Nuclear spectroscopy of neutron-richA=145 nuclei

A study of theβ-decay of neutron-richA=145 fission products was undertaken by the use of the two recoil separators LOHENGRIN and JOSEF and the ISOL-type separator OSTIS. Theβ-decaying isotopes¹⁴⁵Ba,¹⁴⁵La and¹⁴⁵Ce were extensively studied. Level schemes for¹⁴⁵La,¹⁴⁵Ce and¹⁴⁵Pr were deduced fromγ and conversion electron spectra,γγ, X γ delayed andβγ coincidences. TheQ _β -values have been measured for the¹⁴⁵Ba,¹⁴⁵La and¹⁴⁵Ce decays.     

Nuclear charge asymmetry in the a = 3 nuclei

The nuclear charge asymmetry in the A = 3 system is determined by making a perturbative estimate of the direct electromagnetic (e.m.) contribution to the ³He-³H binding energy difference. All local e.m. contributions are estimated in an almost model-independent way using experimental charge form factors and the relation exploited previously by Fabre de la Ripelle and Friar only for the contribution of the static Coulomb interaction. Model-dependent wave functions are used for the contribution of the small non-local terms of the e.m. interaction and the proton-neutron mass difference. Only 81 ± 29 keV of the experimental binding-energy difference has to be attributed to nuclear charge asymmetry, an amount smaller than previous estimates. The nearly model-independent method is used to estimate the contribution of some two-body charge asymmetric potentials, both theoretical and phenomenological, to the binding-energy difference.     

Shell model yrast states in theN=79 nuclei141Sm and143Gd

In (α,5n) in-beam γ- and electron measurements we have established high-spin states in the 3-neutronhole nuclei¹⁴¹Sm and¹⁴³Gd. Observed energy levels below 4 MeV are interpreted in terms of shell model configurations where the odd h_11/2 neutron hole couples to the N=80 core excitations containing one h_11/2 proton particle or one h_11/2 neutron hole. Higher-lying yrast states are built on a 23/2? level at Rd 3.2 MeV probably involving the πh ₁ ^2/2 guh ₁₁ ^2/?1 configUTa-tion.     

The decay of 3.0 min143Eu and the levels of theN=81143Sm and141Nd nuclei

The decay of 3.0 min¹⁴³Eu has been investigated by means of a Ge(Li) detector. TheΒ ⁺ spectrum obtained with a Si(Li) spectrometer leads to aQ-value of 5100±50 keV. For the first time a decay scheme including levels situated at 107.5, 755.0, 1107.9, 1537.5 and 1912.8 keV has been established. The data are compared to those obtained for the neighbouringN=81¹⁴¹Nd nucleus. Besides, new experimental measurements indicate that the 1345.4 keV level in¹⁴¹Nd has not the odd-parity and would be 5/2⁺, 7/2⁺. Hence, the 7/2^? state is situated at 1967.4 keV. Those data are in reasonable agreement with intermediate coupling calculations.     

Nuclear ground-state spins of143Eu and157,158Tm

The nuclear ground-state spins of the rare-earth nuclides¹⁴³Eu,¹⁵⁷Tm and¹⁵⁸Tm have been measured by on-line ABMR techniques at the ISOLDE facility, CERN, giving the results I=5/2, 1/2 and 2, respectively.     

Anisotropy-correlated spectroscopy of quadrupolar nuclei

The two-dimensional anisotropy-correlated NMR (2DAC) spectra of half-integer quadrupolar nuclei may be recorded by using an exchange sequence in conjunction with magic angle spinning (MAS) during evolution and detection, and off-MAS during mixing. Application of this experiment to boron oxides is described, in addition to an analysis of the spin diffusion rates in such materials.     

One-nucleon spectroscopy of light nuclei

The capabilities and limitations of the conventional many-particle shell model and modern potential cluster models are discussed. New revaluated and more accurate calculations of one-nucleon spectroscopic characteristics of the light nuclei of 1p shell are presented. In many-particle shell model for nuclei with A = 7, 9, 11, 13, and 15 nucleon partial widths of highly excited states with the isotopic spin T = 3/2 were calculated both for “allowed” and “forbidden” transitions. One-nucleon spectroscopic factors were calculated in threebody multicluster models of ⁶Li{αnp}, ⁸Li{αtn}, and ⁹Be{ααn} nuclei. For isobar-analogue nuclei ⁷Li and ⁷Be, the spectroscopic proton S _p and neutron S _n factors for transitions to the ground and excited states of corresponding residue nuclei of the triplet ⁶Li-⁶He-⁶Be were calculated in the framework of binary potential αtand ατ models. Integral, differential and polarization characteristics of photonuclear processes ⁷Li(γ, n ₀)⁶Li, ⁶He(p, γ_{0 + 1})⁷Li, ⁷Li(γ, p ₀)⁶He, and ⁹Be(γ, p _{0 + 1})⁸Li were calculated in this approach.     

