Hurst A M, Butler P A, Jenkins D G, Delahaye P, Wenander F, Ames F, Barton C J, Behrens T, Bürger A, Cederkäll J, Clément E, Czosnyka T, Davinson T, de Angelis G, Eberth J, Ekström A, Franchoo S, Georgiev G, Görgen A, Herzberg R-D, Huyse M, Ivanov O, Iwanicki J, Jones G D, Kent P, Köster U, Kröll T, Krücken R, Larsen A C, Nespolo M, Pantea M, Paul E S, Petri M, Scheit H, Sieber T, Siem S, Smith J F, Steer A, Stefanescu I, Syed N U H, Van de Walle J, Van Duppen P, Wadsworth R, Warr N, Weisshaar D, Zielińska M
Oliver Lodge Laboratory, University of Liverpool, Liverpool L69 7ZE, United Kingdom.
Phys Rev Lett. 2007 Feb 16;98(7):072501. doi: 10.1103/PhysRevLett.98.072501. Epub 2007 Feb 15.
Using a method whereby molecular and atomic ions are independently selected, an isobarically pure beam of 70Se ions was postaccelerated to an energy of 206 MeV using REX-ISOLDE. Coulomb-excitation yields for states in the beam and target nuclei were deduced by recording deexcitation gamma rays in the highly segmented MINIBALL gamma-ray spectrometer in coincidence with scattered particles in a silicon detector. At these energies, the Coulomb-excitation yield for the first 2+ state is expected to be strongly sensitive to the sign of the spectroscopic quadrupole moment through the nuclear reorientation effect. Experimental evidence is presented here for a prolate shape for the first 2+ state in 70Se, reopening the question over whether there are, as reported earlier, deformed oblate shapes near to the ground state in the light selenium isotopes.
采用一种能独立选择分子离子和原子离子的方法，利用REX - ISOLDE将一束等压纯的70Se离子后加速至206 MeV的能量。通过在高度分段的MINIBALL伽马射线光谱仪中记录去激发伽马射线，并与硅探测器中散射的粒子符合测量，推导出束流和靶核中各态的库仑激发产额。在这些能量下，通过核重新取向效应，预计第一激发2+态的库仑激发产额对光谱四极矩的符号会有强烈的敏感性。本文给出了70Se中第一激发2+态为长椭球形的实验证据，再次引发了关于轻硒同位素基态附近是否如早期报道那样存在变形扁球形的问题。
