J. Nurzynski

(d, t) reactions on 54Cr, 67, 68Zn nuclei

Abstract Levels in 53Cr, 66, 67Zn have been investigated using the (d, t) reaction at 12 MeV deuteron energy. Angular distributions have been measured and spectroscopic factors obtained from a comparison with the DWBA predictions. A clear j-dependence which could be fitted with DWBA was observed for low-lying ln = 1 transitions in 67Zn. A j-dependence for both ln = 1, 3 transitions in 53Cr was also seen, neither of which could be reproduced by DWBA. Filling coefficients and centre-of-gravity energies were obtained for 68Zn and both compared to the predictions of the simple pairing theory.

Global optical-model analysis of the elastic deuteron scattering from medium heavy target nuclei

Abstract Angular distributions for the cross section and the analyzing powers iT 11 , T 20 , T 21 and T 22 in the angular range 20°–175° (lab) have been measured for 12 MeV deuterons scattered elastically from several medium-heavy, spin-zero target nuclei. The data have been analysed using an optical model including complex spin-orbit and tensor terms. With a few exceptions, excellent fits have been obtained to all the measured quantities, yielding a set of global parameters. The depths of the central part of the optical potentials are correlated and depend on the structure of the target nuclei. Contrary to the results for selenium, which exhibit clear shell-closure effects that are well reproduced by optical-model calculations, the data for N = 28 nuclei were found to be very difficult to describe. Irregularities in the optical-model parameters and problems in fitting the measurements are discussed. Possible ways of improving the theoretical description of deuteron scattering are suggested.

j-dependence of l = 1 transitions in the 54Cr(d, p) 55Cr reaction

Abstract Differential cross sections for six l = 1 transitions in the reaction 54 Cr(d, p) 55 Cr have been measured at a deuteron bombarding energy of 8 MeV. The data have been described qualitatively by DWBA calculations employing spin-orbit terms in the deuteron and proton optical model potentials to reproduce the observed dependence on j . Spin assignments of 3 2 , 1 2 , 3 2 , 1 2 and 1 2 have been made for the ground, 0.245, 0.573, 1.487 and 2.905 MeV states in 55 Cr. The 2 p 1 2 and 2 p 3 2 spectroscopic factor sums were found to be 0.66 and 0.56 respectively indicating a large admixture of (2 p 1 2 ) 2 configurations in the ground state of 54 Cr.

The elastic scattering of 5.5–10.0 MeV 3He particles by 27Al nuclei

Abstract Angular distribution for the elastic scattering of 5.5, 7.0, 8.0, 9.0 and 10.0 MeV 3 He particles by 27 Al nuclei have been measured for scattering angles between 15° and 165° in the laboratory system. The 5.5 MeV results are significantly different from those published by Parry et al. 1 ). The data have been analysed using simple optical model Woods-Saxon potentials.

Reorientation effects for 52 MeV vector polarized deuterons

Abstract The differential cross sections, d σ(θ) d Ω , and the vector analysing powers, iT 11 ( θ ), were measured for the elastic and inelastic scattering of 52 MeV vector polarized douterons from 20 Ne, 22 Ne, 26 Mg, 28 Si, 32 S, 34 S, 36 Ar and 40 Ar nuclei. Coupled channels analysis was carried out using an axially symmetric rotational model with either prolate or oblate quadrupole deformations for each isotope. Calculations assuming harmonic vibrator model were also carried out. In general, reorientation effects were found to be weak. A global optical model potential containing an imaginary spin-orbit component was found to be the most suitable in describing the experimental data at this energy.

Energy dependence of the 24Mg(16O, 12C)28Si reaction

Abstract Excitation functions for the reaction 24 Mg( 16 O, 12 C) 28 Si(g.s., 2 + 1 ) were measured at 5°(lab) in the energy range 32 E c.m. E c.m. = 37.5, 40.2 and 43.5 MeV. Angular distribution measurements at these energies yield spin assignments, from P 2 j (cos θ ) comparisons, of 27, 29 and 31, respectively. Attempts to find a consistent optical-model fit to the elastic scattering in the entrance channel and an exact finite-range DWBA fit to the four-nucleon transfer reaction in this energy range were unsuccessful. Such a failure is to be expected if strong couplings between the elastic channel and inelastic channels of either the initial or final system are important. The features of the resonance phenomena in the transfer reaction are discussed within a band crossing model framework.

The 50, 52, 54Cr(α, p)53, 55, 57Mn reactions at Eα = 18 and 26 MeV

Abstract The 50, 52, 54Cr(α, p)53, 55, 57Mn reactions have been studied at 18 and 26 MeV bombarding energies. From the 26 MeV data angular distributions for 95 levels were obtained, nearly all of which could be described by the DWBA procedure assuming a quasi-triton transfer process. In contrast, at 18 MeV very few angular distributions could be adequately described in this way. Both L = 1 and L = 3 if J-dependence were observed in the (α, p) data by comparing angular distributions for which lp transfer values had previously been determined in single-proton transfer reactions. Many Jπ assignments in 53, 55Mn were made by utilizing this J-dependence. In 57Mn 38 new states (in a total of 57) were observed and tentative Jπ assignments made for many of these states. Two new levels at 6.069 and 6.164 MeV were located in 55Mn and 8 proton unbound states were populated in 53Mn. Large differences were found for the relative strengths of states populated in the (α, p) and (3He, d) reactions. The implications of the data on the (α, p) reaction mechanism and on the nuclear structure are discussed.

The reaction 28Si(3He, α)27Si at E(3He) = 12 MeV

Angular distributions for the Si(3He, 3He)Si and the 28Si(3He, α)27Si reactions induced by 12 MeV 3He particles have been measured. The analysis in terms of the optical model and the DWBA has been carried out and the results are discussed in conjunction with other data for the neutron pick-up reactions from 28Si. Occupation numbers for neutrons in d52, d32 and S12 orbits are obtained for the ground state wave functions of 28Si and compared with the proton occupation numbers.

States in 97, 101Ru observed in the reactions 96,100Ru(d, p)

Abstract The neutron single-particle strength distributions for the nuclei 97 Ru and 101 Ru have been investigated using the (d, p) reaction at a deuteron energy of 11.5 MeV, with an overall experimental resolution of approximately 25 keV. Angular distributions of proton groups leading to sixteen final states in both nuclei were measured in the angular range 15.0 to 67.5°. The measured cross sections are analyzed in the framework of the distorted waves Born approximation to deduce l -values and spectroscopic factors of the states in the residual nuclei. The ground-state Q -value for the 96 Ru(d, p) 97 Ru reaction has been determined to a much improved accuracy, Q 0 = 5.886 ± 0.003 MeV.

The dependence of the spectroscopic factors on parameters of distorting potentials for the reaction 26Mg(τ, α)25Mg

Abstract Angular distributions of α-particles from the reaction 26 Mg(τ, α) 25 Mg studied at E τ = 10.2 MeV have been analysed in terms of DWBA. To avoid the necessity of introducing a lower cut-off radius in the calculation of radial integrals, deep potentials have been used. Changes in the potential of the incident particles are found to have only a small influence on the calculated distributions. The fits to the experimental data can be optimized by readjusting one parameter only, namely the depth of the real part of the optical-model potential for α.-particles. The present analysis indicates that the dependence of the ratio of the spectroscopic factors S ( l , j )/ S g.s. ( l , j ) on the exit channel parameters is weaker (by a factor of from 0.5 to 0.2) than the dependence of the absolute value of the calculated cross sections on the same parameters. The experimental value of the normalization coefficient D 0 2 , obtained here for the (τ, α.) reactions is 22 ± 6.