On the two-quasineutron rotational band in 128Ba

✍ Scribed by P. Petkov; A. Dewald; R. Kühn; R. Peusquens; D. Tonev; S. Kasemann; K.O. Zell; P. von Brentano; D. Bazzacco; C. Rossi-Alvarez; G. de Angelis; S. Lunardi; P. Pavan; D.R. Napoli

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 285 KB
• Volume: 674
• Category: Article
• ISSN: 0375-9474
• DOI: 10.1016/s0375-9474(00)00173-1

✦ Synopsis

The lifetimes of five levels of the two-quasineutron band in 128 Ba populated via the 116 Cd( 16 O, 4n) reaction were measured for the first time by means of the recoil-distance Doppler-shift method. For the data-analysis, a new version of the differential decay-curve method in singles-like mode was developed which takes into account the velocity distribution of the recoils and the effect of the Dopplershift attenuation in the stopper. The high values of K 2 and K eff characterising the band are confirmed by the determined B(E2, I → I -2) and B(M1, I → I -1) transition strengths. At the same time, the rigid-rotor model is not able to describe the behaviour of the experimental B(E2, I → I -1) and B(M1, I → I -1) values. A new theoretical effort seems to be needed for a consistent explanation of the intraband transition strengths within two-quasiparticle bands in γ -soft nuclei.