Experimental and Theoretical Studies of the Giant Resonances in Nuclei.
In the first part of this thesis, a classical model is constructed in which elastically coupled, elastic proton and neutron fluids can oscillate in transverse and longitudinal isoscalar and isovector modes. By fixing the Lame coefficients for nuclear matter empirically, the isoscalar and isovector giant resonance energies are calculated for the E0, E1, E2, E3, M1 and M2 multipoles, and compared with the available experimental data on these collective states. With these same coefficients, the Poisson ratio of nuclear matter is determined to be 0.485. The second part presents an experimental search for the polarization of photoneutrons from the reaction ('16)O((gamma),(')n(,0))('15)O at 90(DEGREES) in the photon energy range between 17 and 22 MeV using the nanosecond neutron time-of-flight spectrometer associated with the Yale University Electron Linear Accelerator. The polarization was measured with an absolutely calibrated ('12)C analyzer. For the first time, fine structure has been observed in the polarization of photoneutrons at energies below the giant E1 states; this is clear evidence of M1 (or E2) photon absorption in ('16)O. The results are compared with those from recent ('15)N((')p,(gamma)(,0))('16)O experiments, and constitute evidence of significant ground-state correlations in this doubly closed-shell nucleus.
- Pub Date:
- September 1984
- Physics: Nuclear