Abstract
Beams of 96 and 115 MeV particles have been used to study the distribution of isoscalar octupole strength in 18 nuclei from to . A prominent broad peak ( MeV) is observed at MeV in nuclei from to . No broad peak is observed in this excitation energy range in or and lighter nuclei. The oscillatory angular distributions of the () reaction exciting this peak are in excellent agreement with distorted-wave Born approximation calculations. Studies of the angular range from in indicate very little contribution from strength. Energy- weighted sum rule fractions for this low-energy octupole resonance are generally in the range from 15% to 20%; this corresponds to ½ to of the expected octupole strength. The overall distribution of octupole strength in spherical nuclei, including the absence of the low-energy octupole resonance in and , is in very good agreement with random-phase approximation calculations. The low-energy octupole resonance undergoes a pronounced change in structure in soft-vibrational and deformed nuclei. Theoretical calculations for the low-energy octupole resonance in account qualitatively for the data.
NUCLEAR REACTIONS , , , , , , , Ag (nat), , , , , , , , , , MeV measured , giant resonances, deduced , .
- Received 21 February 1978
DOI:https://doi.org/10.1103/PhysRevC.18.741
©1978 American Physical Society