K.R. Cordell

The reaction: High-spin states, resonances and coherence widths

Abstract Excitation functions were measured for states of 21 Ne populated by the 12 C ( 13 C , α) reaction over the bombarding energy range E lab = 18.2–32.0 MeV (18.4–27.0 MeV) at θ lab = 7°(25°) in in 200 keV steps, and average coherence widths of states and the moment of inertia of the compound nucleus 25 Mg were obtained from these excitation functions. A statistical analysis of these data was performed. Angular distributions for states in 21 Ne to 10 MeV in excitation energy were measured at θ lab = 7°, 18°, 28° and 43° at bombarding energies from 29.0 to 31.0 MeV in 400 keV steps. These data along with Hauser-Feshbach predictions allow us to suggest spins for some states as well as to suggest possible candidates for rotational bands in 21 Ne.

Search for resonances in 12C(9Be, α)17O

Abstract Excitation functions at 7° (lab) have been measured from E c.m. = 5.1 to 11.4 MeV in approximately 114 keV steps for 15 groups of final states in 17 O populated by the 12 C( 9 Be, α) reaction. Statistical tests have been used to locate possible non-statistical structure in the excitation functions. Possible anomalies were found near E c.m. = 6.3, 7.5, 8.9 and 9.7 MeV. Angular distributions were measured at E c.m. = 9.20, 9.71 and 10.23 MeV for the three lowest excited states in 17 O. The data have been compared with Hauser-Feshbach calculations in addition to the following reaction mechanisms: compound plus a single resonance, compound plus interfering resonances and compound plus direct reactions.

Resonances: Population of low-level density regions?

Abstract A simple explanation based primarily on the binding energies of nuclei in the entrance channel and level densities calculated with the shell model is proposed to explain the occurence of resonances in heavy-ion reactions for sd-shell nuclei.

Proton-inclusive cross sections from 600 MeV proton-nucleus reactions☆

Abstract Proton-inclusive cross sections were measured for 600 MeV proton bombardment of 27Al and 181Ta targets using the SREL synchrocyclotron. Proton energies were measured with a plastic scintillator time-of-flight system, and a 10.2 cm thick NaI detector was used for particle identification. The results of classical many-body and knock-on calculations are compared with the data.

Proton inclusive cross sections from 720 MeV α-nucleus reactions

Abstract Proton inclusive cross sections have been measured from 30°–150° (lab) for outgoing energies up to 500 MeV from the bombardment of 720 MeV α-particles on Al and Ta. An exhaustive survey of applicable models indicates that the intranuclear cascade and knock-out models provide the best description of the data. Single scattering mechanisms seem to be important, and there is some indirect evidence that high nuclear density effects occur.

Comparison of fusion cross sections for 12C+12C → 24Mg and 14N+10B → 24Mg

Abstract The total fusion cross sections have been measured and compared for two light systems, 12 C + 12 C and 14 N + 10 B, leading to the same compound nucleus at the same excitation energies, E ∗ ( 24 Mg ) = 40, 50, 55 and 60 MeV . The critical angular momenta extracted for the formation of 24 Mg via 12 C + 12 C and 1 14 N + 10 B are different enough to clearly indicate the presence of an entrance channel effect (limitation). The Z -distributions of the evaporation residues are compared to each other and to Hauser-Feshbach calculations. The data are also fitted with and compared to theoretical models which predict total fusion cross sections.