G. Graw

On the isospin anomaly in (d, p) excitation curves from A = 88–106 targets

Abstract For the target nuclei 88 Sr, 90 Zr, 91 Zr, 92 Mo and 106 Cd excitation curves of the (d, p) reaction have been measured with vector polarized deuterons for the transfer of a d f 5 2 neutron. The deuteron energy range covers the region of an anomaly that originates from isospin coupling to the 3p neutron single particle resonance at the emission threshold. The data are reproduced using a DWBA calculation, where the amplitudes of the outgoing p 3 2 and p 1 2 proton partial waves are modified by a resonance term. The analysis confirms the interpretation of the anomaly as an exit channel phenomenon and indicates a decrease of the 3 p 3 2 and an increase of the 3 p 1 2 resonance strength with increasing mass number A .

On the separation of the direct reaction contribution in fluctuating cross sections by the use of polarized particles

Abstract A method to determine the direct reaction contribution y D to the differential cross section in the presence of Ericson fluctuations is proposed. For the scattering of polarized spin - 1 2 particles from spinless nuclei the statistical analysis of the differential cross section dσ/dΩ and of the differential analyzing power ( d σ/ d Ω)A allows an unambiguous and model independent extraction of y D . The method is applied to the elastic scattering of polarized protons from 26 Mg, 88 Sr and 90 Zr; the results are in agreement with Hauser-Feshbach calculations.

Particle-hole and particle-particle correlations in neodymium isotopes

Abstract Excited states in 140, 142, 144, 146 Nd nuclei, up to an excitation energy of about 5 MeV, were investigated by (p,t) experiments performed with a good energy resolution. These data, together with proton and deuteron scattering data from a previous experiment, are compared with Quasi-Particle Phonon Model evaluations, in which the competition between particle-hole and particle-particle residual interactions is considered. The B (Eλ) distributions are satisfactorily reproduced. The 146, 148 Nd(p,t) reaction data are well accounted for, while difficulties are found in reproducing those for 142, 144 Nd(p,t). Limitations and improvements of the model are discussed.

Compound nuclear contributions to the inelastic decay of analog resonances in the 90Zr(p, p′) reacton

Abstract For the 90 Zr ( p , p ′) 90 Zr (2 + , 2.18 MeV ) reaction, the cross section, analyzing power, spinflip probability and spin-flip asymmetry have been measured in the energy region of prominent IAR with J π = 3 2 + near the (p, n) threshold. In the analysis both the direct and the compound nuclear reaction mechanisms are included, the latter in the formulation of Hofmann, Richert, Tepel and Weidenmuller where contributions from channel correlations and width fluctuation corrections are included. In this parametrization we obtain a good reproduction of all the data; the decay widths of the resonances agree well with a weak coupling estimate.

Hyperdeformation and clustering in the actinide region

The excitation energy spectrum of fission resonances has been measured with high energy resolution using the 235U(d,pf) reaction in order to study hyperdeformed (HD) rotational bands and HD nuclear shapes. The moments of inertia of the rotational bands and the energy of the ground state in the third minimum were determined. Another signature of these highly deformed states, their enhanced α decay, was also observed. By studying cold or compact fission in the 232Th(n,f) reaction around HD resonances, we obtained data for heavy clustering.

Hyperdeformed States in the Third Minimum of the Fission Potential

The fission probability and the angular distribution of the associated fission fragments have been measured for the235U(d, pf)236U reaction slightly above the top of the inner fission barrier with the aim of disclosing new hyperdeformed states lying in the third minimum of the fission potential. The results are analyzed together with the data obtained from the literature for234U. The experimental resonances are interpreted as being rotational bands with rotational parameters of ħ/2Θ=1.6±0.6 and 1.8±0,8 keV for234U and236U, respectively. TheK=1, 2 and 4 values of the resonances suggest that these rotational bands are built on some higher-lying excited states in the third minimum of the potential well.

Investigation of the Isospin Threshold Anomaly in (d,p) Reactions with Polarized Deuterons

A systematic investigation of the isospin threshold anomaly in the excitation curves of the vector analyzing power of (,p) reactions has been performed with several target nuclei in the A ≈ 90 and A ≈ 110 mau reglpn. Pronounced effects have been found fpr the (,po) reactions on 88Sr, 90Zr, 92Mo and for the (,p2) rection on 91Zr, whereas the effects for the (,po)reactions on 106Cd, 107Ag and 108Pd are rather small.