High-spin yrast isomer in theN=83151Er nucleus

An highspin yrast isomer (T_1/2 ? 420ns, E>10.286 MeV, 67/2≤ I≤ 71/2) is observed in the¹⁵¹Er nucleus excited in the¹¹⁶ Sn+⁴⁰ Ca reaction, using the recoil shadow method.     

超形变核149Tb中的旋称伙伴带

系统分析了149Tb中的5条超形变带,在对跃迁能量进行光滑化处理后,采用ab拟合或改进的ab拟合,确切地指定了它们的自旋值,其,24和3,5两带都分别构成旋称伙伴带,根据它们的脱耦合常数值,指认了149Tb费米面附近相应的Ω＝1／2单粒子态。     

Magnetic moment of the fragmentation-aligned 61Fe (9/2(+)) isomer

We report on the g factor measurement of an isomer in the neutron-rich (61)(26)Fe (E(*)=861 keV and T(1/2)=239(5) ns). The isomer was produced and spin aligned via a projectile-fragmentation reaction at intermediate energy, the time dependent perturbed angular distribution method being used for the measurement of the g factor. For the first time, due to significant improvements of the experimental technique, an appreciable residual alignment of the nuclear spin ensemble has been observed, allowing a precise determination of its g factor, including the sign: g=-0.229(2). In this way we open the possibility to study moments of very neutron-rich short-lived isomers, not accessible via other production and spin-orientation methods.     

Proton alignment in the 21/2+ yrast state of89Mo

The magnetic moment of the isomeric 2584 keV 21/2⁺ yrast state in⁸⁹Mo was measured via the time differential perturbed angular distribution method after recoil implantation (IMPAD) into a polarized Ni target. A g-factor of +0.79(4) was extracted, indicating a (g _9/2)² v(g _9/2)^–1 structure of this state. The result is placed in a systematic survey of g-factors in this mass region as well as compared with the prediction of shell model calculations.Communicated by: D. Schwalm     

Seniority-three yrast states in theN=82 nucleus147Tb

Firm spin-parity assignments for the high-spin states up to 3.5 MeV in the one-proton nucleus¹⁴⁷Tb were obtained from¹⁴⁴Sm(⁶Li, 3n) in-beamγ-ray and conversion electron measurements. The energies of these two-particle one-hole excitations were calculated from the shell model with empirical nucleon-nucleon interaction energies. The calculated energy splittings agree well with experiment, whereas the theoretical excitation energies disagree by ?1 MeV if recently measured ground state masses are used.     

Identification of the 13/2+ isomer in 199At

The 13/2⁺ isomeric state in the ¹⁹⁹At nucleus has been identified at an excitation energy of 573 keV and its half-life measured to be 580(130) ns using the recoil-decay tagging technique. Received: 19 September 2000 / Accepted: 1 November 2000     

Magnetic moment of the 19/2+ isomer in135Ce

Employing the time-integral PAC technique with an external magnetic field, the g-factor of the 19/2⁺ state at 2,125.6 keV in¹³⁵Ce was determined to be g=?0.07(1). This value favours a predominant (h ₁₁ ^2/?2 s ₁ ^2/?1 ) neutron configuration for this level. Its meanlife has been redetermined with improved precision to be τ=11.8(5) ns.     

Gamow-teller strength and particle-phonon states in149Dy from decay of its 11/2− and l/2+ 149Ho parents

Studies of the¹⁴⁹Ho 11/2^? and 1/2⁺ GT-decays using on-line mass separation have established in the N=83¹⁴⁹Dy nucleus the single neutron excitations below 1.8 MeV and members of the νf_7/2×3^? and νf_7/2×2⁺ particle-phonon multiplets. Quantitative analysis of the GT-decay strength to¹⁴⁹Dy 1qp- and 3qp-states is made in terms of the strength values measured in¹⁴⁹Dy₀ and¹⁴⁷Tb_11/2? decay.     

Mean life of the 21/2+ isomer of89Zr

The mean life of the lowest 21/2(⁺ level of⁸⁹Zr has been measured with a pulsed⁷Li beam and the⁸⁵Rb(⁷Li, 3n)⁸⁹Zr reaction. The mean life is τ=7.39 ± 0.23 ns and the reduced transition probability to the 17/2⁺ state isB(E2)=73±2e²fm⁴. The comparison with shell-model predictions requires a large value of the effective chargee _p ≈ 2) to account for the experimental result. The mean life of the 13/2^? state has also been measured and results to be τ=3.22±0.17ns.     

