Dipole excitations in the semi-magic nucleus 51V studied with the (γ,γ′) reaction

We report on a nuclear resonance fluorescence experiment on the semi-magic odd-mass fp-shell nucleus ⁵¹V. The detected dipole strength distribution is discussed on the basis of modern shell-model calculations employing a model space allowing for excitations of protons and neutrons from the 1f_7/2 to the (2p_1/2,2p_3/2,1f_5/2) shells. The calculations indicate that the main body of transitions is of magnetic dipole type, and they are capable of reproducing the observed distribution well. Possible electric dipole and quadrupole contributions are also discussed.     

Quasiparticle-phonon model calculations on doubly even Zn and Ge nuclei

The doubly even isotopes of Zn and Ge have been investigated in a model in which two quasiparticle excitations, constructed in a (0f _7/2), 1p _3/2, 0f _5/2, 1P _1/2, 0g _9/2 configuration space, are coupled with quadrupole vibrations of the core, viz.⁴⁰Ca or⁵⁶Ni. The 0f _7/2 orbit is excluded in case of a⁵⁶Ni core. The spectra, except for low-lying excited 0⁺ states, could be reproduced reasonably well. The calculatedE2 strengths and quadrupole moments are in fair agreement with experiment.     

Generalized Heisenberg theory of turbulence

The properties of the low-lying excited states of⁵³Mn have been investigated in the framework of the intermediate-coupling unified nuclear model. In the present calculations, it was assumed that three holes in the 1f _7/2 proton shell, which undergo excitations, are coupled to the quadrupole vibrations of the doubly even core. Energy levels and electromagnetic properties have been calculated. In most cases, the results are found to be in good agreement with the experimentally observed values for the low-lying excited states in⁵³Mn. The results are also compared with those obtained from other models.     

A shell-model study ofA=48–52 nuclei and magnetic strength distributions in50Ti

An extensive shell-model calculation has been performed on fivefp-shell nuclei in the mass regionA = 48–52. The model space, which includes 1p-1h excitations, reproduces the experimental spectra very well except for the 0 ₂ ⁺ state in⁵⁰Ti. It is demonstrated that the 0 ₂ ⁺ state can be reproduced by a model space which also includes 2p-2h excitations. Strong neutronp-h components in the wave functions of states in ₂₂ ⁵⁰ Ti₂₈ are found despite the closure of the neutron f_7/2 orbit. Magnetic transitions in⁵⁰Ti are discussed, and in contrast to the 1p-1h results a sufficiently large quenching ofB(M1) strengths in the 2p-2h model space is found. Effects of 2p-2h admixtures onM 5 transition strengths are discussed as well.     

Structure of odd Ge isotopes with 40 < N < 50

We have interpreted recentlymeasured experimental data of ⁷⁷Ge, and also for ^73,75,79,81Ge isotopes in terms of state-of-the-art shell-model calculations. Excitation energies, B(2) values, quadrupole moments and magnetic moments are compared with experimental data when available. The calculations have been performed with the recently derived interactions, namely with JUN45 and jj44b for f _5/2pg9/2 space. We have also performed calculation for fpg _9/2 valence space using an fpg effective interaction with ⁴⁸Ca core and imposing a truncation to study the importance of the proton excitations across the Z = 28 shell in this region. The predicted results of jj44b interaction are in good agreement with experimental data.     

A unified model calculation of states in odd-mass technetium isotopes

States in^{93, 95, 97, 99, 101}Tc are studied in a unified model calculation without any adjustable parameters except the excitation energy of the first 1/2^?state. The positive parity states are described as a mixture of (p _1/2)²(g _9/2) _J ³ and (p _1/2)⁰(g _9/2) _J ⁵ proton configurations coupled to a core undergoing quadrupole oscillations. For the negative parity states a proton quasi-particle in thep _1/2,p _3/2 andf _5/2 orbits is coupled to the vibrations. Calculated energies and electromagnetic moments agree quite well with available data.     

