Particle-hole strength excited in theCa40(p,n)40

Abstract

The~Ca{p,n) Sc reaction was studied at 134 MeV. Neutron energy spectra were measured by the time-of-Aight technique with resolutions of 220 keV at angles from 0' to 41' and 415 keV out to 62'. The 2,3,4,5 band of states based on the (f7qs, dqq2) lplh structure was observed at low excitation energies, in good agreement with known analog states in~C a and K. The shapes of the cross-section and analyzing-power angular distributions are in good agreement with distorted-w'ave impulse-approximation calculations using simple 1p1h (Tamm-Dancoff approximation) shell-model wave functions. A relatively strong transition to a state at E"=2. 3 MeV with L =3 is identified tentatively as a 4 state with the predominant 1p1h structure (1f7qt, 2s~qi). The excitation of the ( T = 1) 6 (f7',dqq2) stretched state is observed near E, =7 MeV, fragmented over approximately 3MeV. The normalization factor required to make a distorted-wave impulse-approximation calculation agree in magnitude with the 6 excitation is 0.35, which is larger than the normalization factor for this excitation in mass 28, analyzed in a similar manner. The I. =1 giant resonance is observed to be centered near E"=10MeV with a width (full width at half maximum) of about 5 MeV, and a distorted-eave impulse-approximation normalization factor of 0.16. Two 1 excitations are observed at E"=2.7 and 4.3 MeV which indicate directly the presence of ground-state correlations in the Ca target. The fact that the analog of the higher 1+ excitation is not seen in inelastic electron scattering indicates strong interference between spin and orbital current contributions. The effect of ground-state correlations on the 1plh wave functions was investigated by performing calculations which allowed multiparticle-multihole correlations in the d3qt and f7/2 orbitals. The distorted-wave impulse-approximation normalization factors obtained with these wave functions were found to increase by a factor of about 2 relative to those obtained with~C a assumed to be a closed core.

γ rays from muon capture in natural Ca, Fe, and Ni

“…The comparisons in Table IX are quite satisfactory, though the measurements disagree slightly but are not wildly outside the errors. We also include the yield from the reaction 40 Ca(p, n) 40 Sc observed by Chittrakarn et al [4]. There are two obvious difficulties with this comparison.…”

“…Yields for muon capture to specific levels in 40 K with the cascading effects removed, compared to the earlier results of Igo-Kemenes et al [3], all given as yield per capture. Also a comparison is made to the reaction 40 Ca(p, n) 40 Sc from Chittrakarn et al [4] at about 10 • in the lab.…”

“…These machines had poor duty cycles, so it is not surprising that we can improve on their results. We can compare the Ca results for the (µ − , ν) reaction with the (p, n) reaction studied by Chittrakarn et al [4]; this reaction will be very similar to the (d, 2 He) reaction, which is known to be similar to muon capture. For the (µ − , νn) reaction we compare with a photonuclear experiment by Ullrich and Krauth [5], which was also available to Igo-Kemenes et al [3].…”

Magnetic dipole probes of the sd and pf shell crossing in the 36,38Ar isotopes

“…Thus, shell closures are not 'rigid' and there have been for a long time indications for cross-shell correlations even in nuclei close to classical double-magic nuclei like 40 Ca. For this nucleus, these include the observation of a strong M1 transition [2] and of a non-vanishing Gamow-Teller (GT) strength built on the 40 Ca ground state [4,5,6]. On the theory side, recent studies [7,8] show that there are very large admixtures of sd configurations in low-energy states of Ca isotopes with A ≥ 40, although these nuclei are usually considered as "good" pf shell nuclei.…”

Excitation of6−and7+stretched states in theAnderson1, Baldwin2, Garcia3 et al. 1992Phys. Rev. CSelf Cite

“…22; however, an analysis [3] of a Ca(d, p) 'Ca(J"= -, '+) experiment yielded a value of 0.78 for G. Noting that in his model G = 1.0 implies that the Ca ground state is entirely core excited, Zamick states that G =0.78 would require the unperturbed energy of the two-particletwo-hole (2p-2h) state to be lower than the simple shell-model state, which "would be a major catastrophe for the shell model. "…”