J.J. Kraushaar

Study of the 90Zr(3He, t) reaction

Abstract Differential cross sections were measured for the 90Zr(3He, t)90Nb reaction at 377 MeV. The ground state analogue of 90Zr and some low-lying natural parity (i.e., even J, even parity) states were adequately described by a conventional microscopic DWBA analysis with ( g 9 2 ) p 1 ( g 9 2 ) n −1 orbitals although the interaction strengths were found to increase with increasing J For the unnatural parity states with T = 4 we found the same discrepancy between theory and experiment as was pointed out in the case of 54Fe(3He, t)54Co studies, viz the microscopic reaction model with central forces predicts that the cross section is dominated by orbital angular momentum transfer L = J −1 while the data is better described by L = J + 1 However, good fits were obtained for the states of 1+ at 2 12 MeV and 3+ at 0 65 MeV by including tensor force in the effective interaction The results indicate that the tensor force is quite important f for exciting these odd-spin states

The 96Zr(p, p′) and 96Zr(p, d) reaction at 19.4 MeV

Abstract Elastic and inelastic scattering measurements with 19.4 MeV protons from 96Zr have been performed. The angular distributions for seven inelastic proton groups have been compared to distorted wave calculations using both collective and shell-model form factors. Angular distributions for 11 deuteron groups were measured and compared to distorted wave calculations using a local, zero-range theory. Pick-up of 2 d 5 2 , 1 g 9 2 and 3 s 1 2 neutrons was observed and spectroscopic factors determined.

Study of isobaric analog ground states for several nuclei using the (3He, t) reaction

Abstract The ( 3 He, t) reaction was used at 37.7 MeV to investigate the isobaric analogs of the ground states of 46 Ti, 54 Fe, 62 Ni, 64 Ni, 89 Y, 90 Zr, 91 Zr, 92 Zr and 93 Nb. Differential cross sections were measured from 5° to 50°. The angular distributions were described adequately by a macroscopic distorted wave theory. The effect of variations in the optical-model parameters and in the form of the interaction potential was investigated. The strengths of the interaction potentials extracted from the data are compared with values of the asymmetry potential obtained from a recent analysis of 3 He and t elastic scattering data. Certain nucleus dependent effects are noted. Coulomb displacement energies were determined for nuclei with A around 90.

Study of the effective two-body force using the 54Fe(3He, t) charge exchange reaction☆

Abstract Differential cross sections were measured for the 54Fe(3He, t)54Co reaction at 37.5 MeV. The T = 1 states are well described using a conventional microscopic DWBA analysis with ( f 7 2 ) −2 orbitals but similar analysis of the T = 0 states indicates a serious discrepancy between theoey and experiment.

Excitation of core coupled states in 87Sr and 89Sr via two-step processes in the 88Sr(p, d) and 88Sr(d, p) reactions☆

Abstract The excitation of core coupled states in 87Sr and 89Sr in single-neutron transfer reactions was investigated using the 88Sr(p, d)87Si and 88Sr(d, p)89Sr reactions at Ep = 27.1 MeV and Ed = 17.5 MeV with a resolution of about 18 keV. Angular distributions for states up to an excitation energy of about 3 MeV were obtained from 2°–80° in the (p, d) experiment and 4°–95° in the (d, p) experiment. DWBA calculations were performed and l-values and spectroscopic factors extracted for those states having a single-hole or single-particle character. The excitation of the so-called non-stripping states, originating from the coupling of a 1g 9 2 neutron hole or a 2 d 5 2 . neutron particle to the 2+ or 3− excited states of the 88Sr core were described by two-step calculations involving inelastic excitation of the core and transfer of a neutron. Very good agreement both in shape and magnitude between experimental and calculated angular distributions is obtained both for states excited only through a two-step mechanism and for states where a small direct excitation is allowed. In the latter case the extracted amplitudes for the direct transition agree with model calculations.

