Z. Phys. A 347, 285-286 (1994) Short note ZEITSCHRIFT FURPHYSIKA 9 Springer-Verlag 1994 Transitional quadrupole moments in 83y T.D. Johnson 1, F. Cristancho 1'**, C.J. Gross ~'***, M. Kabadiyski 1, K.P. Lieb 1, D. Rudolph 1, M. Weiszflog 1, T. Burkardt 2, J. Eberth 2, S. Skoda 2'**** l II. Physikalisches Institut, Universitfit GSttingen, Bunsenstrasse 7-9, D-37073 G6ttingen, Germany 2 Institut ffir Kernphysik der Universitfit zu KSln, D-50937 K61n, Germany Received: 19 October 1993/Revised version: 10 December 1993 Abstract: Doppler shift attenuation lifetime measure- ments have been carried out for the 3qp and isomeric ro- tational bands in S3y using the reaction ~SNi(2Ssi,3p). While the transitional quadrupole moments in the 3qp bands are slightly lower than in the lqp bands, we found evidence for a strong reduction in IQt[ for the isomeric band. PACS :21.60.Ev; 27.50.+e Recent work [1-4] on the S3y isotope has revealed interesting insights concerning interplay between collec- tive and single particle behavior in the mass 80 region. In the first in-beam study [1] of s3y, several rotational sequences were found. The positive-parity yrast band exhibited a bandcrossing interpreted [4] as being due to g9/2 neutron alignment. The negative parity favored signature sequence forked into two separate bands. The bandcrossing in the yrast band was interpreted as a pro- ton alignment. The second branch of this forking had a rotational structure feeding into the 62 ps lived 17/2~- state. We shall refer to this band as an isomeric band. Between the isomeric band and the yrast negative parity band were seen no cross transitions, in spite of the near degeneracy in energies. G-factor measurements [3] sug- gested that a complex n-p rotation-aligned configuration was the underlying structure. Lifetime measurements of S3y indicated decreasing [Qt] for the 3qp structure and rather large deformations for the lower spin states in the yrast negative-parity band. But in the isomeric band, except for the 17/2- and 19/2- states, no lifetimes are available. The lifetime measurements have been extended us- ing the Doppler-shift attenuation method. The reaction used was 5SNi(2ssi,3p)SaY at 95. MeV using the Cologne tandem accelerator. The target was an 99.8 % enriched 0.38mg/cm 2 thick 5SNi foil. Six Comptou-supressed de- tectors were placed in a ring positioned at 900 and one at 0 ~ relative to the beam axis. Doppler shifted lineshapes were obtained, by observing lines in the 0 ~ detector in coincidence with those at 900 . Transitions investigated are shown in the partial lev- el scheme of S3y in Fig. 1. Lineshapes were analyzed with the code GNOMON [2-5]. Side-feeding was treated as in [2,6]. All lifetimes, together with inferred electro- magnetic properties are given in Table 1. Because of the doublet structure of many 7-ray lines, some relevant de- tails of the DSA analysis are presented. The effective lifetimes of the (41/2 + ) and (37/2 + ) states were nearly (41/2 + ) 9075 1807 (37/2*) t 7468 1488 (33/2+) I 5983 1340 (29/2*) t 4643 1192 25/2+ t 3450 1080 21/2 + ~ 2370 (37/2-) 8071 1288 (33/2-) 6879 (33/2-) I 6783 i I (31/2-) 6334 1177 1220 I c29/2-) I 5503 c29/2-) 1 5363 1342 1162 1177 r (27/2-) i 4992 I 830 1026 1078 (21/2-) t 3315 21/2- + 3308 ~----J91491 942 .;'-~ 19/2- ~ 2888 17/2-909~, 2406 ~5~..4 17/2- 2559~ Fig. 1: Partial level scheme for Say relevent for this work. the same (,-- 0.24 ps) and so an upper limit of 0.10 ps is assigned to the (37/2 +) level. The sidefeeding has the same upper limit. Both cascade- and side-feeding were taken into account in the analysis of the 1340 keV transition. The side-feeding was varied from 0.01 to 0.50 ps; minimum X~ were found for v,] -- 0.08,0.31 ps. Since the side-feeding time for the (37/2 + ) level clear- ly had an upper limit of 0.10 ps, the second minimum (0.31 ps) was excluded since an increase of 0.20 ps in the side-feeding time would be unreasonable [6]. This choice is also consistent with the previous [2] suggestion as to the side-feeding of this state. The lifetime of the (29/2 + ) state had been previously [2] measured to be 0.29 ps. We have redone this analysis using the feeding- corrected lifetime of the (33/2 + ) level for the cascade feeding and side-feeding. Side-feeding was analyzed as with the previous transition, resulting in a side-feeding lifetime of 0.09 ps. Three new lifetimes have been measured for the yrast negative-parity band, up to the (33/2-) level. A coincidence gate set on the 1162 keV line was enough to obtain a reasonable line-shape for the 1177 keV line. Coincidence gates set on lower transitions in the cas- cade resulted in a combination of the two lineshapes