Investigation of hyperfine quadrupole interactions in UGe<Subscript>2</Subscript> and UAl<Subscript>2</Subscript> compounds on <Superscript>111</Superscript>Cd probe nuclei by the perturbed angular correlation method

The parameters of nuclear quadrupole hyperfine interaction in intermetallic UGe₂ and UAl₂ compounds have been measured in a temperature range of 100–300 K using the perturbed angular γγ correlation method on ¹¹¹Cd probe nuclei. The results obtained for UGe₂ indicate a pronounced anisotropic character in the distribution of f electrons in agreement with the calculation of the electronic structure of this compound. The hybridization degree between f electrons of U and p electrons of Al in UAl₂ is lower than the hybridization degree between f electrons of U and p electrons of Ge in UGe₂.     

Negative-parity states of75As and the interacting boson-fermion model

The result of an IBFM multilevel calculation with the 2p_3/2, 1f_5/2 and 2p_1/2 single particle orbits is reported for the negative parity states of the odd mass nucleus⁷⁵As. Comparisons are made with experimental data for energy spectra, transition probabilities, mixing ratios, electric quadrupole and magnetic dipole moments. Also, an IBM-1 calculation is presented for the low-lying states in the even-even⁷⁴Ge core nucleus.     

The hyperfine structure of they 8 p-multiplet of 4f 7(8 S) 6s 6p in EuI

The hyperfine splitting constants of the 4f ⁷ 6s 6p y ⁸ P _7/2 level of Eul were determined using the level crossing method. These values and those for the hyperfine splittings of the other 4f ⁷ 6s 6p levels are compared to theoretical values calculated with eigenfunctions of Smith and Collins. For the quadrupole coupling constants a better agreement between theory and experiment is obtained if different 〈r ^?3〉 _p -parameters are assumed for 4f(⁸ S) 6s 6p(³ P) and for 4f ⁷(⁸ S) 6s 6p(¹ P).     

Quasi-particle excitations around a pair of half-quantum vortices in p- wave superconductors

Triplet superconductors such as Sr₂RuO₄ and Na_xCoO₂⋅yH₂O are now found to be p-wave (p_x ± ip_y) or f-wave ((p_x ± ip_y) cos cp_z) superconductors. It was phenomenologically suggested that in these p-wave or f-wave superconductors, a pair of half-quantum vortices (HQVs) becomes stable. Using the Bogoliubov-de Gennes equation, previously we have analyzed quasi-particle excitations around an HQV at one end of a d-soliton for simplicity. In next study, we will investigate the stability of the pair of HQV’s, which are connected by the d-soliton. For this purpose, we have developed a new numerical method to solve the Bogoliubov-de Gennes equation for two vortices state, using Mathieu functions.     

Contribution of hexadecapole alignment to the polarization of quadrupole emission under laser excitation conditions

The linear polarization of quadrupole emission by the J=2-J ₀=0 transition under conditions of laser excitation in a gas medium is studied. Cases of excitation through dipole and quadrupole absorption of monochromatic laser radiation are considered. Taking into account the anisotropy of collisional relaxation, the contributions of polarization moments of the second and fourth ranks, i.e., those with usual and hexadecapole alignments, to the signal of linear polarization of quadrupole emission are calculated. The dependence of this signal on the laser frequency, the density of the gas medium, and the angles determining the orientation of the system of axes of observation of light polarization relative to a laser ray is studied. The numerical calculations of contributions of usual and hexadecapole alignment to the signal of linear polarization are made for the magnetic quadrupole transition J=2-J ₀=0 between the states 2p ⁵(² P ₁ ^2/0 )3p′[3/2]₂ and 2p ⁵(² P ₁ ^2/0 )3s 3s′[1/2]⁰ of neon atoms in the xenon atmosphere.     

