K. Langanke

Neutron blocking in elastic α-scattering on Oxygen isotopes

Abstract Elastic α- 18 O scattering has been studied microscopically within the framework of the generator coordinate method. The bound states of the α- 18 O system agree very well with the 22 Ne ground state band. The scattering phase shifts as well as the bound states show a strong parity splitting. A comparison with the α- 16 O system gives no evidence for a reduction of parity splitting due to the blocking of the 18 O excess neutrons as suggested by Sunkel and Wildermuth.

Microscopic study of the low-energy3He(3He, 2p)4He and3H(3H, 2n)4He fusion cross sections

We have calculated the3He(3He, 2p)4He and3H(3H, 2n)4He reaction cross sections at low energies within the microscopic multichannel resonating group method. For both reactions, we find good agreement with experiment. For the3H(3H, 2n)4He reaction, our calculated energy dependence reproduces that of each individual low-energy experimental data set, except for a normalization constant. Using this fact, we derive at a low-energy3H(3H, 2n)4He rate by taking the averaged mean of these fits.

Microscopic study of elastic 16O28Si scattering

Abstract Elastic 16 Oue5f8 28 Si scattering is studied microscopically within the Generator Coordinate Method. A resonance analysis supplies a series of three rotational bands; the two excited bands agree very well with rotator-like structures found in experiment. The phase shifts do not show any parity dependence.

AstrophysicalS(E) factor of8Li (α,n0)11B and inhomogeneous Big Bang nucleosynthesis

The cross section of the11B(n, α)8Li reaction has been measured atEn=7.6 to 12.6 MeV. The neutron beam was produced via theD(d, n)3He reaction and aBF3 counter (with naturalB isotopic composition) served both as target for the11B nuclides and as detector for the observation of the delayedα-activity of8Li. The data match well with previous results obtained atEn=12.5 to 20.0 MeV. Using the principle of detailed balance the data were converted to the case of the8Li(α, n0)11B reaction. The associated astrophysicalS(E) factor is dominated by a resonance atER=0.58 MeV of widthΓR =200 keV, withS(ER)=8400 MeV b. ThisS (ER) value for the n0 channel alone is already three times higher than the constantS(E) factor assumed previously and, thus, strengthens the significance of inhomogeneous Big Bang nucleosynthesis.

The low-energyD(α, γ)6Li and6Li+208Pb→D+α+208Pb cross sections

We have calculated theE1 andE2 contributions to the low-energyD(α,γ)6Li fusion and to the6Li+208Pb →D+α+208Pb Coulomb dissociation cross sections within a multichannel Resonating Group calculation based on many-body deuteron+α configurations and pseudo-states. For both reactions experimentally determined cross sections are reasonably well reproduced. We find that dipole capture contributes noticeably to the fusion cross sections atE≦500 keV, while it is negligible in the Coulomb dissociation data.

Microscopic study of elastic scattering of almost identical nuclei: The 16O18O system

Abstract Elastic 16Oue5f818O scattering has been studied microscopically using the Generator Coordinate Method. The calculation supports the predictions by LeMere et al. concerning the influence of the core-exchange term.

Monte Carlo simulations of the Lewis effect

Recent experiments measuring the thick-target yield curve of narrow resonances in (p, γ) reactions on23Na,26Mg and27Al nuclei clearly show the Lewis effect. We have studied this effect theoretically on the basis of a Monte Carlo simulation of the nuclear and electronic energy loss curve in the target. We are able to reproduce the experimental data qualitatively. We discuss possible implications of precision measurements of the Lewis effect.

Determination of target surface-properties from high-resolution ion-beam experiments

By analyzing the thick target yield curve of resonant (p,γ) reactions on23Na and26Mg for various target temperatures within a Monte Carlo approach, we are able to define the Debye and Einstein temperature of the target material in the surface region. The obtained surface temperatures are noticeably higher than the respective calorimetric values.