E. E. Gross

Elastic and inelastic scattering of 88 MeV 6Li ions

Abstract The elastic scattering of 88 MeV 6 Li ions has been studied for eleven targets ranging in mass from 24 Mg to 208 Pb. Angular distributions were measured from about 10° c.m. in steps of 0.5°, mostly out to 60 or 70° c.m. where the elastic cross sections range from 10 −3 to 10 −5 of the Rutherford values. Inelastic data for exciting the lowest 2 + states of 24,26 Mg and 60 Ni were also obtained. The elastic data were analyzed using the optical model, with potentials of both Woods-Saxon and double-folding forms. The analysis confirms that the potentials for 6 Li obtained from the folding model with the M3Y interaction need renormalizing by about 0.6, in agreement with results obtained at other energies. The inelastic data were compared to distorted-wave calculations. Coupled-channels analyses were also made for 24, 26 Mg, 60 Ni and 59 Co. Reorientation effects were found to be important to give the correct 2 + angular distributions for 24, 26 Mg and could also account for the differences between the elastic scattering from the odd- A and adjacent even- A targets.

Elastic and inelastic scattering of 158 MeV 9Be ions

Abstract The elastic scattering of 158 MeV 9 Be ions was measured for seven targets ranging in mass from 12 to 197. Inelastic data for exciting the lowest 2 + states of 12 C, 26 Mg and 60 Ni were also obtained. The elastic data for 12 C and 16 O show pronounced structures at the most forward angles which are rapidly damped as the scattering angle increases. The distributions for 26 Mg and 27 Al show marked structure with significant odd-even differences that can be ascribed to quadrupole scattering from the 27 Al ground state. The elastic data were analyzed using the optical model with both Woods-Saxon and folding-model potentials. The folded potentials are too strong and require renormalization; they do not give good fits to the data for the lighter targets. The inelastic data were compared to distorted-wave calculations.

The deuteron D-state and the π++d →p+p reaction

Abstract Angular distributions for the reaction π + + d → p + p at 40, 50, and 60 MeV are compared with calculations employing a π N t matrix both on and off-shell and two different models for the deuteron. Within this framework, the data require a 4% D-state admisture.

Validity of collective model DWBA analysis for intermediate energy proton scattering to low-lying states of 208Pb

Abstract New measurements of inelastic proton scattering to low-lying collective states of 208 Pb at 200 and 400 MeV are reported. Deformation lengths ( δ H = βR ) extracted from angular distributions for the 3 − (2.614), 5 − 1 (3.198 MeV), 5 − 2 (3.709 MeV), 2 + (4.086 MeV) and 4 + (4.324 MeV) states are in good accord with values extracted at other incident proton energies. The fact that the deformation lengths for these levels are independent of incident proton energy within experimental uncertainty provides further support of the validity of the collective DWBA for medium energy proton scattering to strongly excited states. Advantage is taken of this to extract more precise values for the ratio of neutron to proton multipole matrix elements for both the low-lying states and the giant quadrupole resonance at 10.6 MeV.

Mutual excitation of 22Ne and 126Te in inelastic scattering

Abstract Angular distribution data for the mutual excitation of the 126 Te and 22 Ne 2 + states have been measured for the inelastic scattering of 93.5 MeV 22 Ne on 126 Te. Data for transitions to the ground states, the 126 Te 2 + state and the 22 Ne 2 + state were also obtained. A coupled-channels analysis of the reaction is found to provide a good description of the general features of the data.

Analyzing power for the inelastic continuum with 200 MeV protons

Abstract Inelastic proton scattering from targets of 60 Ni, 90 Zr, and 208 Pb has been studied using 200-MeV polarized and unpolarized protons. The behavior with angle of a narrow region at the peak of the continuum underneath the giant resonance spectra follows that expected for free nucleon-nucleon scattering, modified by an energy shift dependent on target mass. Analyzing power results support the hypothesis that single-step quasifree scattering represents a significant fraction of the overall inelastic scattering for the excitation region near the proposed quasifree peak, but indicate that other processes start to dominate above this excitation region.

Elastic and inelastic scattering of 79.5 MeV 11B and 87.5 MeV 10B ions

Abstract The elastic scattering of 79.5 MeV 11 B ions has been studied for seven targets ranging in mass from 24 Mg to 197 Au and of 87.5 MeV 10 B ions for three of these targets ( 24, 25 Mg, 60 Ni). Angular distributions were measured from ~10° c.m. in steps of 0.5°, to angles beyond 40° c.m. where the elastic cross sections are ≲ 10 −3 of the Rutherford values (except for 197 Au). Inelastic data for exciting the lowest 2 + states of 24,26 Mg and 60 Ni were also obtained. Important odd- A -even- A differences are observed in the 11 B elastic angular distributions for the Mg and Al targets; for 10 B scattering these are obscured by projectile quadrupole moment effects on the elastic scattering. The elastic data were analyzed using the optical model with potentials of both Woods-Saxon and double-folding form. The data for both 10 B and 11 B are consistent with the potential obtained in the folding model with the M3Y interaction without renormalization. The inelastic data were analyzed by the distorted-waves method.

The vertical drift chamber as a high resolution focal plane detector for heavy ions

Abstract A vertical drift chamber in the focal plane of a magnetic spectrometer has been tested with 12 C(129 MeV), 14 N(176 MeV) and 16 O (140 MeV) ions. An experimental position resolution of ≤ 0.5 mm was measured,corresponding to an intrinsic detector resolution of about 0.1 mm (fwhm). The angle of the ion trajectory with respect to the focal plane was measured to within ∼ 10 mrad, which corresponds to an intrinsic detector resolution of about 7 mrad. The angle measuring capability of the counter permits the measurement of angular distributions across the spectrometer opening and the correction of the counter data for magnet aberrations. Details of the electronics and gas handling systems and the detector performance with heavy ions are presented.

Elastic and inelastic scattering of 120 MeV 18O from 208Pb and the spin alignment of the 2+ state of 18O

Abstract The elastic and inelastic scattering of 18 O ions at 120 MeV from a target of 208 Pb have been studied. Cross sections for excitation of the 2 + state at 1.982 MeV in 18 O and of the 3 − state at 2.61 MeV in 208 Pb were measured. In addition, the populations of the m -substates for the 18 O excitation were deduced from the Doppler-broadened line shapes. The data were subjected to a coupled-channels analysis using either Woods-Saxon or folding-model potentials. In addition, the 18 O excitation was found to be described very well by use of a semi-microscopic model. The analyses consistently indicated the presence of a positive static hexadecapole moment of several e · fm 4 for the 2 + state of 18 O. The m -substate population distributions were found to be better fitted if a vector spin-orbit coupling was introduced for the 2 + state of 18 O with a sign opposite to that for the nucleon-nucleus case.

On the validity of microscopic calculations for inelastic proton scattering

Abstract Recent measurements of transition rates for low-lying collective states and giant resonances in 208 Pb using inelastic scattering of 200 and 334 MeV protons are in accord with accepted values. This is in sharp disagreement with earlier medium-energy proton inelastic scattering studies in which the validity of the collective model formalism was questioned. Combining these results with measurements at other energies, we conclude that the extraction of deformation lengths with the collective distorted wave Born approximation formalism is satisfactory to at least 800 MeV. The present results bring into question the microscopic calculations of inelastic scattering using RPA wave functions.