Rotational bands in the near-drip-line nucleus 128Nd

The even-even nucleus ¹²⁸Nd was studied via in-beam γ-ray spectroscopy using the ⁴⁰Ca + ⁸²Mo reaction at 190 MeV. Two new bands were observed besides the yrast one, that has been extended up to spin 34⁺. Configurations were assigned to the three bands by analysing their rotational properties and by comparison with the neighboring even-even nuclei. Received: 18 July 2001 / Accepted: 25 October 2001     

High-spin states in the deformed 122Ba nucleus

The even-even nucleus ¹²²Ba was studied via in-beam γ-ray spectroscopy using the ⁴⁰Ca + ⁹²Mo reaction at 190 MeV. Five bands were observed, four more that can be found in the literature. Configurations were assigned to the various bands from the comparison with the neighboring even-even nuclei. Received: 10 July 2001 / Accepted: 10 October 2001     

Signature inversion in the yrare band of <Superscript>119</Superscript>Xe

Excited states of the ¹¹⁹Xe nucleus have been studied by using in-beam γ-ray spectroscopy with the ¹⁰⁷Ag ( ¹⁶O, p3n) ¹¹⁹Xe fusion-evaporation reaction at a beam energy of 85 MeV. The level scheme of ¹¹⁹Xe has been derived from γ-γ coincidence and γ-γ angular correlation analyses. We have, for the first time, established the second negative-parity favored and unfavored states built on the 11/2^- state, namely the yrare rotational bands in ¹¹⁹Xe. In contrast to the behavior of the yrast bands where the favored states are lying lower in energy, the yrare favored states were observed to lie above the unfavored band. Such a signature inversion in ¹¹⁹Xe is changed to be normal at I = 12?. Received: 8 January 2002 / Accepted: 18 April 2002     

Nuclear structure in the vicinity of the N = Z line in the A = 90-100 region

Neutron-deficient nuclei in the mass region A≈ 90-100 exhibit a large variety of phenomena. In this region the heaviest N = Z nuclei are identified and enhanced neutron-proton correlations are expected when protons and neutrons occupy identical orbitals. A variety of nuclear shapes are predicted and observed for A? 91, including superdeformed shapes. The nucleus ¹⁰⁰Sn is the heaviest N = Z doubly magic nucleus believed to be bound. Knowledge of the shell structure around ¹⁰⁰Sn is of utmost importance for understanding the nuclear shell model. New results on both the N = Z nucleus ⁸⁸Ru, superdeformed structures in A≈ 90 nuclei as well as the first result on the level structure in ¹⁰³Sn, and an extended level structure in ¹⁰²In are presented. The limitations of using stable beams and targets and the possibilities with new radioactive beams are briefly outlined. Received: 1 May 2001 / Accepted: 4 December 2001     

Terminating high-spin bands in 101Rh

High spin states of ¹⁰¹Rh have been populated using the reaction ⁷⁰Zn+³⁶S at 130 MeV. γ-rays were detected with the EUROGAM2 array. New high-spin bands have been observed in this nucleus up to 45/2⁻, 57/2⁻ and 65/2⁺ states. They have been interpreted using the Nilsson-Strutinsky cranking formalism as terminating configurations. Two of the bands were observed up to the predicted terminating states which are built up from g_9/2 protons as well as d_5/2, g_7/2 and h_11/2 neutrons relative to a ⁹⁰Zr core. Received: 30 October 1998     

Measurement of quadrupole moment of the 134 keV level in <Superscript>131</Superscript>Cs

The time differential as well as time integral perturbed angular correlations of the 486-134 keV cascade in ¹³¹Cs have been studied in a polycrystalline BaSO₄ powder source using a HPGe-BaF₂ detector system. The fundamental quadrupole frequency for the 134 keV level has been found to be ω₀= (4.4 ± 0.4) × 10⁷ rad/s. From a comparison of the quadrupole frequencies of this level and that of the 81 keV level in ¹³³Cs, measured earlier in the same crystalline environment of the source, the absolute value of the quadrupole moment of the 134 keV level in ¹³¹Cs has been found to be 0.022 ± 0.002 b. This value of the quadrupole moment is reported for the first time and compared with the value predicted theoretically within the unified nuclear model with intermediate coupling. Received: 21 October 1999 / Revised version: 22 December 1999     

