High-K band structures in 164Er

High-spin states of the doubly-odd ¹¹²Sb were studied by in-beam spectroscopy using the ⁸⁸Sr (²⁸Si, p3n) and ⁸⁹Y (²⁹Si, α2n) fusion-evaporation reactions at beam energies of 120 and 108 MeV, respectively. γ?γ, charged particle-γ?γ coincidences, and γ?γ angular correlation analyses were employed for determining the level scheme of ¹¹²Sb. In the present work, all the levels except for low-lying states in ¹¹²Sb were newly established. Two ΔI = 1 strongly coupled bands were observed; one is a negative-parity band that is similar to those observed in the neighboring doubly-odd Sb isotopes and the other is a positive-parity band that has a new type structure not observed in the other isotopes. From the similarity of the properties of these ΔI = 1 bands to the bands built on 9/2⁺ 2p?1h states in the odd-A Sb isotopes, we suggest that these two ΔI = 1 bands should be associated with the [π(g_9/2)^?1 ? νh_11/2] and [π(g_9/2)^?1νg_7/2] configurations, respectively.     

High spin states in lead isotopes with 193<=A<=199

Theγ de-excitation of odd neutron deficient lead isotopes with mass numbers 193–199, produced by (heavy ion,x n) reactions, was studied with the particular aim of searching for high spin states of the (i13/2)^?3 configuration. The properties of levels in^{199, 197, 195}Pb are compared with the predictions of a three quasi-particle calculation, forJ=29/2?15/2, and with the corresponding results in the neighbouring even lead isotopes.     

Deuteron fragmentationd+p→p+p+n at 9 GeV/c

Gamma-ray energy correlations have been measured for several reactions leading to light-mass Hf isotopes with 160 ?A?166. The correlation spectra show ridge-valley structures up to high rotational frequencies from which a drop in J _c ⁽²⁾ is deduced at high frequencies. This drop suggests that a large portion of the angular momentum is generated by aligning particles. It may also be explained by the theoretically predicted triaxial states with large deformation.     

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.     

From the NN interaction to nuclear structure and reactions

We present a novel approach for the treatment of realistic nucleon-nucleon interactions in nuclear many-body systems. A unitary correlation operator is used to explicitly introduce short-range central and tensor correlations in many-body states. The correlated interaction is used as an effective interaction in nuclear structure calculations. Results for Lithium isotopes including proton and neutron distributions, radii as well as magnetic moments and quadrupole moments are shown. Molecular resonances in the ¹⁶O?¹⁶O system are given as a first application in reaction theory.     

Mass Measurements in Nuclear Reactions

The present status of mass measurements from reactions producing nuclei at the driplines, including those unstable to nucleon or cluster emission, is discussed. The results of recent heavy ion and π-meson induced experiments on the study of the superheavy hydrogen isotopes (⁴H, ⁵H, ⁶H), helium (⁹He, ¹⁰He), lithium (¹⁰Li, ¹¹Li) and beryllium (¹³Be) are given. The possibilities of mass measurements in radioactive ion beam experiments are also considered. This revised version was published online in July 2006 with corrections to the Cover Date.     

The “island of inversion" from a nuclear moments perspective and the g factor of 35Si

This paper reviews recent results from electromagnetic moment measurements on isotopes in the island of inversion around N=20. The obtained moments on neutron rich Na, Mg, Al and Si isotopes allow to draw conclusions on the amount of intruder components in their ground state wave function, demonstrating a gradual transition from the normal sd-shell region into the island of inversion, starting at N=18 for Na, N=19 for Mg and N=20 for Al isotopes. A measurement of the ground state g factor of ³⁵Si (N=21), using a polarized fragment beam at GANIL, is discussed in more detail. The magnetic moment μ(³⁵Si, I^π= 7/2^-) = (-)1.638(4) μ_N is consistent with a normal ground state structure, dominated by a νf_7/2 neutron.     

