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arXiv 2202.00722nucl-ex
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Ca同位素链中等熵巨共振的演化

Evolution of the isoscalar giant monopole resonance in the Ca isotope chain

S. D. Olorunfunmi, R. Neveling, J. Carter, P. von Neumann-Cosel, I. T. Usman, P. Adsley, A. Bahini, L. P. L. Baloyi, J. W. Brümmer, L. M. Donaldson, H. Jivan, N… 展开作者

S. D. Olorunfunmi, R. Neveling, J. Carter, P. von Neumann-Cosel, I. T. Usman, P. Adsley, A. Bahini, L. P. L. Baloyi, J. W. Brümmer, L. M. Donaldson, H. Jivan, N. Y. Kheswa, K. C. W. Li, D. J. Marín-Lámbarri, P. T. Molema, C. S. Moodley, G. G. O'Neill, P. Papka, L. Pellegri, V. Pesudo, E. Sideras-Haddad, F. D. Smit, G. F. Steyn, A. A. Aava, F. Diel, F. Dunkel, P. Jones, V. Karayonchev

摘要:

最近的两项研究的钙同位素链内的等oscillator巨磁共振(ISGMR)的演变报告相互矛盾的结果。一项研究表明,共振能量,从而核$K_{A}$的不可压缩性随质量增加而增加,这意味着核不可压缩性中的不对称项$K_τ$具有正值。另一项研究报告了能量矩的弱下降趋势,导致$K_τ$的普遍接受负值。一个独立的测量的中心区域的ISGMR的Ca同位素链,以获得更好地了解可能的系统性趋势的起源。在南非iThemba实验室的K600磁谱仪中,对在小散射角(包括0 $^\circ$)下观察到的来自一系列钙靶($\mathrm{^{40,42,44,48}Ca}$)的非弹性散射$α$颗粒进行动量分析。单极强度跨越9.5和25.5兆电子伏之间的激发能量范围内获得使用的差异谱(DoS)技术。$^{40,42,44}$ Ca的$E0$强度分布的结构与先前的测量结果吻合良好,该测量结果支持能量矩的弱下降趋势,而在$^{48}$ Ca的情况下没有两个数据集一致。尽管从不同的研究$E0$强度分布的结构特征的变化,我们发现所有的数据集的力矩比,从ISGMR强度计算的激发能量范围内,定义的主共振区域,显示在最好的只有一个弱的系统灵敏度的质量增加。在核不可压缩性中观察到的不同趋势是由主共振区域之外的$E0$强度的贡献引起的,特别是对于高激发能。

英文摘要:

Two recent studies of the evolution of the isoscalar giant monopole resonance (ISGMR) within the calcium isotope chain report conflicting results. One study suggests that the monopole resonance energy, and thus the incompressibility of the nucleus $K_{A}$ increase with mass, which implies that $K_τ$, the asymmetry term in the nuclear incompressibility, has a positive value. The other study reports a weak decreasing trend of the energy moments, resulting in a generally accepted negative value for $K_τ$. An independent measurement of the central region of the ISGMR in the Ca isotope chain is provided to gain a better understanding of the origin of possible systematic trends. Inelastically scattered $α$ particles from a range of calcium targets ($\mathrm{^{40,42,44,48}Ca}$), observed at small scattering angles including 0$^\circ$, were momentum analyzed in the K600 magnetic spectrometer at iThemba LABS, South Africa. Monopole strengths spanning an excitation-energy range between 9.5 and 25.5 MeV were obtained using the difference-of-spectra (DoS) technique. The structure of the $E0$ strength distributions of $^{40,42,44}$Ca agrees well with the results from the previous measurement that supports a weak decreasing trend of the energy moments, while no two datasets agree in the case of $^{48}$Ca. Despite the variation in the structural character of $E0$ strength distribution from different studies, we find for all datasets that the moment ratios, calculated from the ISGMR strength in the excitation-energy range that defines the main resonance region, display at best only a weak systematic sensitivity to a mass increase. Different trends observed in the nuclear incompressibility are caused by contributions to the $E0$ strength outside of the main resonance region, and in particular for high excitation energies.

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