Lifetimes and structures of some levels above 1.5 MeV in 168Yb, 164Er and 158, 160, 162Dy

The following lifetime measurements have been performed in ¹⁶⁸Yb: 62 ns (7^?, 2222.5 keV), 0.34ns (6^?, 2111.1 keV), 81.7 ns (5^?, 1998.7 keV), ≦ 0.14 ns (4⁺, 2203.8 keV); in ¹⁶⁴Er: 23.3 ns (7^?, 1985.0 keV), 0.22 ns (6^?, 1744.4 keV), ≦ 0.08 ns (5^?, 1664.2 keV); in ¹⁵⁸Dy: ≦ 0.11 ns (4⁺, 1895.3 keV); in ¹⁶⁰Dy: 0.18 ns (4⁺, 1694.0 keV); in ¹⁶²Dy: 1.93 ns (5^?, 1485.9 keV). The experimental reduced transition probabilities are discussed in the framework of current nuclear models.     

High spin investigation in 193Pb with EUROGAM 2: coexistence of superdeformed and dipole bands

The nucleus ¹⁹³Pb was populated via the ¹⁶⁸Er(³⁰Si, 5n) reaction at a beam energy of 159 MeV and studied with the EUROGAM II spectrometer. Five new dipole ΔI = 1 cascades have been found. The ¹⁹³Pb dipole bands are discussed in terms of microscopic HF+BCS calculations. The proposed configurations are based on a high-K two-quasiproton excitation coupled to rotation aligned quasineutrons. Parallel to the dipole bands the six superdeformed bands have been discussed in the framework of microscopic mean-field calculations. The bands are interpreted as three pairs of signature partners based on quasineutron excitations. Cross-talk transitions linking two signature partner superdeformed bands have been observed and, for the first time in lead isotopes, a mean B(M1)/B(E2) ratio value of 0.15±0.04 μ _N ² /e^2b2 has been extracted.     

Observation of the single step links of the yrast superdeformed band in 194Pb

The EUROGAMarray has been used to investigate the decay out of the yrast superdeformed (SD) band in ¹⁹⁴Pb. Eigth single step decays from the lowest observed SD states to low-lying states at normal deformation (ND) have been identified. From this observation, the excitation energy (4877 ± 1.5 keV) and the spin (6⁺) of the lowest observed SD state in ¹⁹⁴Pb are established.     

Dipole bands and multi-quasiparticle excitations in 193Pb

The nucleus ¹⁹³Pb was populated via the ¹⁶⁸Er(³⁰Si,5n) reaction at a beam energy of 159 MeV and studied with the EUROGAM II spectrometer. Five new dipole Δ I = 1 cascades have been found. These structures have been connected to the level scheme which has been considerably extended up to a spin of ? and an excitation energy of about 8 MeV. Angular distribution coefficients, a₂, have been measured and confirm the dipole character of the in-band transitions. B(M1)/B(E2) ratios have been extracted for the two most intense cascades. The ¹⁹³Pb dipole bands are discussed in comparison with those known in odd lead isotopic series and the structure of the band heads is analyzed in terms of microscopic HF+BCS calculations. The proposed configurations are based on a high-K two quasiproton excitation, π ([505]9/2^t? ? [606]13/2⁺)_K=11^t -, coupled to one or three rotation aligned quasineutrons involving the i_13/2, p _3/2, f_5/2 and/or h{9/2} subshells. The main difference, compared with the heavier lead isotopes, is the presence of large Ω orbitals from the ν (i_13/2) shell near the Fermi surface which are responsible for the increasing band-head spin as A decreases.     

First observation of a superdeformed nucleus produced in an α xn reaction channel

Excited states in the neutron deficient ¹⁴⁵ Dy nucleus have been identified by means of the reaction ¹¹²Sn(³⁵ Cl,pn) at 159 MeV. The level scheme above the 11/2 ^? state and up to spin I～37/2 was obtained using γ-ray spectroscopy methods. The level structure is discussed in terms of the coupling of a h _11/2 neutron hole with the N=80 core excitations.     

Identification and decay of 12s 138Eu

Narrow p,γ resonances have been investigated by using inverse reactions with heavy-ion beams, e.g.¹⁵N,²⁷Al and³⁰Si. The observed line shapes of dominant Gaussian form are due to the vibrational modes of¹H bonded to heavy target atoms.     

Dipole bands and multi-quasiparticle excitations in193Pb

The nucleus¹⁹³Pb was populated via the¹⁶⁸Er(³⁰Si,5n) reaction at a beam energy of 159 MeV and studied with the EUROGAM II spectrometer. Five new dipoleΔI=1 cascades have been found. These structures have been connected to the level scheme which has been considerably extended up to a spin of 61/2? and an excitation energy of about 8 MeV. Angular distribution coefficients,α ₂, have been measured and confirm the dipole character of the in-band transitions. B(M1)/B(E2) ratios have been extracted for the two most intense cascades. The¹⁹³Pb dipole bands are discussed in comparison with those known in odd lead isotopic series and the structure of the band heads is analyzed in terms of microscopic HF-BCS calculations. The proposed configurations are based on a high-K two quasiproton excitation,π([505]9/2^??[606]13/2⁺) _K =11^?, coupled to one or three rotation aligned quasineutrons involving thei _13/2,p _3/2,f _5/2 and/orh _9/2 subshells. The main difference, compared with the heavier lead isotopes, is the presence of largeΩ orbitals from theν (i _13/2) shell near the Fermi surface which are responsible for the increasing band-head spin as A decreases.     

Identification and decay of102In,new neutron deficient isotope close to100Sn

¹⁰²In, [T_1/2=(24±4)s], has been identified for the first time using an on-line mass isotopic separator operating on nuclear reactions induced by heavy ions. Gamma-rays observed both in¹⁰²In→¹⁰²Cd decay and in-beam measurements allow to build a partial level scheme for¹⁰²Cd. Systematics of the two first excited states of even cadmium isotopes shows the special behaviour of the lightest one.     

Beta-decay of even-A neutron-deficient Pr isotopes

Even-A praseodymium activities have been produced and identified in the⁴⁰Ca +^92–96Mo reactions at 5.8 MeV/u:¹²⁶Pr[T_1/2=(3.0 ±0.4)s]¹²⁸Pr[T_1/2=(3.1 ±0.3)s],¹³⁰Pr[T_1/2 =(40.0 ±0.4)s]¹³²Pr[T_1/2=1.6 min]. Several new low-energy levels have been populated in even-even cerium nuclei.