A strong magnetic dipole excitation in 40Ca observed in high-resolution inelastic electron scattering and coherent spin-flip transitions due to ground-state correlations

Magnetic excitations in nuclei with neutron excess

“…Another indication of the need of extending the traditional RPA approach is coming from the experimental observation of non negligible B(M1) ↑ strength in 16 O and 40 Ca [43,47]. We have already mentioned that, in our approach, the B(M1)↑ strength is negligible for nuclei with all spin-orbit partner levels occupied.…”

“…We have already mentioned that, in our approach, the B(M1)↑ strength is negligible for nuclei with all spin-orbit partner levels occupied. Experimentally, a B(M1)↑ strength of about 1.0 µ 2 N has been identified in 16 O [43] and of about 1.2 µ 2 N in 40 Ca [47]. The description of these non-negligible strengths have been explained by considering 2p-2h excitations [48,49].…”

States in 40Ca near 12 MeV Excitation from the 39K(p, g)40Ca Reaction

“…An average of three recent measurements (Gross et al 1979;Moreh et al 1982;Burt et al 1982) gives a value of 1·15±0·05 /16 for this transition. This is close to the value predicted by recent theoretical calculations (Gross et al 1979;Burt et al 1982) which include up to 4-particle-4-hole components in the 40Ca ground state or 2hw excitations. These predictions range from 1·37 to 1·47 /16.…”

“…In the earlier measurement, Bartko and Thwaites (1968), using a natural KI target, reported only one level in this region, at 3·863 MeV (with Ex = 12·099 MeV, calculated by the authors using Q = 8·333 MeV). In the second measurement, with enriched 39KI and 39KBr targets, Heimlich and Mausberg (1970) reported levels at 3·850 Me V (Ex = 12·083 MeV) and 3·880MeV (Ex = 12·113 MeV). Only the lower of these two values could possibly overlap the energy of the state observed in (p, pi).…”

“…For example, in (p, p') studies at a bombarding energy of 201 MeV and at very forward angles which select only a few states, Crawley et al (1982) and Anantaraman et al (1981 and personal communication) noted a state at 12'063±0'015 MeV which has a AI = 0 angular distribution and a strength similar to the known 1 + state at 10· 32 MeV. However, in measurements of electron inelastic scattering at backward angles, carried out with good resolution, Steffen et al (1980) and Gross et al (1979) claimed no state with any measurable strength at an excitation energy near 12 MeV. At least three explanations are possible.…”