Isovector giant resonances studied by the (^7Li, ^7Be-gamma) reaction

通过 (^7Li, ^7Be-gamma) 反应研究等向量巨共振

• 批准号: 06452032
• 负责人: NAKAYAMA Shintaro
• 金额: $ 4.67万
• 依托单位: Faculty of Integrated Arts and Sciences, The University of Tokushima
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1994
• 资助国家: 日本
• 起止时间: 1994 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06452032/
• 关键词: charge exchange reaction; isovector resonance; relative spin-strength; effective nuclear interaction; spin-flip transition; non spin-flip transition; スピン-アイソスピン応答; 巨大共鳴

This project aims at studying isovector giant resonances via the (7Li, 7Be) reaction at intermediate energies. The (7Li, 7Be) reaction has characteristics to separately derive spin-flip (DELTAS=1) and non spin-flip (DELTAS=0) isovector excitations by measuring gamma-rays in coincidence with 7Be-ejectiles. Measurement of both DELTAS=0 and DELTAS=1 spectra under the same kinematical condition is expected to provide direct evidence of isovector resonances with DELTAS=0 and DELTAS=1, their relative strength distribution, and nuclear spin-isospin responses.A new gamma-detector system "NYMPHS" were developed using 22 pieces of GSO scintillator. Feasibility of the NYMPHS for the 7Be-gamma coincidence was investigated in the (7Li, 7Be) reactions on 12C and 90Zr at 65 AMeV.The multi-segmented detector system showed good performance for the 7Be-gamma coincidence measurement. The 7Be gamma-ray were clearly identified by detecting its Doppler effect.We investigated nuclear spin-isospin responses in light nuclei. The (7Li, 7Be) reaction was found to predominantly proceed via one-step reaction process. From the H(7Li, 7Be)n reaction, we got an effective nuclear interaction ratio of Vsigmatau/Vtau at 65 AMeV.The ratio is very consistent with the (p, n) data. Using Vsigmatau/Vtau presently observed, we could get relative spin-stregth which reflects nuclear spin-isospin responses.We conclude that the 7Be-gamma coincidence measurement using the NYMPHS is applicable to the (7Li, 7Be) reaction from light nuclei to medium-heavy nuclei at intermediate energies. This means the (7Li, 7Be) reaction is a unique spin-probe for isovector excitations.

该项目旨在研究中等能量下通过（7 Li，7 Be）反应的等矢量巨共振。（7 Li，7 Be）反应具有通过测量与7 Be-抛射体重合的γ射线分别获得自旋翻转（DELTAS=1）和非自旋翻转（DELTAS=0）等矢量激发的特性。在相同的运动学条件下测量DELTAS=0和DELTAS=1能谱，可以直接提供DELTAS=0和DELTAS=1的等矢量共振、相对强度分布以及核自旋-同位旋响应的证据。在65 AMeV ~（12）C和~（90）Zr的（~ 7 Li，~ 7 Be）反应中，研究了NYMPHS用于~ 7 Be-γ符合测量的可行性。通过探测7 Be γ射线的多普勒效应，我们可以清楚地识别出它。发现（7 Li，7 Be）反应主要通过一步反应过程进行。从H（7 Li，7 Be）n反应中得到了65 AMeV的有效核相互作用比Vsigmatau/Vtau，与（p，n）实验数据非常吻合.利用目前观测到的Vsigmatau/Vtau，我们可以得到反映核自旋-同位旋响应的相对自旋强度，从而得出用NYMPHS进行的~ 7 Be-γ符合测量适用于中能轻核到中重核的（~ 7 Li，~ 7 Be）反应。这意味着（7 Li，7 Be）反应是一个独特的自旋探针的isovector激发。

项目成果

中山信太郎: "World Scientific" Spin-isospin excitation modes through the(7Li,7Be)reaction, 8 (1994)

Shintaro Nakayama：“世界科学”通过 (7Li,7Be) 反应的自旋-同位旋激发模式，8 (1994)

中山 信太郎: "The (^7Li,^7Be) reaction as a spin-probe for isovector excitations" Nuclear Intruments and Methods. (印刷中). (1997)

Shintaro Nakayama：“(^7Li,^7Be) 反应作为等矢量激发的自旋探针”核仪器和方法（出版中）。

S. Nakayama: "Spin-Isospin Excitation Modes through the (^7Li,^7Be-γ) Reaction" TOURS SYSPOSIUM ON NUCLEAR PHYSICS II. 542-549 (1995)

S. Nakayama：“通过 (^7Li,^7Be-γ) 反应的自旋-同位旋激发模式”核物理巡回研讨会 II 542-549 (1995)

S.Nakayama: "Isovector Giant Resonances Studies by the(^7Li,^7Be)Reaction" Nuclear Physics. A577. 183-190 (1994)

S.Nakayama：“(^7Li,^7Be) 反应的等矢量巨共振研究”核物理。

中山信太郎: "The (^7Li,^7Be)reaction as a spin-probe for isovector excitations" Nuclear Instruments and Methods. (印刷中). (1997)

Shintaro Nakayama：“(^7Li,^7Be) 反应作为等矢量激发的自旋探针”核仪器和方法（1997 年出版）。