학술논문
Observation of isoscalar and isovector dipole excitations in neutron-rich 20O
Document Type
article
Author
N. Nakatsuka; H. Baba; T. Aumann; R. Avigo; S.R. Banerjee; A. Bracco; C. Caesar; F. Camera; S. Ceruti; S. Chen; V. Derya; P. Doornenbal; A. Giaz; A. Horvat; K. Ieki; T. Inakura; N. Imai; T. Kawabata; N. Kobayashi; Y. Kondo; S. Koyama; M. Kurata-Nishimura; S. Masuoka; M. Matsushita; S. Michimasa; B. Million; T. Motobayashi; T. Murakami; T. Nakamura; T. Ohnishi; H.J. Ong; S. Ota; H. Otsu; T. Ozaki; A. Saito; H. Sakurai; H. Scheit; F. Schindler; P. Schrock; Y. Shiga; M. Shikata; S. Shimoura; D. Steppenbeck; T. Sumikama; I. Syndikus; H. Takeda; S. Takeuchi; A. Tamii; R. Taniuchi; Y. Togano; J. Tscheuschner; J. Tsubota; H. Wang; O. Wieland; K. Wimmer; Y. Yamaguchi; K. Yoneda; J. Zenihiro
Source
Physics Letters B, Vol 768, Iss C, Pp 387-392 (2017)
Subject
Language
English
ISSN
0370-2693
1873-2445
1873-2445
Abstract
The isospin characters of low-energy dipole excitations in neutron-rich unstable nucleus 20O were investigated, for the first time in unstable nuclei. Two spectra obtained from a dominant isovector probe (O20+Au) and a dominant isoscalar probe (O20+α) 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 (11−) and 6.84(7) MeV (12−) were also excited by the isoscalar probe. These two states were found to have different isoscalar dipole strengths, 2.70(32)% (11−) and 0.67(12)% (12−), respectively, in exhaustion of the isoscalar dipole-energy-weighted sum rule. The difference in isoscalar strength indicated that they have different underlying structures.