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     

Contribution of quasiparticle-phonon,recoil and coriolis interactions in describing low-lying states of <Superscript>133</Superscript>Nd isotope

A quasiparticle-phonon coupling based on one quadrupole phonon is developed. The coupling is constructed by using a deformed average field of Nilsson, a monopole pairing interaction and a quadrupole-quadrupole force. Microscopic structure of the quadrupole phonon is given from the Tamm-Dancoff Approximation. The two effects of recoil and Coriolis forces are included with the assumption of a symmetric rotational motion. Since theoretical treatment is performed for an odd- A nuclei the configuration of intrinsic states should contain both one-quasiparticle and quasiparticle-phonon components. This method is applied to describe the level scheme of ¹³³Nd for which an agreement with experimental data is obtained. The results are also found similar to previous calculations obtained by the Particle plus Triaxial Rotor Model. Received: 23 August 1999     

Spectroscopy of neutron deficient 108Te

The neutron deficient nucleus ¹⁰⁸Te was studied in the ⁵⁴Fe(⁵⁸Ni,2p2n) reaction. A detector system consisting of 4 Euroball cluster detectors, a charged-particle detector ball and a 16 element neutron multiplicity filter was used to detect the emitted particles and γ rays. A new, significantly extended level scheme was constructed on the basis of γγ-coincidence relations. Spin values for the states were determined from angular distribution ratios. The experimental results are discussed in terms of the shell model. Received: 7 September 1998     

Band termination in the Z = N odd-odd nuclei <Superscript>46</Superscript>V and <Superscript>50</Superscript>Mn

The configuration-dependent cranked Nilsson-Strutinsky approach has been employed to study the properties and band structures at high spin in the Z = N odd-odd nuclei ⁴⁶V and ⁵⁰Mn. The observed bands are explained and terminating states are confirmed by the calculations. The calculated and observed bands are in good agreement without normalization, especially for terminating states. Possible bands with rotation around the intermediate axis and the effect of γ-deformation on the total energy of several interesting configurations are discussed. Received: 2 April 2002 / Accepted: 27 January 2003 / Published online: 15 April 2003     

Intruder bands in 113Sn

Abstact: The level structure of ¹¹³Sn has been investigated. The data were obtained by in-beam γ-ray spectroscopy using the reaction ¹⁰⁰Mo(¹⁸O,5n)¹¹³Sn at 70 MeV performed at the OSIRIS gamma array in the Institut für Kernphysik FN Tandem accelerator. We report in this short note the observation of two intruder type rotational bands in this nucleus. Received: 28 April 1998     

Maximally aligned states in 99Ag

Excited states of ⁹⁹Ag were populated via the ⁵⁰Cr + ⁵⁸Ni (261 MeV) reaction using the NORDBALL detector array equipped with charged-particle and neutron detector systems for reaction channel separation. On the basis of the measured γγ-coincidence relations and angular distribution ratios a significantly extended level scheme has been constructed up to E _x ∼ 7.8 MeV and I = 35/2. The experimental results were described within the framework of the shell model. Candidates for states fully aligned in the πg _9/2 ^-3ν(d _5/2, g _7/2)² valence configuration space were found at 4109 and 6265 keV. Received: 18 June 2002 / Accepted: 11 October 2002 / Published online: 4 February 2003 RID="a" ID="a"e-mail: sohler@atomki.hu Communicated by J. ?yst?     

Band structures in 108In

High spin states in ¹⁰⁸In have been established upto ∼ 8 MeV in excitation energy and to a tentative spin of (23⁻). The data were obtained by in-beam γ-ray spectroscopy using the reaction ⁹³Nb(¹⁹F, p3n)¹⁰⁸In at a beam energy of 86 MeV. Four sequences of dipole bands and a normal rotational band of E2 γ-transitions have been placed in the level scheme. Received: 16 June 1998     

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     

Low-lying magnetic dipole strength distribution in the γ-soft even-even 130-136Ba

In this study the scissors mode 1⁺ states are systematically investigated within the rotational invariant Quasiparticle Random Phase Approximation (QRPA) for ^130-136Ba isotopes. We consider the 1⁺ vibrations generated by the isovector spin-spin interactions and the isoscalar and isovector quadrupole-type separable forces restoring the broken symmetry by a deformed mean field according to A.A. Kuliev et al. (Int. J. Mod. Phys. E 9, 249 (2000)). It has been shown that the restoration of the broken rotational symmetry of the Hamiltonian essentially decreases the B(M1) value of the low-lying 1⁺ states and increases the collectivization of the scissors mode excitations in the spectroscopic energy region. The agreement between the calculated mean excitation energies as well as the summed B(M1) value of the scissors mode excitations and the available experimental data of ¹³⁴Ba and ¹³⁶Ba is rather good. A destructive interference between the orbit and spin part of the M1 strength has been found for barium isotopes near the shell closer. For all the nuclei under investigation, the low-lying M1 transitions have ΔK = 1 character as it is the case for the well-deformed nuclei.     

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     

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     

1<Superscript>+</Superscript>(0<Superscript>+</Superscript>) state at 12.4 MeV in <Superscript>20</Superscript>Ne

Careful review of all the evidence makes it clear that at least three states are important at 12.4-MeV excitation in ²⁰Ne (four, if the broad (2⁺) at 12.5 MeV is included). The three states are 3 ^- , 0 ⁺ , and 1 ⁺ (0⁺). The latter, which is quite strong in ¹⁹F (³He, d) singles, is probably the state observed in coincidence with 6.13-MeV γ-rays in ¹⁹F(³He, dγ). Received: 19 August 2002 / Accepted: 28 October 2002 / Published online: 17 January 2003 RID="a" ID="a"e-mail: fortune@physics.upenn.edu Communicated by D. Guerreau     

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     

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     

Five-quasiparticle bands in 127Ba

High spin states in ₁₂₇Ba have been investigated with the fusion–evaporation reaction ₉₆Zr(₃₆S,5n)₁₂₇Ba at a beam energy of 150 MeV with the GASP-spectrometer at INFN in Legnaro, Italy. The level scheme could be extended to high spins resulting in the observation of five-quasiparticle states. Altogether 15 band structures were placed in the level scheme. Received: 3 July 1998     

In-beam studies of very neutron-deficient heavy nuclei

The JYFL gas-filled recoil separator RITU, combined with Ge detector arrays and a SACRED magnetic solenoid spectrometer, has been successfully employed in recoil-decay-tagging (RDT) experiments in order to probe structures of very neutron-deficient heavy nuclei. The present contribution focuses on the light Pb region where the new data extend the systematics of shape-coexisting yrast states towards the proton dripline. Similarities between band structures and their relation to possible multi-particle multi-hole intruder excitations will be discussed. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: rauno.julin@phys.jyu.fi     

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     

High-spin levels in 147Tb

The high-spin states of ¹⁴⁷Tb have been studied with regard to their spins. The data were obtained by in-beam γ-ray spectroscopy using the reaction ¹²⁰Sn(³¹P,4n)¹⁴⁷Tb at 152 MeV performed at the Osiris spectrometer in Berlin. We obtained multipole mixing ratios for 60 transitions, and level spins up to 67/2ħ are introduced. Received: 30 March 1998     

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