The 42, 44Ca(p, d) 41, 43Ca reactions at 26.5 MeV

Abstract

The 42Ca(p, d) 41Ca and 44Ca(p, d) 43Ca reactions at 26.5 MeV have been examined with 100 keV resolution to obtain nuclear structure information on the levels observed in 41Ca and 43Ca up to an excitation energy of approximately 8 MeV and on the ground state wave functions of 42Ca and 44Ca. The strong 2 s 1 2 and 1 d 3 2 hole states were verified at 2.68 MeV and 2.02 MeV, respectively, in 41Ca and at 1.96 MeV and 0.99 MeV, respectively, in 43Ca. Isobaric analog states ( T = T z +1) were located at 5.84±0.05 MeV (J π = 3 2 +), 6.82±0.05 MeV ( 1 2 +) and 7.13±0.05 MeV ( 7 2 −) in 41 Ca and 7.97±0.05 MeV ( 3 2 +) in 43 Ca . The presence of additional levels in both nuclei with l n = 0 and l n = 2 transitions implies that the one-hole state strength is distributed over several levels. Evidence for the splitting of the 1 f 7 2 single-particle strength has been found with the excitation of states with l n = 3 transitions at 2.98 MeV and 3.28 MeV in 41Ca and 43Ca, respectively, whose spectroscopic strengths are approximately 11% and 7.5%, respectively, of the corresponding ground state transitions. Excitation of the 7.13 MeV 7 2 −, T = 3 2 ) level in 41Ca indicates the presence of four-particle-two-hole components in the 42Ca ground state. Using sum rules, we find the average number of 1 f 7 2 protons in the 42Ca ground state to be approximately 0.6. The different relative spectroscopic strengths for the (p, d) and (d, p) reactions leading to 3 2 − states in 43Ca at 0.59 MeV and 2.05 MeV demonstrates that both [(1 f 7 2 2(2 p 3 2 ) 2] and [(1 f 7 2 3(2 p 3 2 )] admixtures are present in the 44Ca ground state. Indication of an [(1 f 7 2 3(1 f 5 2 )] admixtures found from the excitation of the 5 2 − state at 0.373 MeV in 43Ca. A non-pick-up angular distribution to the 1.68 MeV level in 43Ca was observed. If the previously made tentative assignment of 11 2 − for this state is correct, this transition proceeds by higher-order reaction mechanisms. The spectroscopic strengths for the levels excited were derived from DWBA calculations using form factors modified by finite-range and non-local corrections in the local-energy approximation. The resulting shapes of the angular distributions were in better agreement with the experimental results than those for zero-range local calculations; the derived spectroscopic strengths were also less sensitive to the choice of optical potential parameters and in better agreement with sum-rule predictions. Comparisons between the experimental spectroscopic strengths and those predicted by theoretical wave functions are made where such wave functions are known.