Low-lying quadrupole and octupole collective excitations in the 112,116,118,120,122,124Sn isotopes
Abstract
Background: In recent years, considerable interest has been focused on the study of the effect of neutron skin on the collective properties of vibrational nuclei. This can be best evidenced by exclusively determining neutron and proton transition matrix elements involved in a particular excitation by investigating the Coulomb-nuclear interference feature of inelastic scattering.
Purpose: Measurement of angular distributions of the inelastic scattering cross sections for excitations to low-lying 21+ and 31- states in 112,116,118,120,122,124Sn using 7Li beam as probe at Elab=28 MeV and determination of neutron and proton transition matrix elements involved in each excitation. Methods: Projectilelike fragments were detected using six sets of Si-surface barrier detector telescopes to measure the cross sections for elastic and inelastic scattering channels. Optical model analysis of elastic scattering data, coupled reaction channels, and continuum discretized coupled channels calculations were performed to understand the measured differential cross sections. An attempt has been made to extract the microscopic mass and charge deformation lengths. Results: For the 21+ state, experimental B (E 2 ) values are in good agreement with existing results obtained by electromagnetic methods. Charge and mass quadrupole vibrations are homogeneous. Significant differences are observed for excitation to the 31- state across the Sn isotopic chain. Available structural information for collective octupole vibrations could not reproduce the present data for this excitation. Results show much lower values of octupole mass deformation parameters. Conclusions: Isoscalar nature of surface vibrations for the 21+ state in Sn isotopes is verified, with Mn/Mp∼N /Z . For the 31- state, damped mass vibration is the primary observation. On comparison with existing estimates, a significant deviation from isoscalar nature is conjectured for this excitation, when probed with 7Li.- Publication:
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Physical Review C
- Pub Date:
- March 2019
- DOI:
- 10.1103/PhysRevC.99.034609
- Bibcode:
- 2019PhRvC..99c4609K