Determination of the static quadrupole moment of the first 2+ states of 122Te, 124Te,and 130Te by heavy-ion coulomb excitation

A Coulomb excitation experiment has been performed on the first 2⁺ states of ¹²²Te, ¹²⁴Te and ¹³⁰Te. The relative excitation probabilities of the first 2⁺ states were measured at backward and forward projectile scattering angles. Particle-γ coincidences were used to identify the inelastic events. The data were analyzed with the aid of the Winther-deBoer multiple Coulomb excitation program. Separate γ-ray angular distribution measurements were made as a function of target recoil velocity to determine the influence of the deorientation effect. The projectile and bombarding energy were chosen to minimize the effect on the experiment of higher state interference due to Coulomb excitation of the first 2⁺ state via the second 2⁺ state. For positive higher state interference the extracted quadrupole moments of the first 2⁺ states are Q₂₊ = ?0.43 ± 0.08 b, ?0.49 ± 0.08 b and ?0.08 ± 0.08 b for ¹²²Te, ¹²⁴Te and ¹³⁰Te respectively. These results and other measurements of Q_2⁺ for the doubly even Te isotopes are used to discuss the model dependent calculations of Q_2⁺.     

Single-neutron states at high spins in ytterbium nuclei: Evidence for the quenching of static neutron pair correlations

The decay schemes of ^167,168,169Yb are established to the largest angular momenta yet known in stably-deformed rare-earth nuclei using the ¹²⁴Sn(⁴⁸Ca,3–5n) reaction. The systematics of the resulting spectrum of single-neutron states in these and neighbouring Yb isotopes at large and small angular momenta are discussed with regard to that expected in the presence and absence of static neutron-pair correlations. This comparison, together with cranking-model and “gauge-space” analyses, provides evidence for the effective disappearance of static neutron-pair correlations for the odd-N isotopes at ?ω ? 0.38 MeV. A composite empirical spectrum of single-neutron states is constructed for the “unpaired” regime and is compared with cranking calculations.     

Investigating highly excited states of the 8Li isotope

Highly excited states of the ⁸Li isotope are sought in absorption reactions of π^? mesons stopped by ^10,11B isotopes. The ground and three excited states of the ⁸Li isotope are observed in inclusive measurements of reactions ¹⁰B(π^?, d)X and ¹¹B(π^?, t)X. The states with excitation energies E _x ≈ 8.7 and 10.1 MeV are observed for the first time in correlation measurements of reactions ¹⁰B(π^?, dt)X and ¹¹B(π^?, tt)X.     

Étude des isotopes du plomb de masse 200, 198, 196 et 194 formés par réaction (ions lourds, xn)

The low-lying excited states of ^{194, 196, 198, 200}Pb have been studied through the de-excitation γ-rays following the reactions Os(¹²C, 4n), W(¹⁶O, 4n) and Re(¹⁴N, 5n). Prompt and delayed spectra, γ-γ coincidences, γ-ray angular distributions and γ-ray time distributions have been obtained. Half-lives were measured for the 12⁺ level in the four isotopes, for the 9^? level in ^{194, 196, 200}Pb, for the ^7? level in ²⁰⁰Pb and for the ^5? level in ^{196, 198}Pb. The results of microscopic calculations, performed with either a Gaussian interaction or a surface delta interaction, are compared to the experimental level schemes and transition probabilities, and discussed.     

Simulation of photodisintegration of heavy nuclei

A comparative study of the results of the simulations of the photodisintegration of heavy nuclei in the energy range corresponding to the giant dipole resonance by the TALYS software package and by a combined model of is carried out. The cross sections of photoabsorption, photoneutron, and photoproton reactions and of the excitation of isomeric states for Hg and ²⁰⁸Pb isotopes are calculated. The results of the calculations are compared with the known experimental data.     

Penning trap mass measurements of rare isotopes produced by projectile fragmentation with LEBIT at NSCL

The Low-Energy Beam and Ion Trap facility LEBIT at the NSCL at MSU has demonstrated that rare isotopes produced by fast-beam fragmentation can be slowed down and prepared for precision experiments with low-energy beams. High-pressure gas-stopping was combined with advanced ion manipulation techniques to carry out these studies with a high-precision 9.4-Tesla Penning trap mass spectrometer. The spectrometer has been used for a series of high precision mass measurements of short-lived neutron- and proton-rich isotopes during the past year. This paper presents an overview of the LEBIT facility and summarizes the first mass measurement results. The mass measurements of ⁸¹Se, where ground and isomeric states have been resolved, and of ⁸⁰As will be discussed in detail.     

