Norton M. Hintz

The (p, t) reactions on nuclei in the rare earth region

Abstract The (p, t) reactions on isotopic targets of 178, 180 Hf and all the stable isotopes of Yb and on natural targets of Gd, Dy, Er, Hf, Ta, W, Os and Au were studied at a beam energy of 19 MeV with an average resolution of 12 keV. A split-pole magnetic spectrometer was used to measure (p, t) Q -values and absolute differential cross sections. On the basis of angular distribution shapes definite 0 + and tentative 2 + assignments were made. Rotational bands were identified assuming an I ( I +1) spacing. The (p, t) reaction populates excited 0 + states strongly in 174 Yb, 176 Hf, 166 Yb and several Gd, Dy and Er isotopes. The 174 Yb and 176 Hf 0 + states are discussed in terms of the pairing phase transition and in terms of Nilsson orbitals with unequal (p, t) reaction amplitudes. Members of gamma and octupole vibrational bands were observed in the even- N nuclei. The lowest L = 0 transfers to states in 169, 171 Yb were found to have less than 55% of the strength to ground states in adjacent even- N nuclei. A strong L = 0 transfer to a state at 1513 keV in 171 Yb indicates the presence of a possible K = 0 core vibration coupled to the unpaired 5 2 [512] neutron. The natural targets have furnished information on trends in cross sections for members of ground bands, gamma bandheads, 3 − octupole states, and strongly excited 0 + states.

The (p, t) reaction on even isotopes of Sm

Abstract The reactions 148,150,152,154Sm(p, t) were studied at a bombarding energy of 19.00 MeV. Absolute differential (p, t) cross sections were measured with a split-pole magnetic spectrometer. Trends in the triton angular distribution shapes were identified for angularmomentum transfer L of 0, 2 and 3 units. On the basis of the angular-distribution shapes, definite 0+ and 3− assignments and tentative 2+ assignments were made. The (p, t) reaction is observed to populate excited 0+ states in Sm with unusually high intensity, as does the (t, p) reaction. A qualitative explanation is given based on the model of Kumar and Baranger, in which the distinction between spherical and deformed nuclei is softened. In particular, 0+ states at 1.255 MeV in 150Sm and 1.426 MeV in 148Sm that are strongly excited by the (p,t) reaction may be interpreted as “deformed” states in nuclei with “spherical” ground states. Rotational bands built on these 0+ states are identified in the (p, t) spectra. These bands are seen to fit into the systematics of the Sm ground-state bands.

Elastic differential cross sections and analyzing powers for p+40,42,44,48Ca at 0.8 GeV☆

Abstract Differential cross sections and analyzing powers for the elastic scattering of 800 MeV polarized protons from 40,42,44,48Ca are reported. A first-order, spin-dependent KMT optical potential analysis is presented from which the rms radii of the neutron densities are deduced. A comparison of these results with other determinations and with various theoretical predictions is given.

Elastic scattering of 0.8-GeV protons from C12, Ni58, and Pb208

Differential cross sections for elastic scattering of 0.8-GeV protons from /sup 12/C, /sup 58/Ni, and /sup 208/Pb have been measured. Preliminary analysis of the data in terms of the Kerman-McManus-Thaler formalism with spin-dependent nucleon-nucleon amplitudes shows sensitivity to details of proton and neutron matter distributions.

0.8 GeV p + Pb 208 elastic scattering and the quantity Δ r np

Analyses of 0.8 and 1 GeV p+/sup 208/Pb elastic angular distribution data have obtained neutron-proton root-mean-square radius differences (..delta..r/sub n/p) which are not consistent. Therefore, the 0.8 GeV experiment was repeated using a high resolution spectrometer. The new higher precision data are consistent with the older data, apart from a 15% overall normalization difference. A second order Kerman-McManus-Thaler optical model analysis of the new data, using a model-independent neutron density, yields ..delta..r/sub n/p=0.14 +- 0.04 fm, in good agreement with the most recent result obtained (0.16 +- 0.05 fm) from a similar analysis of the older 0.8 GeV data. In addition, the elastic angular distribution was extended to 42.5/sup 0/ center of mass in order to explore the momentum transfer region from 3.5 to 5.3 fm/sup -1/. Although the familiar diffraction pattern persists to 42.5/sup 0/, it was not possible within the framework of our application of the Kerman-McManus-Thaler optical model to fit the data even qualitatively at the larger momentum transfers.

Elastic differential cross sections and analyzing powers for p + 54Fe, 58,64Ni at 800 MeV

Abstract Elastic scattering analyzing powers and differential cross sections for 800 MeV → p + 54Fe, 58,64Ni are reported. An approximately mode-independent technique is used to extract information concerning the neutron density distributions of these nuclei.

Analysis of elastic scattering of 0.8 GeV polarized protons from 116Sn and 124Sn

Abstract Differential cross section and analyzing power data for elastic scattering of 0.8 GeV polarized protons from 116Sn and 124Sn are analyzed in terms of a spin-dependent Kerman-McManus-Thaler formalism. Neutron matter densities and rms radii are deduced with careful attention to sources of error, and found to be in good agreement with Hartree-Fock predictions.

A study of 50V using the direct reactions 49Ti (3He, d) and 51V(d, t)

Abstract Energy levels in 50 V up to 4.3 MeV have been studied using the 49 Ti( 3 He, d) 50 V and 51 V(d,t) 50 V reactions with 3 He particles of 22 MeV and deuterons of 19.5 MeV incident energy. More than eighty levels are seen, with angular distributions taken for forty-one levels in the ( 3 He, d) reaction and for the ten lowest levels in the (d, t) reaction. The angular distributions are compared with the distorted-wave Born approximation (DWBA) to extract the l -values of the transferred nucleons and obtain the spectroscopic strengths. In the stripping reaction, a small amount of l = 0 and l = 2 strength is seen, indicating the presence of s and d proton holes in the g.s. of 49 Ti. The results are compared with a recent shell-model calculation based on an ( f 7 2 ) n configuration, and show qualitative agreement.

Radiative capture above the giant resonance in C13

Abstract Excitation functions for the radiative capture reaction, B 11 (p, γ)C 12 , to the ground and first excited states of C 12 have been measured in the region above the giant resonance ( E p = 15 to 25 MeV. A component of the dipole state, predicted at an excitation energy of 34.3 MeV in C 12 by the particle-hole calculations of Vinh-Mau and Brown, has been found at an energy of 34.4±0.5 MeV. However, the ratio of proton capture at the 34.4 MeV state to that at the main dipole component at 22 MeV is an order of magnitude less than that implied by the Vinh-Mau and Brown model. Some data have been obtained for the reaction Li 7 (p, γ)Be 8 . Both experiments suggest giant dipole resonances built on the first excited states of Be 8 and C 12 .

Coupled-channels effects in 0.8 GeV proton inelastic scattering from 58Ni

Abstract New differential cross sections for 0.8 GeV proton inelastic excitation of the first 2+ and 4+ states in 58Ni are compared with distorted wave Born approximation and coupled-channels predictions. Multistep processes and multi-phonon mixing are both shown to be important in describing the excitation of the 4+ state.