge radii [17], atomic nucleus mass [18], half-life of decay [19], and fission yield [20], with the uncertainties. In addition, nucleon density distributions are calculated based on the deep neural network method [21][22][23], and level density parameters are estimated using an artificial neural network (ANN) [24] and feedback neural network (FNN) [25].…”

A Comparison between Ericson's Formulae Results and Experimental Data Using New Formulae of Single Particle Level Density

“…Level density is considered an important parameter in many theoretical studies like astrophysical studies and cross-section calculations reaction rates calculations [1][2][3][4][5] .…”