R. Sherr

Coulomb displacement energies in the 1f72 shell

Abstract The experimental data for Coulomb displacement energies in the mass region 33 to 65 are discussed. It is found for isobaric pairs of nuclei for which all nucleons in excess of 40 lie in the 1 f 7 2 shell that ΔE c is with resonable accuracy given by the expression ΔE c = 7220 + 300 (Z > ′ − 1) + (250/2T) [ 1 2 (1 + (−1) Z′ >)] in keV, where Z > ′ = Z > − 20. There is essentially no A -dependence for these nuclei as either N or Z is changed. On the other hand, for isobaric pairs which involve several j-states or are in the 1 d 3 2 shell, ΔE c for a set of isotopes varies approximately as A- 1 3 .

Experimental study of (f722)7+ states in s-d shell nuclei☆

Abstract The (α, d) reactions on 24, 26Mg , 28,30 Si, 32,34 S, 36,38,40 Ar and 42 Ca at beam energies from 34 to 40 MeV were performed to search for ( f 7 2 2 )7 + levels in order to confirm and extend systematics observed by previous investigators. Supplementary ( 3 He, p) experiments on 24 Mg, 28 Si and 32 S were also performed. DWBA calculations proved quite useful in interpreting the experimental results. In addition, the 25 Mg(α,t) and 27 Al(α, 3 He) experiments were conducted to further distinguish the ( f 7 2 2 7 + states from ( d 5 2 f 7 2 )6 − levels in 26 Al and 28 Al. The latter states are expected to be populated with significant strength in (α, d) as are ( f 7 2 2 )7 + states. A nearly linear dependence of the (α, d) Q -values to the 7 + states versus atomic mass holds for all the s-d shell nuclei studied here. This Q -value linearity ends as the f 7 2 shell begins to fill although regularities are still apparent. A systematic and similar behavior of ( d 3 2 )3 + states was also observed.

Experimental study of ( f 7 2 2 )7 + states in s-d shell nuclei

Abstract The (α, d) reactions on 24, 26Mg , 28,30 Si, 32,34 S, 36,38,40 Ar and 42 Ca at beam energies from 34 to 40 MeV were performed to search for ( f 7 2 2 )7 + levels in order to confirm and extend systematics observed by previous investigators. Supplementary ( 3 He, p) experiments on 24 Mg, 28 Si and 32 S were also performed. DWBA calculations proved quite useful in interpreting the experimental results. In addition, the 25 Mg(α,t) and 27 Al(α, 3 He) experiments were conducted to further distinguish the ( f 7 2 2 7 + states from ( d 5 2 f 7 2 )6 − levels in 26 Al and 28 Al. The latter states are expected to be populated with significant strength in (α, d) as are ( f 7 2 2 )7 + states. A nearly linear dependence of the (α, d) Q -values to the 7 + states versus atomic mass holds for all the s-d shell nuclei studied here. This Q -value linearity ends as the f 7 2 shell begins to fill although regularities are still apparent. A systematic and similar behavior of ( d 3 2 )3 + states was also observed.

Structure of 17Ne ground state

Abstract Consideration of Coulomb energy for the lowest state with A=17, T= 3 2 , allows determination of the s2/d2 mixture in this state. The d2 configuration is found to dominate.

Systematics of energies of particle-hole states in the 2s-ld and 1f72 shells☆

Abstract The systematics of particle-hole states in the 2s-1d and 1f 7 2 shells have been analyzed in terms of the Bansal-French-Zamick weak coupling method. States considered are d − 3 2 f n 7 2 (J = 3 2 + ), ( s−d ) n 7 2 (J = 7 2 − ) and ( s−d ) n f 2 7 2 (J = 0 + and 7 + ) , the j n components corresponding to even-even ground states.

Experimental displacement energies of isobaric analog states in the 1f72 shell

Abstract Q-values for the (p, t), (p, 3He) and (p, d) reactions for twenty-five isobaric analog states in the 1 f 7 2 shell have been accurately measured. The corresponding experimental displacement energies are compared with recent model predictions.

Charge-dependent two-body interactions deduced from displacement energies in the shell

Abstract The f 7 2 shell model is used to relate displacement energies in the region A = 41–55 to a single-particle displacement energy and the differences between the proton-proton, proton-neutron, and neutron-neutron two-body matrix elements for J = 0, 2, 4 and 6. We find that the displacement energies for essentially all measured states (about 60) can be calculated to within an rms deviation of 12 keV by using a fixed set of these parameters. A few discrepancies such as for the 0 + and 2 + states in A = 42 can be due to large admixtures outside f 7 2 configurations. The deduced two-body matrix elements are compared with previous results for the d 5 2 s 1 2 and d 3 2 shells. The empirical results are compared with calculations of the Coulomb two-body matrix elements assuming j 2 configurations. The empirical pp-nn matrix elements are anomalous relative to these simple calculations. The size of the anomaly for the 2 J + 1 weighted average of the pp-nn interactions in the 1 f 7 2 shell is about the same as that deduced from the single-particle nuclei by Nolen and Schiffer; the J -dependence of the anomaly is very irregular. The empirical pn-nn matrix elements are consistent with zero except in the case of J = 0. The anomalies in both the pp-nn and pn-nn interactions may be due to configuration mixing and/or a charge dependence in the nucleon-nucleon interaction. The importance of the mass dependence in ħω for rms radii and Coulomb shifts is discussed. The displacement energies for proton rich f 7 2 nuclei are predicted and isospin-mixing matrix elements are calculated. Relations between the exact calculation and the generalized-seniority approximation are discussed.

Systematic effects of charge independence breaking on energies of analog states

Abstract Persistent and systematic evidence from energy differences of isobaric analog states demonstrates effects which are are attributed to the difference in the neutron-neutron and proton-neutron interaction in T = 1 states. These effects are of the order of magnitude expected from analysis of nucleon-nucleon scattering data.

Excitation of high-spin states in 49Ti by the (p, π-) and (d, α) reactions

States in 49Ti have been studied by the 51V(d, α)49Ti reaction with 28 MeV deuterons. Angular distributions are used to pick out those states that are populated by ΔL = 6 angular momentum transfer. Comparison with microscopic distorted wave calculations using f72 shell-model spectroscopic amplitudes suggest that the strong states observed at 3968 and 4388 KeV in the (d, α) reaction have spins 152− and 192− respectively, and are the same states that have been strongly in recent (p, π-) experiments.

Investigation of the (3He, 8He) reaction on 58Ni and 64Ni

Abstract The 64Ni(3He, 8He) reaction at 75.3 MeV was observed with a cross section at 10° of approximately 230 pb/sr using the Princeton Q3D spectrograph. For 58Ni and 50Ti targets, upper limits were set at 35 and 100 pb/sr at 10°.