F.E. Bertrand

Evidence from inelastic proton scattering for a giant quadrupole vibration in spherical nuclei

Abstract A systematic study of inelastic proton continuum spectra produced at small angles by bombardment of 27Al, 54Fe, 120Sn and 209Bi with 62 MeV protons suggests the existence of a collective region in the continuum with properties of a giant quadrupole vibration.

Coulomb excitation of giant resonances in 208Pb by E = 84 MeV/Nucleon 17O projectiles

Abstract Inelastic scattering of 84 MeV/nucleon 17 O on 208 Pb has been measured between 1.5° ⩽ θ CM ⩽5.0°. The giant resonance structure near 12 MeV is excited with a differential cross section of more than 2b/sr and exhibits a peak-to-continuum ratio as large as 6 to 1. The major part of the cross section can be ascribed to Coulomb excitation of the isovector giant dipole and the giant quadrupole resonance. From the Coulomb excitation of the GQR we deduce a B (E2) fx = 0.53 ±0.11 e 2 b 2 which is that expected for a nearly pure isoscalar resonance which exhausts ≈ 60% of the EWSR.

Systematics of the isoscalar giant monopole resonance from 60 MeV inelastic proton scattering

Abstract Evidence for an isoscalar giant monopole resonance is provided for seven nuclei with A ⩾ 58. The resonance excitation energy is ≈ 80 × A −1 3 MeV . For nuclei with A ⩾ 0, nearly 100% of the L = 0, T = 0 energy-weighted sum rule is depleted in the resonance, in agreement with earlier work on 208Pb and 144Sm. Only ≈30% is found in 58Ni, and no clear evidence is found for localized monopole strength in 40Ca.

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.

Giant Quadrupole Resonance in 24,26Mg : A Comparison of Inelastic-Scattering and α-Capture Experiments

The distribution of giant quadrupole resonance strength in /sup 24,26/Mg obtained from inelastic ..cap alpha..- and proton-scattering experiments and ..cap alpha..-capture experiments have now been shown to be compatible. The results show that the giant quadrupole resonance strength in /sup 24/Mg and /sup 26/Mg is fragmented into several states or clusters of states and suggest that the giant quadrupole resonance states have very different ..cap alpha../sub 0/-decay strength.

Giant quadrupole resonance in /sup 24,26/Mg: A comparison of inelastic-scattering and. cap alpha. -capture experiments

The distribution of giant quadrupole resonance strength in /sup 24,26/Mg obtained from inelastic ..cap alpha..- and proton-scattering experiments and ..cap alpha..-capture experiments have now been shown to be compatible. The results show that the giant quadrupole resonance strength in /sup 24/Mg and /sup 26/Mg is fragmented into several states or clusters of states and suggest that the giant quadrupole resonance states have very different ..cap alpha../sub 0/-decay strength.

Large deformation in A ~ 170 nuclei at high excitation energies

Abstract The γ -ray decay of the giant dipole resonance was measured in coincidence with fission fragments following the fusion reaction 16 O+ 159 Tb forming 175 Ta at 123.4 MeV excitation energy. A large splitting of the giant dipole resonance (GDR) energies in the compound system was observed corresponding to a large deformation of β =0.55.

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.

ON THE EXCITATION OF ISOVECTOR DIPOLE STRENGTH BY INELASTIC PROTON-SCATTERING IN THE GIANT-RESONANCE REGION IN LIGHT-NUCLEI

Abstract A detailed comparison between inelastic α and p scattering in the giant resonance region of 24, 26 Mg, 28 Si and 40 Ca shows that there is no evidence for ΔT = 1, E1 excitation in the (p, p′) spectra. This is consistent with DWBA calculations using a recently obtained isovector interaction potential.