Giant monopole resonance strength in Si-28

Abstract

The giant resonance region in Si-28 was studied with inelastic scattering of 240 MeV alpha particles at small angles including 0 degrees. The giant resonance peak extended from E-x=12 MeV to 35 MeV and E0 strength corresponding to 54 +/- 6% of the isoscalar EO energy weighted sum rule was identified between E-x = 11-35 MeV with a centroid of 21.5 +/- 0.3 MeV and an rms width of 5.9 +/- 0.2 MeV. E2 strength corresponding to 32 +/- 5% of the isoscalar E2 sum rule was identified with a centroid of E-x = 19.0 +/- 0.2 MeV and rms width of 1.7 +/- 0.2 MeV. Elastic scattering was measured from theta(c.m.) = 3 degrees to 47 degrees and optical parameters obtained. Inelastic scattering to states at 1.78, 6.88, 10.2, and 11.1 MeV was measured and deformation lengths and L components extracted.