J. Hattula

Levels in 110Pd, 112Pd, 114Pd and 116Pd from the beta decays of the on-line mass separated Rh isotopes☆

Abstract The energy levels of even 110–116 pd nuclei have been studied from β-decays of odd-odd 110–116 Rh isotopes produced at the on-line isotope separator IGISOL. Two β-decaying states with I π = 1 + and I ⩾4 have been identified in all the cases. New level schemes with preliminary spin assignments have been constructed for 112 Pd, 114 Pd and 116 Pd. Similarities with the level structures of their Xe isotones have been pointed out.

Electromagnetic transition probabilities in 130Ce

Abstract Lifetimes of excited nuclear states have been measured in 130 Ce using the coincidence-plunger technique. The employed nuclear reaction was 98 Mo( 36 S, 4n) 130 Ce at a beam energy of 150 MeV. The measurement has been performed at the NSF Daresbury using the ESSA 30 set-up. It was possible to determine lifetimes for the 4 + to 16 + states in 130 Ce. The experimental B (E2) values could be well reproduced by calculations using the triaxial rotor model with β = 0.26 and γ = 21° as well as the rotation vibration model ( β = 0.25).

In-beam study of 127, 129Xe and collective description of the level structures in odd-A Xe nuclei

Abstract The levels in 127Xe have been studied with the 126Te(3He, 2n) and 128Te(3He, 4n) reactions and in 129Xe with the 130Te(3He, 4n) and 126Te(α, n) reactions using enriched Te targets and inbeam γ-ray and conversion-electron spectroscopic methods. In addition to the h 11 2 level structures, positive-parity bands based on different low-j; states were observed in both nuclei. The observed g 7 2 band head at 342.2 keV in 127Xe is an isomeric state with a half-life of 37 ± 3 ns. Both triaxial-rotor and core-plus-quasiparticle model calculations have been carried out to explain the observed band structures in 123–129Xe. The calculations indicate different shapes for the positive- and negative-parity level systems.

In-beam study of the 128, 130Xe nuclei

Abstract The level structure of 128,130Xe has been studied in the (α, 2nγ) and (3He, 3nγ) reactions on enriched Te targets using in-beam γ-ray spectroscopic methods. For both nuclei the existing information about positive-parity level structure was enriched and many new negative-parity two-quasiparticle states were observed. Isomeric states with the half-lives of 63 ± 12 ns in 128 Xe and 4.8 ± 0.5 ns in 130 Xe were found. For collective positive-parity states the interacting boson model, and calculations based on Bohr hamiltonian were compared with the experimental data.

In-Beam Study of 122,124,126Xe

Excited states in 122,124,126Xe have been studied with the (3He, 3n) reaction using enriched Te targets and in-beam γ-ray and conversion electron spectroscopy. The existing information on the positive-parity levels is enriched and many new negative-parity states are established. A new 7- isomeric state is observed in 126Xe with a half-life of 1.9(5) ns. Interacting boson model (IBA-1) calculations have been performed to explain the collective level structures.

Coexistence of Vibrational and Quasiparticle Structures in Neutron-Deficient 114,115,116,117Te

Excited states in 114-117Te were populated in the bombardment of 114,116Sn targets with 3He ions at energies Elab = 20.9-27.5 MeV. The subsequent de-excitation was studied using in-beam spectroscopic methods, including measurements of γ-ray excitation, γ-γ coincidences, γ-RF timing, γ-ray angular distributions and conversion electrons. States with angular momenta up to J 12 h were observed, but no isomers with T1/2 1 ns were located. The excited structures are discussed in terms of vibrational bands coupled to one- and two-quasiparticle shell-model structures. The systematical behaviour of the excited states in Te isotopes is studied in the mass range A = 115-123 for the odd, and A = 112-134 for the even isotopes.

Lifetimes of yrast states in 110Cd

Abstract Lifetimes or lifetime limits of 20 yrast levels in 110 Cd have been measured using the recoil-distance method and the NORDBALL array of Compton-suppressed Ge detectors. From the reduced transition probabilities competing rotational and vibrational behaviour of 110 Cd is revealed. Also non-collective states, associated with proton configurations, have been observed.

High-spin, discrete line spectroscopy of 162Yb and 164Hf and the systematics of N = 92 isotones

Abstract The high spin states of 162 Yb and 164 Hf have been studied using 122 Sn( 44 Ca, 4n) and 120 Sn( 48 Sn( 48 Ti, 4n) reactions respectively. The resulting new level schemes for 162 Yb and 164 Hf are presented and compared with existing data for 160 Er. The systematic behaviour of these three N = 92 isotones at large angular momentum yields information both on modifications of the single-neutron spectrum of states resulting from the polarisation of the nuclear field and on the single-proton spectrum of states.

High-j bands in 173Ir

Abstract High-spin states in rotational bands associated with the 11 2 − [505] , 1 2 − [541] and 1 2 + [660] Nilsson orbits have been observed in the previously unknown 173Ir nucleus using the 144Sm(32S,p2n) reaction at 163 MeV. The B(M1; I → I − 1)/B(E2; I → I −2) ratios have been extracted for the 11 2 − [505] band and compared with predictions of the semiempirical model by Donau and Frauendorf. The quasineutron band crossing frequencies and alignment gains are discussed in terms of the CSM model. Calculations for equilibrium deformations suggest different deformations for the three bands observed.

Neutron and proton bands in 122Xe at high spins

High-spin bands in 122,123,124Xe and 123Cs were populated using 3He- and 16, 18O-induced reactions on Te, Pd and Ag targets. The subsequent de-excitation was studied using gamma -ray and conversion-electron spectroscopic methods. States with spins up to Jpi =(25-), (35/2-), (21-) and (51/2-), respectively, were identified. In 122Xe four Delta I=2 bands were identified in addition to the ground state and gamma bands, and furthermore a Delta J=1 band with a tentative (K,I)pi =(10, 10)- band head was observed. In 123Xe the previously observed 11/2- and 7/2+ bands were extended to Jpi =(35/-) and (23/2+), respectively. The yrast cascade in 123Cs was extended to spin 51/2-. In 124Xe the recently presented level scheme was completed with some high-lying levels. The band structures were interpreted within the cranked shell model (CSM) framework. A consistent description of band crossing frequencies in both odd and even nuclides was obtained, and configurations were assigned to most of the observed bands. Some relative transition rates were obtained from branching intensities.