Candidates for chiral doublet bands in 136Nd

The even-even nucleus ¹³⁶Nd was studied via in-beam γ-ray spectroscopy using the ¹⁶O + ¹²⁵Te reaction at 100 MeV and the EUROBALL array. One new dipole band was observed. Together with a previously identified dipole band, whose position in the level scheme is revised, the new band forms a doublet structure similar to the recently observed chiral bands in the odd-odd neighboring nuclei. This would be the first case of a chiral doublet in an even-even nucleus. Received: 23 May 2002 / Accepted: 30 September 2002 / Published online: 27 November 2002 RID="a" ID="a"e-mail: costel.petrache@unicam.it RID="b" ID="b"Present address: Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA. RID="c" ID="c"Present address: Gesellschaft für Schwerionenforschung D-64291 Darmstadt, Germany. Communicated by C. Signorini     

In-beam spectroscopy of 126Ce and 127Pr

High spin states in ₁₂₆Ce and ₁₂₇Pr were populated via heavy ion reactions with 182-MeV ₃₅Cl projectiles on a thick ₉₆Ru target. Prompt γ–γ coincidences were measured. New states in ₁₂₆Ce and ₁₂₇Pr were found. The results are discussed in the framework of the core–quasiparticle coupling model. Received: 16 June 1998     

Configuration assignments and decay of 126La high-spin bands

High spin states of ¹²⁶La have been populated using the reaction ¹¹⁶Sn+¹⁴N at 68 MeV. γ-rays and conversion electrons were detected with the GAREL array. Multipolarities of the lowest-lying in-band dipole transitions have been determined from the deduced internal conversion coefficients. Experimental B(M1)/B(E2) ratios have been derived for the bands and compared with calculated values using the D?nau-Frauendorf geometrical model. Configurations are proposed for the bands comparing them with cranked shell model calculations and on the basis of the measured B(M1)/B(E2) ratios. The β-decay of ¹²⁶La has also been revisited. The population of the ¹²⁶Ba levels gives a probable spin value of five for the decaying high-spin ¹²⁶La state with T _1/2≈ 64 s which may indicate a signature inversion in the πh_11/2νh_11/2 band. Received: 12 October 1999     

Spectroscopy of the deformed 126Ce nucleus

The even-even nucleus ¹²⁶Ce was studied via in-beam γ-ray spectroscopy using the ⁴⁰Ca + ⁹²Mo reaction at 190 MeV. Five bands were observed, one of them being identified for the first time. New connecting transitions were identified between the bands, which lead to new spin assignments. The bands are discussed in the framework of the IBM + broken pairs model. Received: 17 July 2002 / Accepted: 23 October 2002 / Published online: 18 February 2003 RID="a" ID="a"e-mail: costel.petrache@unicam.it Communicated by C. Signorini     

New excited superdeformed bands in heavy Pb nuclei: Clue for an octupole softness near the N = 118 gap at large deformation

We report the identification of six new superdeformed (SD) bands in ^197,198Pb observed with the EUROBALL IV spectrometer. The results are interpreted in the framework of cranked Hartree-Fock calculations with approximate projection on the particle number by means of the Lipkin-Nogami method. A mixing between quasi-particle excitations and an octupole vibration is suggested in the two SD isotopes. We have estimated the ordering of the neutron valence orbitals and confirm indirectly a N = 118 SD gap. Received: 20 December 2000 / Accepted: 24 January 2001     

Rotational bands in the doubly odd 130Cs nucleus

The band structures built on the 5^- isomeric state ( T _1/2 = 3.46 m) in the doubly odd ¹³⁰Cs nucleus have been established up to I = 24? via the ¹²⁴Sn(¹¹B, 5n)¹³⁰Cs reaction. The previously observed bands based on the πh _11/2⊗νh _11/2, πg _7/2⊗νh _11/2 and πd _5/2⊗νh _11/2 configurations and a positive-parity side band with multiple connections to the α = 0 signature partner of the yrast πh _11/2⊗νh _11/2 band have been extended to higher spins. A new band based on the πh _11/2⊗νg _7/2 configuration is observed. The yrast πh _11/2⊗νh _11/2 band exhibits anomalous signature splitting whose magnitude decreases up to spin 15 and then increases without restoring the normal signature splitting. Received: 20 February 2001 / Accepted: 9 May 2001     

Investigation of the magnetic rotation in 196Pb

Lifetimes for low-lying members of the irregular ΔI = 1 band in ¹⁹⁶Pb have been measured by means of the EUROBALL spectrometer using the coincidence recoil distance technique. The ¹⁶⁴Dy(³⁶S,4n)¹⁹⁶Pb reaction at a beam energy of 168 MeV was used. The data were analyzed with the differential decay-curve method (DDCM). A characteristic drop in the reduced transition probabilities with increasing angular momentum was observed in agreement with predictions by the semiclassical model for the shears mechanism. Received: 3 May 2001 / Accepted: 20 June 2001     

