A. Miczaika

Refractive scattering and the nuclear rainbow in the interaction of12, 13C with12C at 20MeV/N

The elastic and inelastic scattering and the neutron transfer have been measured for the systems12C +12C and13C +12C at 20MeV/N up to θcm= 60° with theQ3D -spectrometer. The angular distributions of the elastic scattering show an enhanced cross section at angles larger than 40°. It can be identified as refractive scattering with the clear signature of a nuclear rainbow.L-cut-off calculations show that these contributions come fromL-values which are significantly lower than the grazingL-value. The deflection function has a broad minimum in thisL-range which is typical for rainbow scattering. TheS-matrix is decomposed by a phenomenological parametrization into a refractive and a diffractive part. The interference of these amplitudes plays an important role in the rainbow enhancement. The spatial localization of the refractive scattering is deduced from the turning points of the corresponding trajectories; a localization between 2.5 fm and 4 fm is found. Semi-classical calculations with complex trajectories in the single-turning-point approximation show good agreement with the quantummechanical calculations. Refractive contributions are not observed in the inelastic scattering. This can be explained by reducing the strength of the conventional collective form factor in the internal region. In contrast to this the enhancement at large angles is seen in the one-neutron transfer channels where the refractive scattering is dominant. This is the first observation of such contributions to heavy-ion transfer reactions.

Heavy ion charge exchange reactions to probe the giant electric isovector modes in nuclei

Abstract The ( 13 C, 13 N) reaction has been studied at E / A = 50 MeV/u on 12 C, 40 Ca, and 58 Ni targets at extremely forward angles including zero degree. Strong excitation of the ΔT z = + 1 analog of the giant dipole resonance is observed, and its angular distribution measured over the range 0° θ lab

Electric isovector nuclear response from 13C induced charge-exchange reactions

Abstract The reaction ( 13 C, 13 N) has been studied at 50 MeV/u on a set of nuclear targets including 12 C, 40 Ca, 58,60 Ni, 90 Zr, 120 Sn and 208 Pb. Excitation of ΔT 2 = 1 giant dipole resonance has been observed in light nuclei ( A ⩽ 60) and corresponding angular distribution have been measured. A broad structure is observed at excitation energy above the GDR in nuclei with A ⩾ 60. Angular-distribution measurements of elastic-scattering cross sections are also reported on 12 C and 58 Ni, as well as excitation of low-lying states in 12 B. Microscopic DWBA analysis of the results is presented. Some results on the ( 13 C, 13 B) reaction are also presented.

The mechanism of the (12C,12N) charge exchange reaction on 12C between 30 and 100 MEV/U

Abstract The Charge exchange reaction 12 C( 12 C, 12 N) 12 B has been studied at 30 and 70 MeV/u in order to investigate the energy dependence of the two reaction mechanisms involved: the direct charge exchange and the proton-neutron exchange. Microscopic calculations have been performed for both processes and an almost quantitative description of the data could be achieved. The p-n exchange is strong at low energies and has a maximum at about 30 MeV/u. The direct process dominates for all states only at energies well above 100 MeV/u, but the energy region for the transition from two-step to direct dominance is strongly state dependent.

Proton stripping induced by 13C at 50 MeV/nucleon on 12C, 40Ca and 58Ni

Abstract The ( 13 C, 12 B) reaction has been investigated at an incident energy of 50 MeV/u on 12 C, 40 Ca and 58 Ni using a magnetic spectrometer. The angular range measured covers the 0° beam direction. Angular distributions of discrete states as well as of structures in the continuum have been measured. They are compared with DWBA calculations. The absolute value of the cross section for the 12 C target is well reproduced, whereas for 40 Ca and 58 Ni discrepancies of a factor 10 are observed.

Transfer and fragmentation reactions of14N at 60 MeV/u

Inclusive energy spectra and cross sections of reaction products close to the14N projectile (11C,12C,13C,15N and15O) have been measured in the angular rangeθL =1.2°–4.2° at an incident energy of 60 MeV/u for five different target nuclei (12C,27Al,58Ni,90Zr and208Pb). Two components are found to be systematically present in the energy spectra of the carbon isotopes, the first similar to that observed at relativistic energies and the second shifted down in energy characteristic for a very dissipative process. The dependence of the differential and integrated cross sections on the target mass indicates that the two-body final channels (14N,13C), (14N,15N) and (14N,15O) are strongly correlated to the fragmentation channels.

Mass measurement and spectroscopy of57Cu with the58Ni(14N,15C)-reaction

The mass of57Cu has been measured with the58Ni(14N,15C)-reaction at 150 MeV incident energy with theQ 3D-spectrometer. The reaction has been selected after a careful inspection of the DWBA-expression for the cross section with respect to the highest weighting factors for spins andl-transfer. Cross sections of several μb/sr have been obtained. TheQ-value has been measured to beQ0=−19.90 (4) MeV and the57Cu mass excess is −47 340 (40) keV. Four lines of excited states have been observed up to 5.7 MeV. These states have a structure of single particle character, since57Cu consists of a doubly closed core with N=Z=28 and a proton outside, and states up to the 2d 5-shell are observed.

SELECTIVITY OF THE (13C, 13N), (13C, 13B) AND (12C, 12N) REACTIONS AT 30 MeV/n

Charge exchange reactions induced by 12C and 13C are discussed on a 12C target nucleus. Comparison of cross sections for the population of dicrete states and of the continuum gives information which determines the selectivity of these reactions with respect to various modes with and without spin-flip.