Hyperfine splitting constants in the optical transition \boldsymbol{{4{f}^{7}} {6{s}^{2}} \;{^{8}{\rm S}_{7/2}} \to {4{f}^{7}} {6{s}6{p}}\; {^{6}{\rm P}_{5/2}} \ {\rm of} \ {^{151-155}{\rm Eu}}} isotopes and hyperfine anomaly

Using the method of laser-induced fluorescence in an atomic beam we have measured the hyperfine splitting constants, A and B, of the ground and excited states of the optical transition 4f ⁷6s ^{2 8}S $_{1/2}\to 4f^{7}$ 6s6p ⁶P_5/2 (564.58 nm) for ^151???155Eu isotopes. For all isotopes, the magnetic dipole constants of the ⁶P_5/2 atomic level are determined to a precision better than 0.04%. The A and B constants for the ground state ⁸S_7/2 of the radioactive ^152,154,155Eu were obtained for the first time with a precision better than 0.5%. Our data along with previous ground state hyperfine structure measurements for the stable europium isotopes allow us to determine the hyperfine anomaly for mentioned Eu isotopes.     

Octupole vibrations in the even mercury and lead isotopes

Prominent groups are observed corresponding to excited states in the region of 2.6 MeV in the scattering of 24 and 27 MeV α-particles from ^{198, 200, 202, 204}Hg and ^{204, 206, 208}Pb. For each of the Pb isotopes the state concerned is identified with the known 3^? octupole vibration. Angular distribution measurements for scattering to the Pb and ²⁰⁴Hg states are in agreement with octupole-vibration coupled-channels predictions, and systematic trends suggest that the states observed in the isotopes ^{198, 200, 202}Hg can also be attributed to octupole vibrations.     

Hyperfine structure and nuclear magnetic moments of some neutron-deficient thallium isotopes

Using the atomic-beam magnetic resonance method, hyperfine structure (h.f.s.) measurements have been performed in the²P_1/2 electronic ground state of the neutron-deficient thallium isotopes^193–202Tl. In the doubly odd isotopes, the magnetic dipole hyperfine interaction constantsa were determined, while in the odd-A isotopes, direct measurements of the nuclearg-factors,g _I , were made. The electronicg-factor was measured in¹⁹⁸Tl. The magnetic dipole moments of the doubly odd isotopes have been evaluated by a direct comparison with known values in the stable isotope²⁰³Tl. The moments of the odd-A isotopes are in agreement with pervious measurements by optical spectroscopy. A discussion of the magnetic dipole moments in terms of different nuclear models is included. The moments of the 2^? nuclear ground states of the doubly odd isotopes may be interpreted as arising from a combination of the configurations 2^? (πs_1/2 vf_5/2) and 2^? (πs_1/2 vp_3/2).     

Properties of Zr isotopes near the neutron drip line and beyond it

The properties of neutron-rich Zr isotopes up to the neutron drip line and beyond it have been investigated on the basis of the Hartree-Fock method with the Skyrme forces (Ska, Sly4), taking into account the deformation. By the example of chains of Zr isotopes, good agreement is shown for the two-neutron separation energies and mean-square radii with the known results of Hartree-Fock-Bogolyubov calculations with the Sly4 forces. For the extremely neutron-rich Zr isotopes, states with very large deformation parameters (β ≈ 0.4?0.45) of neutron and proton density distributions can be realized. Beyond the neutron drip line with respect to emission of two neutrons, the existence of ^150,152Zr isotopes, which are stable with respect to one-neutron emission, is predicted.     

The photodisintegration of6Li and7Li

The photodisintegration of the stable Lithium isotopes has been investigated by spectroscopy of the emitted charged particles using the Giessen bremsstrahlung facility. Protons, deuterons, tritons,³He and alpha particles were detected and identified up to 20MeV particle energy. Angular distributions were measured using γ-ray energies up toE _γ =50 MeV. They are compared with theoretical predictions and with other experiments. A remarkable low (γ, t)-cross section was found for both isotopes in disagreement to previous measurements using virtual photons. Coincidence measurements between the emitted particles were performed in order to study the manybody-breakups of⁷Li.