Light Mass Nuclei Research Articles

Nuclear structure studies of double Gamow-Teller and double beta decay strength

The double Gamow-Teller strength distribution is evaluated microscopically in a series of light and medium mass nuclei using the shell model approach. The specific 2β decay transition from the ground state to ground state is computed in all the nuclei considered and the model dependence of the result is studied. The importance of the coherence when summing over the intermediate states is studied and is found to be a crucial factor in most of the double Gamow-Teller transitions. The effects of SU(4) symmetry breaking are studied using several models and types of interactions. This breaking is much larger in medium mass nuclei ( A = 44) than in the lighter nuclei ( A = 8, 12, or 20). The behaviour of double Gamow-Teller ground state to ground state transition amplitudes on the size of the model space is found to be complicated and to be different for different nuclei. The probabilities of studying double Gamow-Teller strength in combined ( p, n) and ( n, p) experiment, in pion double charge-exchange, and charge-exchange reactions are discussed.

The influence of water absorption in samples for neutron capture cross section measurements

Sample-related corrections for average neutron capture cross section measurements are complicated in the keV region due to the resonance structure. In particular, light mass nuclei present in chemical compounds of rare earth materials make corrections for neutron multiple-scattering and self-shielding difficult. Moreover, samples of chemical compounds such as oxides are hygroscopic. A Monte Carlo method has been developed by taking into account the effects caused by neutron slowing down into the resonance region due to the scattering from hydrogen and oxygen atoms. The validity of the calculated corrections has been investigated by comparing experimental data of oxide and metallic samples. The calculation method and related problems will be discussed.

Measurement of the average cross sections for ( n, p) reactions on some light and medium mass nuclei in the 241 AmBe neutron spectrum

Measurement of the average cross sections for ( n, p) reactions on some light and medium mass nuclei in the 241 AmBe neutron spectrum

Effective two-body forces in light and medium mass nuclei

From the spectroscopic information provided by single particle stripping reactions, we have extracted average effective two-body interaction between nucleons in thep-, sd-, andfp- shells. Using the derived interaction parameters, we have calculated the energy centroids of the level spectra of residual nuclei obtained via single nucleon stripping reactions involving light and medium mass nuclei as targets.

The (p,d) reaction at intermediate beam energies. I. Plane-wave Born approximation (semi-analytical) calculations

Plane-wave Born approximation calculations have been carried out for the (p,d) reaction at intermediate beam energies with the purpose of elucidating the manner in which the various physical parameters of the problem determine the behaviour of the cross-sections. Analytical formulae for the differential cross section are derived for three choices of the bound state wave function: square well, Woods–Saxon, and truncated harmonic oscillator. The formulae can essentially be factored into two parts, one which oscillates rapidly with momentum transfer q(and is not physically important) and the other which varies smoothly with q and describes the 'envelope' of the calculated angular distribution. For the square well and truncated harmonic oscillator form factors, this envelope function varies as q−8 and q−10 respectively, but in the Woods–Saxon case it is given predominantly by an exponential q-dependence. To illustrate our main points, calculations are presented for the 208Pb(p,d) reaction, primarily at 200 MeV, as well as normalized fits to presently available data at 185 MeV on light and intermediate mass nuclei and at 700 MeV on 12C. The envelope dependence of the square well and Woods–Saxon form factors gives a reasonably good account of these data.

Cross-Section Requirements for Charged-Particle Fusion Reactors: The 6Li(p,3He)α Reaction

Absolute cross-section measurements for reactions among light-mass nuclei (A < 10) are important in feasibility studies of controlled thermonuclear reactor systems. For a 6Li-d fueled fusion reactor, the 6Li (p,3He)α reaction is of particular interest. The absolute cross sections for this reaction are incomplete and poorly known and have accordingly been remeasured in the range Ep = 3 to 12 MeV. The results support recent measurements below 3 MeV in finding the cross section to be higher in this region than previously supposed. Additional results for the 6Li(p,p)6Li and 6Li(p,p′)6Li* reactions imply the cross sections for these reactions are ∼40% higher than earlier measurements. A plot of the Maxwell-averaged reaction rate parameter, , for the 6Li(p,3He)α reaction is presented as a function of kT, the temperature of a p – 6Li plasma.