Detailed spectroscopy of superdeformed actinide nuclei

Progress in the experimental techniques used to investigate superdeformed fission isomers in the actinides allowed for detailed spectroscopic results of collective properties as well as for the identification of the rotational structure of multiphonon vibrational excitations. A novel approach could be established to determine the depth of the second potential well.     

Nuclear spectroscopy of90Y

The level structure of⁹⁰Y has been studied using the⁹¹Zr(t,α)⁹⁰Y and⁸⁹Y(n,γ)⁹⁰Y reactions. The proton pickup reaction was studied with 17 MeV tritons and a Q3D spectrometer. In the thermal⁸⁹Y(n, γ)⁹⁰Y reactionγ-rays from ≈100 to 6,857 keV were observed. In addition to previously known states and configurations, the ten states of theπ(p 3/2)^?1 v(d 5/2)¹ andπ(f 5/2)^?1 v(d 5/2)¹ configurations are assigned. Also many other new levels are identified from the (n, γ) data. The 0?state of theπ(f 5/2)^?1 v(d 5/2)¹ is assigned at 3,130keV. Finite-range shell model calculations suggest that the tensor force is necessary to reproduce the experimentally observed splittings.     

Rotor-encoded heteronuclear MQ MAS NMR spectroscopy of half-integer quadrupolar and spin I=1/2 nuclei

A new two-dimensional heteronuclear multiple-quantum magic-angle spinning (MQ MAS) experiment is presented which combines high resolution for the half-integer quadrupolar nucleus with information about the dipolar coupling between the quadrupolar nucleus and a spin I=1/2 nucleus. Homonuclear MQ coherence is initially created for the half-integer quadrupolar nucleus by a single pulse as in a standard MQ MAS experiment. REDOR recoupling of the heteronuclear dipolar coupling then allows the creation of a heteronuclear multiple-quantum coherence comprising multiple- and single-quantum coherence of the quadrupolar and spin I=1/2 nucleus, respectively, which evolves during t1. Provided that the t1 increment is not rotor synchronized, rotor-encoded spinning-sideband patterns are observed in the indirect dimension. Simulated spectra for an isolated IS spin pair show that these patterns depend on the recoupling time, the magnitude of the dipolar coupling, the quadrupolar parameters, as well as the relative orientation of the quadrupolar and dipolar principal axes systems. Spectra are presented for Na2HPO4, with the heteronuclear 23Na-1HMQ MAS experiments beginning with the excitation of 23Na (spin I=3/2) three-quantum coherence. Coherence counting experiments demonstrate that four- and two-quantum coherences evolve during t1. The heteronuclear spinning-sideband patterns observed for the three-spin H-Na-H system associated with the Na(2) site are analyzed. For an IS2 system, simulated spectra show that, considering the free parameters, the spinning-sideband patterns are particularly sensitive to only, first, the angle between the two IS internuclear vectors and, second, the two heteronuclear dipolar couplings. It is demonstrated that the proton localization around the Na(2) site according to the literature crystal structure of Na2HPO4 is erroneous. Instead, the experimental data is consistent with two alternative different structural arrangements, whereby either there is a deviation of 10 degrees from linearity for the case of two identical Na-H distances, or there is a linear arrangement, but the two Na-H distances are different. Furthermore, the question of the origin of spinning-sidebands in the (homonuclear) MQ MAS experiment is revisited. It is shown that the asymmetric experimental MQ sideband pattern observed for the low-C(Q) Na(2) site in Na(2)HPO4 can only be explained by considering the 23Na chemical shift anisotropy.     

Nuclear magnetic resonance of thermally oriented nuclei

The more recent developments in the spectroscopy of Nuclear Magnetic Resonance on Oriented Nuclei (NMRON) are reviewed; both theoretical and experimental advances are summarised with applications to On-Line and Off-Line determination of magnetic dipole and electric quadrupole hyperfine parameters. Some emphasis is provided on solid state considerations with indications of where likely enhancements in technique will lead in conventional hyperfine studies.     

Nuclear spectroscopy of molybdenum isotopes

The dependence of the properties of low-lying states of Mo isotopes on the mass number A = 83–117 is studied based on the collective and shell models of atomic nuclei. The variation of the nuclear shape with an increasing number of neutrons influences strongly the properties of excited states of Mo isotopes. Decay channels of isovector giant dipole resonance with emission of protons and neutrons are studied in the framework of the combined model. The basic mechanisms of the production of stable Mo isotopes in astrophysical nuclear reactions are described.     

Gamma spectroscopy of neutron-rich nuclei from the vicinity of the “island of inversion” atN=20

Neutron-richsdf shell nuclei produced by deep-inelastic processes in collision of 230 MeV³⁷Cl ions on a thick²⁰⁸Pb target have been studied via in-beam spectroscopic methods. Candidates for negative parity states in³²Si and³²Al have been identified. Yrast states with spins up to 13/2 have been located in the previously unknown³⁷P nucleus.     

Correlation NMR spectroscopy involving quadrupolar nuclei

We review the recent developments proposed for integer or half-integer quadrupolar nuclei, focussing on the methods to observe them under high-resolution and to analyze their through-space and through-bond connectivities.