Measurements and Calculations of the Nuclear Level Density and γ-Strength Function

The goal of this work was to obtain the level density (NLD) and γ-strength function (γSF) of 70Zn. An experiment was performed at the Oslo Cyclotron Laboratory using a beam of 16 MeV protons incident at a foil of 70Zn. The ensuing reaction 70Zn(p, p ′ γ) 70Zn was detected using the detector arrays OSCAR and SiRi, from which unaligned and uncalibrated spectra were obtained. A novel method was developed to automatically align and calibrate the spectra, with the potential for significantly reducing the time spent on data treatment in future experiments. The coincidence matrix of excitation energy versus γ energy was unfolded from which the matrix of primary generation γ-rays were obtained, and the NLD and γSF were from this extracted. Due to the lack of known values for the average resonance spacing and total radiative width, normalizing the NLD had to be done by using the value of NLD of the neighboring 68Zn along with an ad-hoc 30% uncertainty, while normalizing the γSF by making it fit to data of the giant electric dipole resonance at higher energies. Shell model calculations were performed using the code KSHELL to compute the level scheme and transitions for 70Zn using 100 levels of both parities for spins J ∈ [0, 14]. The NLD and the M 1 component of the γSF were from this computed and compared to the experimental values, along with external data on the E1 component from QRPA. The agreement was good for the NLD, while the M 1+E1 was substantially lower than the experimental γSF at low energies. The latter is believed to be due to underestimation of the E1 strength. A significant low energy enhancement is seen in both the experimental γSF and the computed M 1 component, in agreement with earlier research. The Python package OMpy was developed in collaboration to easier perform the different steps of the Oslo method as well as systematically propagate the uncertainties in the method. The uncertainty is propagated partially by generat- ing an ensemble of Poisson perturbated raw coincidence matrices and performing the Oslo method on all of them. The propagation was hindered by the ad-hoc normalization, but a proxy on the final uncertainty was attained by transforming the standard deviation of each ensemble member