A High Resolution Study of p + 44Ca Reactions

Abstract

A high resolution measurement of the cross-sections of the 44Ca(p,p0) and 44Ca(p,p1) reactions was performed over the energy range E[subscript p] = 2.50--3.53 MeV to improve the purity and completeness of the 45Sc level sequences. A specific goal was the investigation of possible parity-dependence of the level densities of 45Sc. This research was performed at the High Resolution Laboratory at Triangle Universities Nuclear Laboratory. The data were measured at five angles and the observed cross-sections were fit with the multilevel, multichannel, R-matrix code MULTI6. Many levels were observed for the first time, and many levels were reassigned different quantum numbers. A total of ~800 resonances were observed.

The purity and completeness of the 45Sc data were tested via several statistical analyses: the nearest-neighbor spacing distribution, the reduced width distribution, and the Dyson-Mehta Δ₃ statistic. The results of the statistical analyses were mixed. The s-wave resonance sequence compares very well with random matrix predictions. The other sequences do not agree well with GOE predictions, suggesting missing and/or misassigned levels.

The experimental nearest-neighbor spacings were compared to the Wigner distribution to identify anomalously large (small) spacings which imply missing (misassigned) levels. The number of anomalous spacings has been reduced, indicating improved purity and completeness of the data. In particular the small spacing anomalies proved to be a very useful and practical analysis tool. The level densities were determined using two methods to correct for missing levels. Uncertainties in the level densities have been significantly reduced. No evidence of parity dependence in the level densities of 45Sc was observed.