Observation of isoscalar and isovector dipole excitations in neutron-rich 20O

被引：25

作者：

Nakatsuka, N. ^{[1
,2
]}

Baba, H. ^{[2
]}

Aumann, T. ^{[3
,4
]}

Avigo, R. ^{[5
,6
]}

Banerjee, S. R. ^{[7
]}

Bracco, A. ^{[5
,6
]}

Caesar, C. ^{[3
,4
]}

Camera, F. ^{[5
,6
]}

Ceruti, S. ^{[5
,6
]}

Chen, S. ^{[2
,8
,9
]}

Derya, V. ^{[10
]}

Doornenbal, P. ^{[2
]}

Giaz, A. ^{[5
,6
]}

Horvat, A. ^{[3
,4
]}

Ieki, K. ^{[11
]}

Inakura, T. ^{[12
]}

Imai, N. ^{[13
]}

Kawabata, T. ^{[1
]}

Kobayashi, N. ^{[14
]}

Kondo, Y. ^{[15
]}

Koyama, S. ^{[14
]}

Kurata-Nishimura, M. ^{[2
]}

Masuoka, S. ^{[13
]}

Matsushita, M. ^{[13
]}

Michimasa, S. ^{[13
]}

Million, B. ^{[5
]}

Motobayashi, T. ^{[2
]}

Murakami, T. ^{[1
]}

Nakamura, T. ^{[15
]}

Ohnishi, T. ^{[2
]}

Ong, H. J. ^{[16
]}

Ota, S. ^{[13
]}

Otsu, H. ^{[2
]}

Ozaki, T. ^{[15
]}

Saito, A. ^{[15
]}

Sakurai, H. ^{[2
,14
]}

Scheit, H. ^{[3
]}

Schindler, F. ^{[3
,4
]}

Schrock, P. ^{[3
]}

Shiga, Y. ^{[2
,11
]}

Shikata, M. ^{[15
]}

Shimoura, S. ^{[13
]}

Steppenbeck, D. ^{[2
]}

Sumikama, T. ^{[2
]}

Syndikus, I. ^{[3
,4
]}

Takeda, H. ^{[2
]}

Takeuchi, S. ^{[2
]}

Tamii, A. ^{[16
]}

Taniuchi, R. ^{[14
]}

Togano, Y. ^{[15
]}

机构：

[1] Kyoto Univ, Dept Phys, Kyoto 6068502, Japan

[2] RIKEN, Nishina Ctr, Saitama 3510198, Japan

[3] Tech Univ Darmstadt, Inst Kernphys, D-64289 Darmstadt, Germany

[4] GSI Helmholtzzentrum Schwerionenforsch GmbH, D-64291 Darmstadt, Germany

[5] Ist Nazl Fis Nucl, Sez Milano, I-20133 Milan, Italy

[6] Univ Milan, Dipartimento Fis, I-20133 Milan, Italy

[7] Variable Energy Cyclotron Ctr, 1-AF, Kolkata 700064, India

[8] Peking Univ, Sch Phys, Beijing 100871, Peoples R China

[9] Peking Univ, State Key Lab Nucl Phys & Technol, Beijing 100871, Peoples R China

[10] Univ Cologne, Inst Kernphys, D-50937 Cologne, Germany

[11] Rikkyo Univ, Dept Phys, Tokyo 1718501, Japan

[12] Niigata Univ, Dept Phys, Niigata 9502181, Japan

[13] Univ Tokyo, Ctr Nucl Study, Tokyo 1130033, Japan

[14] Univ Tokyo, Dept Phys, Tokyo 1130033, Japan

[15] Tokyo Inst Technol, Dept Phys, Tokyo 1528551, Japan

[16] Osaka Univ, Res Ctr Nucl Phys, Osaka 5670047, Japan

来源：

PHYSICS LETTERS B | 2017年 / 768卷

关键词：

O-20; Low-energy dipole excitation; Inelastic alpha scattering; Virtual-photon excitation; STRENGTH; CA-40; SPECTROSCOPY; RESONANCE; STATES; BEAMS;

D O I：

10.1016/j.physletb.2017.03.017

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

The isospin characters of low-energy dipole excitations in neutron-rich unstable nucleus O-20 were investigated, for the first time in unstable nuclei. Two spectra obtained from a dominant isovector probe (O-20 + Au) and a dominant isoscalar probe (O-20 + alpha) were compared and analyzed by the distorted-wave Born approximation to extract independently the isovector and isoscalar dipole strengths. Two known 1(-) states with large isovector dipole strengths at energies of 5.36(5) MeV (1(1)(-)) and 6.84(7) MeV (1(2)(-)) were also excited by the isoscalar probe. These two states were found to have different isoscalar dipole strengths, 2.70(32)%(1(1)(-)) and 0.67(12)%(1(2)(-)), respectively, in exhaustion of the isoscalar dipole-energy-weighted sum rule. The difference in isoscalar strength indicated that they have different underlying structures. (C) 2017 The Author(s). Published by Elsevier B.V.

引用

页码：387 / 392

页数：6

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