Observation of the High-Energy Octupole Giant Resonance with 800-MeV Protons

Abstract

Inelastic scattering of 800-MeV protons from 40 Ca, 116 Sn, and 208 Pb shows a broad giant resonance at an excitation energy of 110/'A 1 ' 3 MeV. The angular distributions are consistent only with scalar-isoscalar I =3 transfer. The excitation energy and width of this high-energy octupole giant resonance are in reasonable accord with theory. However, its energy-weighted sum-rule strength (~20%) is only about one half that predicted by randomphase-approximation calculations.

IsoscalarE0−E3strength inSn116,Youngblood1, Lui2, Clark3 et al. 2004Phys. Rev. C

“…Our results for the HEOR are compared with three other studies [35][36][37] in Table V. For 116 Sn the energies are in agreement, and except for the 800 MeV proton study [36] which reported only 22% of the EWSR, each study found approximately 75% of the EWSR expected in the HEOR [3].…”

“…For 116 Sn the energies are in agreement, and except for the 800 MeV proton study [36] which reported only 22% of the EWSR, each study found approximately 75% of the EWSR expected in the HEOR [3]. Bonin et al [38] also reported E3 strength centered ϳ23 MeV in 116 Sn with both 340 and 480 MeV ␣ scattering but identified less than 15% of the EWSR.…”

Isoscalar giant resonances inZr90,92,94

“…Using electron scattering, Nagao and Torizuka [9] in 1973 reported the observation of an isoscalar octupole state in 208 Pb at E x ∼ 19 MeV exhausting 44% of the * krishi@tunl.duke.edu & krishichayan@gmail.com E3 EWSR. Seven years later, Carey et al [10], using 800 MeV protons, reported identifying an octupole resonance in 40 Ca, 116 Sn, and 208 Pb at about E x = 110/A 1/3 MeV, while Morsch et al [11] using 152 MeV alpha particles reported both an octupole resonance at E x = 17.5 MeV and an isoscalar dipole resonance at E x = 21.3 MeV in 208 Pb. In 1976, Moss et al [12] using inelastic scattering of alpha particles, identified the 1 ω component of the isoscalar octupole giant resonance at E x ∼ 32/A 1/3 MeV in 7 medium mass nuclei.…”

Giant multipole resonances — perspectives after ten years

“…Suggestions of such strength were also made through the 197 Au(p,p') reaction 55 ) and the 116 Sn(e,e') reaction. 26 ) The fraction of the EWSR depleted in the so-called low-energy octupole resonance is 10-205= for most of the nuclei studied. No LEOR is observed in '*°Ca or 208 Pb.…”

“…Within the past few months suggestions have been made for the systematic observation of a 3tfu giant octupole resonance (GOR) through inelastic scattering of 800-MeV protons, 26 ) 172-MeV alpha-particles 27 ), and 110-140 MeV helium-3 particles. Figure 19 shows inelastic proton spectra 26 ) (800 MeV incident protons) on 208 Pb, 116 Sn and U0 Ca. In each case a peak is observed (labeled HEOR, high-energy octupole resonance) at'an excitation energy above the GQR peak.…”