Giant resonance study by proton and alpha inelastic scattering at and near zero degrees at RCNP

Abstract

The (Delta)L = 0 collective excitations have been investigated by measuring cross sections, polarization transfer observable (D(sub SS)(= D(sub NN)) and D(sub LL)), and proton decays from the excited states in inelastic scattering of 394 MeV protons from Ni-58 at zero degrees. The spin-flip and non-spin-flip cross sections have been decomposed using the quantity of total spin transfer defined as Sigma = (3-(2D(sub SS) + D(sub LL)))/4. From the non-spin-flip cross section, the strength of the Giant Monopole Resonance (GMR) has been deduced by subtracting contributions of the Isovector Giant Dipole Resonance (IVGDR) using the E1 strength obtained by electron scattering and DWBA (Distorted Wave Born Approximation) calculations with macroscopic form factors. In the preliminary results, about 70 percent of E0 sum rule limit has been exhausted. Angular distributions in extremely forward angles are also important for the study of such giant resonances. In the recent R & D experiment, remarkably clean spectra have been obtained at scattering angles from 2 deg to 5 deg for 400 MeV alpha scattering.

ΔL=0集団励起を研究するために、断面、偏極遷移オブザーバブル(D(sub SS)(=D(sub NN))およびD(sub LL))、および0度におけるNi-58からの394MeV陽子の非弾性放散における励起状態からの陽子崩壊を測定した。全スピン遷移量をΣ=(3-(2D(sub SS)+D(sub LL)))/4と定義して、スピンフリップおよび非スピンフリップ断面を分解した。電子散乱から、および巨視的形状因子をもつDWBA(歪曲波ボルン近似)計算から得られたE1強度を使用して、等ベクトル巨大双極子共鳴(IVGDR)の影響を非スピンフリップ断面から差し引くことにより、巨大単極子共鳴(GMR)の強度を導出した。予備検討の結果では、E0和則極限の約70%を消耗した。超前進角における角度分布もまたこのような巨大共鳴の研究にとって重要である。今回の研究開発実験で、著しく鮮明なスペクトルが400MeVのアルファ散乱の2度から5度の散乱角において得られた。