Coupling of particles and holes with proton pairing vibrations nearZ=50

Abstract

Measurements of the ('He, n) reaction have been carried out on a number of odd-Z targets in the vicinity of the closed proton shell at Z=50. For the targets ' ' Ag and "" In, the results can be interpreted in terms of the coupling of proton particles or holes to the known pairing vibrational states in neighboring tin nuclei. For targets of ' " Sb, the expected I.=0 transition strength is observed, but is found to be spread over several final states.

On the (3He,n) reaction in theA ? 100 region

“…The fact that only pure configurations were considered allows the factorization of the calculated cross sections into a nuclear reaction part and a nuclear structure part, the latter being contained in the enhancement factor e. The shape of the calculated angular distributions for L= 0 transitions, and in particular its strong forward peak, is insensitive, at least within reasonable limits, to the following choices: (i) the optical model parameters; (ii) the Woods-Saxon potential for the transferred protons; (iii) the configurations of the transferred pair. Furthermore, it agrees with the shape of the experimental angular distributions, as already shown in [6][7][8] and further confirmed in the present work. However, the absolute values of the calculated angular distributions, and hence the enhancement factors e, are very sensitive to these choices, and in particular to the adopted configurations.…”

“…We shall now examine the uncertainties in the ratios between these enhancement factors e for different nuclei, which are induced by the various possible choices (i) to (iii) just mentioned. As preliminary remarks, the relative values of the experimental cross sections for different nuclei, measured under the same experimental conditions as pointed out before, have minimal uncertainties due to the uncertainties in the thicknesses of the targets used; these amount to 15% for Zr and Mo, 30% for SSSr and I~ and 10% for Pd, Ag and Cd targets [6][7][8]. The statistical uncertainties on the 0 ~ cross sections, on the other hand, are negligible by comparison with the other sources of uncertainties.…”

“…In the DWBA calculations, the optical model parameters for the 3He's and neutrons, and the WoodsSaxon potential used to compute the single-particle wave functions for the transferred protons and the form factor of the transferred pair, were those adopted in [8]; they are given in Table 1, and they were kept the same for all nuclei investigated. The configurations for the transferred proton pair were (lg9/2) a, (2pl/2) a, (2p3/2) z or (lf5/2) 2, i.e.…”

“…The experimental 0 ~ differential cross sections for the A(3He, n)B reactions [6][7][8] have been compared to the results of DWBA calculations, carried out using the programme DWUCK4 [9], in order to obtain the so-called enhancement factors e, defined in [6][7][8], and given by:…”

“…Simple analytical expressions can be obtained in the two models for the relative intensities of the L=0 transfers between the 0 § ground states of even-even nuclei [4,5]. Extensive experimental data are available on the (3He, n) two-proton transfer reaction in the A~100 region [6][7][8], and in particular on the cross sections at 0 ~ for the L=0 transfers between the ground states of the even-even Sr, Zr, Mo, Ru, Pd, Cd and Sn isotopes I- 6,7], and between the lowest 1/2-levels in the odd-Z Ag and In isotopes [8]. They were obtained at the same laboratory, using the same 3He energy (25.4MeV), and under the same experimental conditions.…”