Isoscalar monopole and dipole excitations of cluster states and giant resonances in 12C
Isoscalar monopole and dipole excitations of cluster states and giant resonances in 12C
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DOI：
10.1103/physrevc.93.054307
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发表时间：
2016-05-05
影响因子：
3.1
通讯作者：
Kanada-En'yo, Yoshiko
中科院分区：
文献类型：
--
作者：
Kanada-En'yo, Yoshiko
用位移反对称分子动力学（AMD）和3 α-集团生成坐标（GCM）方法研究了C-12分子的等激子（ISM）和偶极（ISD）激发.小振幅的振动模式所描述的相干单粒子一个空穴激发表示的单核高斯波函数的一个小的移位内的AMD框架，而大振幅的集群模式被纳入通过叠加3 α-集群波函数的GCM。角动量投影和宇称投影在微观上考虑了内禀坐标系中激发与转动和宇称变换的耦合。本文计算了较宽能量范围内的ISM和ISD激发，包括低能区的团簇模和高能区的巨共振，但对高能区的定量描述并不令人满意。α团簇之间的距离运动增强了团簇模的低能ISM和ISD强度，α团簇的角运动使它们分裂成几个态。低能ISM强度耗尽了能量加权和规则的26%，这与通过（e，e '）、（alpha，alpha'）和（Li-6，Li-6 '）散射测量的12 C（0（2）（+）; 7.65 MeV）和C-12（0（3）（+）; 10.3 MeV）的实验数据一致。在计算的低能ISD强度中，在E = 10-15 MeV范围内得到了两个具有显著强度的1（-）态（1（1）（-）和1（2）（-）态）。结果表明，ISD激发可以作为一个很好的探针，在实验上寻找新的团簇态，如C-12（1（2）（-））在本计算中得到的。
The isoscalar monopole (ISM) and dipole (ISD) excitations in C-12 are investigated theoretically with the shifted antisymmetrized molecular dynamics (AMD) plus 3 alpha-cluster generator coordinate method (GCM). The small-amplitude vibration modes are described by coherent one-particle one-hole excitations expressed by a small shift of single-nucleon Gaussian wave functions within the AMD framework, whereas the large-amplitude cluster modes are incorporated by superposing 3 alpha-cluster wave functions in the GCM. The coupling of the excitations in the intrinsic frame with the rotation and parity transformation is taken into account microscopically by the angular-momentum and parity projections. The present a calculation that describes the ISM and ISD excitations over a wide energy region covering cluster modes in the low-energy region and the giant resonances in the high-energy region, although the quantitative description of the high-energy part is not satisfactory. The low-energy ISM and ISD strengths of the cluster modes are enhanced by the distance motion between alpha clusters, and they split into a couple of states because of the angular motion of alpha clusters. The low-energy ISM strengths exhaust 26% of the energy-weighted sum rule, which is consistent with the experimental data for the 12C(0(2)(+); 7.65 MeV) and C-12(0(3)(+); 10.3 MeV) measured by (e, e'), (alpha, alpha'), and (Li-6, Li-6') scatterings. In the calculated low-energy ISD strengths, two 1(-) states (the 1(1)(-) and 1(2)(-) states) with the significant strengths are obtained over E = 10-15 MeV. The results indicate that the ISD excitations can be a good probe to experimentally search for new cluster states such as the C-12(1(2)(-)) obtained in the present calculation.