Z. Phys. A 349, 3M (1994) Short note ZEITSCHRIFT FURPHYSIKA 9 Springer-Verlag 1994 First observation of low lying states in the doubly odd nucleus 132pr from beta decay of 13ZNd D. Bucurescu 1,2, D. Barn6oud 1, R. B6raud 3, G. Cata-Danil 1,2, T. von Egidy 1,,, A. Emsallem 3, J. Genevey 1, A. Gizon 1, J. Gizon, C.F. Liang 4, P. Paris 4, C.A. Ur 1,2, B. Weiss 1,** t Institut des Sciences NuclSaires, IN2P3-CNRS/Universit~ Joseph Fourier, F-38026 Grenoble Cedex, France 2 Institutul de Fizica Atomica, P.O. Box MG-6, R-769000 Bucharest, Romania 3 Institut de Physique Nucl6aire, IN2P3-CNRS/Universit5 Claude Bernard, F-69621 Villeurbanne Cedex, France 4 CSNSM, IN2P3-CNRS, Bt.104, F-91405 Campus-Orsay, France Received: 16 May 1994 Abstract: the low-lying level scheme of the odd-odd nucleus ~ 500 132pr has been investigated for the first time . The radioactive z Z nuclei were produced by bombarding 96Mo targets with 225 Me V <~ 450 49 Ca beam. Levels have been populated from the 132Nd B-decay. o A new value of its half-life has been measured: T1/2=88~=7 s. ~ 400 The mass identification has been made with an ion-guide cou- o pled with an on-line isotope separator. "I-if-t, X-7-t and e--7-t ~ 550 coincidence measurements have been performed. The observed distribution of the level feedings is similar to that of the neigh- 300 bouring odd-odd nuclei. 250 PA CS: 23.20.Lv, 27. 600+j The only existing spectroscopic information on the 13Zpr nucleus comes from in-beam heavy-ion work [1] and consists of several high-spin bands. Their spin values were tentatively as- signed on the basis of systematics and comparisons with cranked shell model calculations. Y~rom the study of the fl+/EC decay of 13~pr towards states in 13~Ce, one expects two beta-decaying states in 132pr, one with presumable spin-parity (5 +) and the other with a lower spin [2, 3]. Previous measurements on mass separated reaction products in the 1~ reaction provided a half-life of 105• s for 132Nd but gave no indication on any 7-ray transitions in 132pr [4]. The purpose of the present work is to present a detailed study of the beta decay of 132Nd to states in 132Pro Since the ground state of la2Nd is 0 +, the states primarily populated in 132pr will have low spin values (smaller than or equal to 2). Our measurements were performed at the SARA accelera- tor in Grenoble. The radioactive nuclei have been produced by bombarding 98% isotopically enriched 96Mo targets (2mg/cm 2) with a 49Ca beam of 225 MeV. Mass identification measure- ments have been undertaken with an ion-guide coupled to the SARA on-line isotope separator [5]. Gamma-ray spectra in co- incidence with fl-particles detected with a plastic detector have been measured for A=132. In this way the first assignment of the 7-rays associated with the f~+/EC decay of 132Nd to levels in la2pr was made (Fig. 1). A He-jet system has been used to transport the activity in a low background site. With PbC12 at 420 ~ as aerosols, the transport efficiency reached about 60%. *Permanent address: Physik Department~ Technische Universit~t Mfinchen, D-85748 Garching,Germany **Permanent address: Laboratoire de Radiochimie, Universit6 de Nice~ F-06034 Nice-Cedex, France 200 150 100 50 0 < I x ~.) o,_ ~176 (225MeV) A=t32 0 200 400 600 800 1000 CHANNEL NUMBER Fig. 1. fl-gated 7 spectrum measured during 10 hours for mass A=132 with 100 s collection time. Using the He:jet and tape driver systems, the collected ac- tivity was transported between a Ge or X-ray detector and an electron guide for conversion electron measurements. Singles electron and 7(X) spectra ,as well as e--7(X)-t coincidences have been recorded. The electron guide used in these measure- ments is a newly conceived device [6]; consisting of a special 60 cm long coil which produces, within a cylindrical cavity, a continuously increasing field along its length. This design of magnetic lens has a large efficiency (,-~2%) on a wide electron energy range. In the present experiments, to reduce the con- tinuous positron background, the Si(Li) detector was placed within a BGO shield operating in anticoincidence mode. Singles and multianalysis 7 spectra, 7-7-t and X-7-t coin- cidences have been recorded. The singles 7-ray spectra were rather complex due to the presence of many reaction products from both the target and Havar entrance window of the reac- tion chamber.The contributions of all contaminants have been carefully evaluated. The 7-rays assigned to 132pr which appear in the spectrum gated by the K,~ X-rays of Pr have been used to establish the level scheme shown in Fig. 2. The average half