New yrast excited states of the N = 84 nucleus 142Ce observed in deep inelastic reactions

Excited states of ¹⁴²Ce, populated in deep inelastic reactions of ⁸²Se projectiles bombarding ¹³⁹La target, have been studied up to medium spins using in-beam γ spectroscopy techniques. Three new levels have been identified at 2625, 2995, 3834 keV, and assigned as 8⁺, 9^(-) and 11^(-), respectively. These new yrast states follow closely the level systematics of the even mass N = 84 isotones. Their strctures have been discussed with the help of empirical shell model calculations. Received: 2 November 2001 / Accepted: 15 January 2002     

High spin states in 128Ba

High spin states in ¹²⁸Ba have been investigated with the fusion–evaporation reaction ⁹⁶Zr(³⁶S,4n)¹²⁸Ba at a beam energy of 150 MeV with the GASP-spectrometer at INFN in Legnaro, Italy. The level scheme could be extended to higher spins and six-quasiparticle states have been observed. The deduced alignments are compared to the predictions of previously reported cranked shell model calculations. Received: 4 January 1999     

First identification of rotational bands in 103Tc: Evolution of intrinsic proton states of the 97-105 43Tc isotopes

High-spin states of ¹⁰³ ₄₃Tc have been identified for the first time, this nucleus being produced as fission fragment following the fusion reaction ³⁷Cl + ¹⁷⁶Yb at 170 MeV bombarding energy. The high-spin level scheme has been built from the prompt gamma rays detected using the Euroball III array. It exhibits similarities with those of the neighbouring isotopes and isotones. All the band head configurations observed in the ^97-105Tc isotopes are identified from the behaviour of the rotational bands built on them. The single-proton states located around the Fermi level are discussed as a function of deformation of these nuclei. Received: 19 January 2001 / Accepted: 23 February 2001     

Yrare bands of 121Xe

High-spin states in ¹²¹Xe have been studied via the ¹⁰⁹Ag (16O, p3n) ¹²¹Xe reaction at a beam energy of 80 MeV. Several rotational bands based on one- and three-quasiparticle excitations have been established. Among them, an unfavoured yrare rotational band with unfavoured signature has been newly identified. Received: 19 November 1998     

High spin structure of 117I

High-spin states in ¹¹⁷I have been studied via the ¹⁰³Rh(¹⁸O, 4n) reaction at a beam energy of 85 MeV. Many deformed rotational bands built on the proton h_11/2, g_7/2, and g_9/2 orbitals have been identified. Among them, an unfavoured rotational band and a quasi-gamma band based on the h_11/2 state have been newly observed. Moreover, positive-parity states above I^π= 35/2⁺ reported in the previous work have been rearranged. Several energetically favoured states have been assigned to noncollective oblate states based on various quasiparticle configurations with β₂≈ 0.18–0.19 and γ= 60°. Received: 1 March 1999     

Investigation of lifetimes in quadrupole bands of 142Gd

For a level scheme investigation of ¹⁴²Gd an experiment with the γ -spectrometer EUROBALLIII has been carried out and lifetimes have been measured with EUROBALL IV using the Doppler-shift attenuation method. The high-spin states have been populated in these experiments by means of the ⁹⁹Ru(⁴⁸Ti, 2p3n) reaction at a beam energy of 240MeV and the ¹¹⁴Sn(³²S, 2p2n) reaction at 160MeV, respectively. Reduced E2 transition probabilities B(E2) were determined for 15 members of four quadrupole bands. For the interpretation of the positive-parity even-spin quadrupole bands, calculations in the cranked Nilsson-Strutinsky as well as interacting boson models have been performed. From the former calculations it was concluded that the high-spin states of the (+ , 0)₁ band in ¹⁴²Gd represent a triaxial nucleus rotating around the longest principal axis.     

Lifetime measurement of the ((11/2)−) isomer in 125Cs

A new rotational band has been observed in ¹⁶⁷Lu by ¹⁵²Sm (¹⁹F,4n)reaction at the HI-13 tandem accelerator of CIAE in Beijing. The high spin transition energies of the new band are almost identical to the triaxial superdeformed bands recently discovered in ¹⁶³Lu and ¹⁶⁵Lu. This new band is predicted as a triaxial superdeformed band by total routhian surface calculations. Received: 6 October 1997