The total cross section of the 12 C+ 16 O fusion reaction has been measured at low energies to investigate the role of this reaction during late stellar evolution burning phases. A high-intensity oxygen beam, produced by the 5MV pelletron accelerator at the University of Notre Dame, impinged on a thick, ultra-pure graphite target. Protons and γ-rays were simultaneously measured in the center-of-mass energy range from 3.64 to 5.01 MeV for singles and from 3.73 to 4.84 MeV for coincidence events, using silicon and Ge detectors. Statistical model calculations were employed to interpret the experimental results. The emergence of a new resonance like broad structure and a decreasing trend in the S-factor data towards lower energies (opposite to previous data) are found for the 12 C+ 16 O fusion reaction. Based on these results the uncertainty range of the reaction rate within the temperature range of late stellar burning environments is being discussed .

Excited states of 133 La have been investigated to search for the wobbling excitation mode in the low-spin regime. Wobbling bands with nω = 0 and 1 are identified along with the interconnecting ∆I = 1, E2 transitions, which are regarded as one of the characteristic features of the wobbling motion. An increase in wobbling frequency with spin implies longitudinal wobbling for 133 La, in contrast with the case of transverse wobbling observed in 135 Pr. This is the first observation of a longitudinal wobbling band in nuclei. The experimental observations are accounted for by calculations using the quasiparticle-triaxial-rotor (QTR) model, which attribute the appearance of longitudinal wobbling to the early alignment of a π = + proton pair.

Experimental measurements of evaporation residue (ER) cross sections for the 19 F + 194,196,198 Pt reactions forming 213,215,217 Fr compound nuclei are reported. The cross sections are measured at beam energies in the range of 101-137.3 MeV. The survival probability of the 213 Fr compound nucleus with neutron number N = 126 is found to be lower than the survival probabilities of 215 Fr and 217 Fr with neutron numbers N = 128 and 130 respectively. Statistical model analysis of the ER cross sections show that an excitation energy dependent scaling of the finite-range rotating liquid drop model fission barrier is necessary to fit the experimental data. The fitted scaling factors for 213 Fr are found to be smaller than those of 215 Fr and 217 Fr for almost the entire range of excitation energies.

No abstract

No abstract