A study of the excited states of 57Ni via the (p, d) AND (3He, α) reactions at 27.5 and 37.7 MeV

Abstract The excited states of the 57 Ni nucleus have been studied using the neutron pick-up reactions 58 Ni(p, d) 57 Ni and 58 Ni( 3 He, α) 57 Ni at energies of 27.5 and 37.7 MeV respectively. Recently reported levels at 2.45, 3.01 and 3.36 MeV are confirmed and new levels are reported at 4.46, 4.71, 5.86, 8.24 and 8.79 MeV. Spectroscopic factors and l n , J and T assignments are made for most levels. Previously unreported l n = 0 and 2 levels are discussed.

Spectroscopy of states in 91Zr from γ-ray transitions observed in the 88Sr(α, nγ)91Zr reaction

Abstract Levels below an excitation energy of 3.1 MeV in 91Zr and 3.6 MeV in 90Zr were studied through the prompt γ-radiation in the 87, 88Sr(α, nγ)90, 91Zr reactions. Gamma-ray spectra were recorded in a 25 cm3 Ge(Li) detector at 90° to the beam using 87, 88SrCO3 targets and α-particle energies of 10.3 – 13.5 MeV. The γ-rays observed for transitions in 90Zr are consistent with the known level structure, although some more accurate energy values were measured. In 91Zr, a higher level density was observed in the 2.0 – 3.1 MeV region than had previously been revealed by charged particle reaction experiments. Spins for some of these states are suggested by comparing the variations in γ-ray yields with α-particle energy with Hauer-Feshbach calculations. A new level scheme is proposed for 91Zr which suggests that some previous interpretations of the low-lying states in terms of simple vector-coupled states of the 2d5/2 neutron with 2+ and 3− core states of 90Zr may need to be modified.

A study of the 58Ni, 90Zr and 208Pb(p, d) reactions at 121 MeV☆

Abstract The (p, d) reaction has been studied on 58Ni, 90Zr and 208Pb at 121 MeV in order to test the applicability of the usual DWBA methods to higher energy data. The calculations describe the angular distribution for the strongly excited low-lying states reasonably well when adiabatic-deuteron optical potentials are used. Some discrepancies in shape persist, however, and some values of the spectroscopic factors differ from lower energy data in spite of many variations in the calculations. By use of exact finite-range calculations a value of D02 = 1.23 × 104 MeV2 · fm3 was found for use at 121 MeV. Deuteron D-state contributions were negligible at forward angles and two-step contributions do not appear more significant than for data at lower energy.

A study of the 106Pd(p, d)105Pd and 106Pd(3He, d)107Ag reactions

Abstract The 106 Pd(p, d) 105 Pd reaction has been studied at 22.9 MeV with an energy resolution of 13 keV. Angular distributions permitted the assignment of l -values and the extraction of spectroscopic factors for 13 states including several previously unresolved l = 2 transitions. The 106 Pd( 3 He, d) 107 Ag reaction has also been studied at 32.8 MeV with a resolution of 20 keV. Angular distributions were obtained, l -values assigned and spectroscopic factors extracted for 14 levels including many not observed previously in a proton transfer reaction. The level structure of 105 Pd and 107 Ag is discussed particularly in terms of quasirotational bands.

The decay of 32Cl and 40Sc and the T=1 isobaric analogue states in 32S and 40Ca

Abstract Gamma rays following the decay of 0.30 sec32Cl and 0.18 sec 40Sc have been studied, using NaI scintillation counters and a lithium-drifted germanium detector. Seven gamma rays were identified, both in the case of 32Cl and 40Sc. By the construction of decay schemes through the help of coincidence studies, the positions of the lowest T=1 isobaric analogue states were determined to be at 7.014±0.010 MeV in 32 S and 7.646±0.009 MeV in 40 Ca . The end-point energy of the positon branch to the 2.24 MeV level in 32S was determined to be 9.46±0.09 MeV, and the branch to the 4.48 MeV level in 40Ca to be 9.10±0.09 MeV.