SPECTROSCOPIC FACTORS FROM ONE-PROTON STRIPPING REACTIONS ON SD-SHELLNUCLEI - EXPERIMENTAL MEASUREMENTS AND SHELL-MODEL CALCULATIONS

The (He-3,d) reaction has been investigated at 25 MeV on the target nu clei O-16, O-18, F-19, Na-23, Mg-24, Mg-25, Mg-26, Al-27, Si-28, Si-29 , Si-30, P-31, S-32, S-34, Cl-35, Cl-37 and K-39. Attention is restric ted to the few even-parity levels in each final nucleus which are stro ngly populated. Values of the single-nucleon spectroscopic factors C2S are obtained from the differential cross sections measured for these levels by analyzing them in the framework of the DWBA theory of nuclea r reactions. The DWBA calculations use sets of He-3 and deuteron optic al-potential parameters which are experimentally validated and interna lly consistent. The absolute values of C2S thus extracted are rather i nsensitive to which sets of equivalent optical-model parameters are us ed in the DWBA analyses (variations of the order of +/-15%) and the va riations in the relative values for the different transitions are very insensitive to these choices. Most of the sensitivity which does exis t can be traced to the specification of the absorptive part of the deu teron potential. The values of C2S are not sensitive to the presence o f spin-orbit terms in either the deuteron or the He-3 potential. Contr ary to the case for optical-model potentials, however, absolute values of C2S are very sensitive to the radius parameter r0 chosen for the p otential which binds the transferred proton, although relative values are almost completely insensitive to this choice. The effects of the s pin-orbit part of this bound-state potential on j = l + 1/2 and j = l - 1/2 transitions have also been carefully investigated. Evidence is d eveloped that the radius parameter rs.0 of the spin-orbit part of the bound-state potential should be smaller than that of the central part. The values of C2S extracted from the present data both with standard DWBA analyses (r0 = r(s.o.) and a0 = a(s.o)) and with analyses which i ncorporate a modified treatment of the spin-orbit term of the bound-st ate potential (r0 not-equal r(s.o.) and a0 not-equal a(s.o.)) are comp ared with the predictions of the USD shell-model hamiltonian. The rati os between the experimentally based spectroscopic factors and the mode l predictions exhibit a marked difference between transitions into the 1d3/2 orbit and transitions into the 1d5/2 orbit when the standard DW BA analysis is used. However, this difference between 1d3/2 and 1d5/2 transitions is greatly reduced if, while the conventional values r0 = 1.25 fm and a0 = 0.65 fm continue to be used for the central component of the bound-state potential, values of r(s.o) = 1.00 fm and a(s.o) = 0.52 fm are used for the-spin-orbit part.