The g-factor and the electric quadrupole moment of the 7/2+ isomer in125Xe

The time differential perturbed angular distribution method (PAD) was used to measure theg-factor and the electric quadrupole interaction in a Cd single crystal for thet _1/2=140 ns,I ^π=7/2⁺ isomer in¹²⁵Xe. Theg-factor isg=+0.264(10) and the quadrupole coupling constante ² Qq/h=122.1 (6) MHz at 552 K. The lifetime of theI ^π=11/2⁺ state was measured to beτ=11.3 (1.1) ps by the recoil distance method (RDM). From an analysis of the spectroscopic data using the triaxial-rotor-plus-particle (TRPP) model the quadrupole moment of the 7/2⁺ isomer is deduced to beQ=1.40 (15) b yielding an electric field gradient (efg)eq=3.6(4)·10¹⁷ V/cm² for XeCd.     

Theg-factor of the Iπ=5/2+ isomer in77Br

The g-factor of the t_1/2=9.3 ns, I_π=5/2 + state at E_x=130 keV in⁷⁷Br has been measured by observation of the time differential perturbed angular correlation (PAC) in a Co single crystal. The experimental value g=1.32(1) gives evidence for large deformation, which is discussed in the framework of triaxial-rotor-plus-particle models.     

The yrast spectroscopy of 209Rn

The yrast spectroscopy of ²⁰⁹Rn has been investigated to an excitation energy of over 7 MeV and to a spin of $\text{51}\text{2}$. The existence of six isomers has been established: $\text{1174}\text{keV}\text{(J}{}^{\mathrm{\pi }}\text{=}\text{13}\text{2}{}^{\mathrm{+}}\text{, τ}{}_{\mathrm{<mtext>m</mtext>}}\text{= 19.3 ± 1.9 μ}\text{s}\text{), 1687}\text{keV}\text{(}\text{19}\text{2}{}^{\mathrm{?}}\text{, 1.0 ± 0.3}\text{ns}\text{), 2419}\text{keV}\text{(}\text{21}\text{2}{}^{\mathrm{+}}\text{, 12.6 ± 0.3}\text{ns}\text{20 ± 3}\text{ns}\text{, 3637}\text{keV}\text{(}\text{35}\text{2}\text{, 4.3 ± 0.4 μ}\text{s}\text{)}\text{and}\text{4834}\text{keV}\text{(}\text{41}\text{2}{}^{\mathrm{?}}\text{, 14.4 ± 0.5}\text{ns}\text{)}$. Shell-model calcu are used to explain the observed structure. E3 and M2 transitions in ²⁰⁹Rn and neighbouring nuclei are discussed.     

A new sequence of high-spin states built on the 17/2+ isomer in85Kr

High-spin states in⁸⁵Kr have been studied via in-beam spectroscopy by bombarding a⁸²Se target with 32 MeV⁷Li ions. Since⁸⁵Kr is only formed with a small relative cross section proton-— coincidence techniques have been applied to enhance the rays of⁸⁵Kr, even with respect to those of⁸⁶Kr, in the measurements. A new sequence of high-spin states with excitation energies up to 4.8 MeV and tentative spins up to (23/2) has been established on top of the 17/2⁺ s isomer. A tentative assignment of the configurationvg ₉ ^2/–1 (g _9/2 p ₃ ^2/–1 orf ₅ ^2/–1 ) to the new levels is proposed.Supported by Deutsche Forschungsgemeinschaft     

Electron paramagnetic resonance of 61Ni+ in CuGaS2

EPR of ⁶¹Ni⁺ doped CuGaS₂ at 4.2 K leads to the following experimental data: $\text{g = 1.918 ± 0.006 A  < 12 × 10}{}^{-4}\text{cm}{}^{-1}\text{, g}{}_{\mathrm{\perp }}\text{= 2.328±0.006 A}{}_{\mathrm{\perp }}\text{= (65±2) × 10}{}^{-4}\text{cm}{}^{-1}$. High axial field splitting of ²T₂ state stabilizes the center against Jahn-Teller interaction. Covalency reduction factor k is 0.76.     

The magnetic moment of the 19/2− isomer in85Rb

The magnetic moment of the 19/2⁻ isomer in⁸⁵Rb has been measured by means of the TDPAD method providing μ=+1.3(4)μ_N. From this value the dominating three-quasiparticle structure πp _3/2 ⁻¹ pg _9/2 ⁻² has been deduced for this state.     

Nuclearg-factors of theJ π=21/2+isomer in112In and theJ π=6+ 112Sn

Theg-factor of theJ ^π=21/2⁺ isomeric state in¹¹¹In (T _1/2=13.3 ns) and of theJ ^π=6⁺ isomeric state in¹¹²Sn (T _1/2=13.7 ns) were measured using the spin rotation method. The result obtained for theJ ^π=21/2⁺ level in¹¹¹In,g=+0.47 (2), indicates that this state has an almost pure ((πg _9/2)^?1 νg _7/2 νd _5/2) shell model configuration. The experimental valueg=+0.04 (3) for theJ ^π=6⁺ isomer in¹¹²Sn agrees with the theoretical value calculated within the frame of the BCS model.