【摘要】 通过对 2 5 2　Cf自发裂变产生的瞬发γ谱的实验研究 ,建立与扩展了丰中子核145 ,147　　La的高自旋态能级图 ,最高自旋态达到 ( 4 1 / 2 + )与 ( 4 3/ 2 - ) .测得的交叉相联的相反宇称带及带间的强化E1跃迁说明在 145 ,147　　La中形成强的八极形变 .对145 La的研究表明 ,具有轴对称形状的四极形变与具有反演不对称形状的八极形变在同一核中产生共存与竞争 .在πh11/ 2 带中观测到的带交叉位于 ω≈ 0 2 6— 0 30MeV附近 ,由推转壳模型计算表明 ,它是由一对i13/ 2 中子的顺排所引起的更多还原

【Abstract】 The level schemes with high spin states in neutron rich 145,147 La nuclei have been established from the study of prompt γ rays emitted in the spontaneous fission of 252 Cf. Many new levels and γ transitions have been idenfified. The highest spin states in both nuclei were expanded up to(41/2 +)and (43/2 -)respectively. The alternating parity band structures and strong E 1 transitions between negative and positive parity bands show strong octupole deformation. The collective bands observed in 145 La give evidence for co existence and competition between symmetric and asymmetric shapes. From the systematic comparison with the neighboring isotones, the s =+i bands in both nuclei most probably originate from the single particle π h 11/2 orbital coupling with the neighboring even even cores, respectively. Band crossing of the π h 11/2 bands was found around ω ≈0 26—0 30MeV and these backbends are related to the alignment of two i 13/2 neutrons from cranked shell model calculations.更多还原