TheN=83 nucleus149Dy from Gamow-Teller decay of its 11/2− and 1/2+ 149Ho parents

A high-sensitivityγ-spectroscopic study of the¹⁴⁹Hoπh _11/2 andπs _1/2 β-decays using mass separated sources has located dominant 0⁺ → 1⁺ GT decay strength associated with decay of pairedh _11/2 protons, leading to 3п-states in the¹⁴⁹Dy daughter nucleus. In theirγ-decay low-lying¹⁴⁹Dy levels characteristic of anN=83 nucleus are excited. They include theνf _7/2,νp _3/2,νh _9/2 andνp _1/2 single particle- and theνs ₁ ^2/?1 andνd ₃ ^2/?1 two-particle one-hole states, as well as the νf _7/2 × 3^? andνf _7/2 × 2⁺ particle-phonon multiplets. A synopsis is given of these excitations in theN=83 isotones from¹⁴⁹Nd to¹⁵³Yb. The¹⁴⁹Dy GT decay strength is discussed in terms of the¹⁴⁷Tb₈₂ and¹⁴⁸Dy₈₂ decays. The strength function results are also compared with independent¹⁴⁹Ho 11/2^? decay data from the literature based on totalγ-ray absorption measurements.     

Three-nucleon yrast states in145Sm

In-beamγ-ray and conversion electron measurements with (α, xn) reactions have established the¹⁴⁵Sm highspin states up toI ^π=25/2⁺ at 3.5 MeV excitation. A shell model analysis using empirical two- and one-body energies from neighbouring nuclei classifies the low-lying odd-parity levels as 3-quasiparticle states formed by the¹⁴⁴Sm two-proton-hole excitations and thef _7/2 valence neutron. The higher-lying positive-parity states involve particle-hole core excitations with one proton inh _11/2.     

Single-particle quadrupole electromagnetic transitions in p-shell and sd-shell nuclei

Electron scattering Coulomb form factors for the single-particle quadrupole transitions in p-shell and sd-shell nuclei have been studied. Core polarization effects are included through a microscopic theory that includes excitations from the core orbits up to higher orbits with 2ω excitations. The modified surface delta interaction is adopted as a residual interaction. The results are discussed for the ( 1p _1/2 ^-1↦1p _3/2 ^-1) proton transition in ¹⁵N, ( 1d _5/2↦2s _1/2) neutron transition in ¹⁷O and ( 1d _3/2 ^-1↦2s _1/2 ^-1) proton transition in ³⁹K. The inclusion of core polarization effects modifies the form factors markedly and describes the experimental data very well in both the absolute strength and the momentum transfer dependence. Received: 18 April 2002 / Accepted: 1 July 2002 / Published online: 6 March 2003 RID="a" ID="a"e-mail: baguniv@uruklink.net Communicated by A. Molinari     

Effects of configuration mixing on predominantlyf 7 2/n states inA=52–55 nuclei

Extensive shell-model calculations are performed onf _7/2 nuclei withA=52–55. The model space includes the excitation of onef _7/2 nucleon to thep _3/2,f _5/2 orp _1/2 orbit. Spectra, electromagnetic properties (M1,E2,E4) andβ-decay are studied. It is found that almost all observables calculated in the enlarged space are in much better agreement with experiment than those of the simplef ₇ ^2/n space.     

Spectroscopic investigations and configuration-interaction-assisted crystal field analysis of Pr in YPO4 single crystal

An optical study of a Y_0.99Pr_0.01PO₄ single crystal is presented. Measurements of optical absorption, excitation, and emission by selective excitation into ¹D₂, ³P₀ and ³P₁, at different temperatures between 20 and 295 K, are described. A detailed account of the line assignments is given for absorption in the 4300-23 000 cm⁻¹ spectral range, and for emission in the 6400-23 000 cm⁻¹ range. The lifetimes of the emitting levels are determined. Vibronic sidebands accompanying absorption, emission and excitation spectra are reported. The decay processes of the ³P₁, ³P₀ and ¹D₂ levels are discussed. The aim of this study is a test of the configuration-interaction-assisted crystal field analysis as well as the accurate experimental determination of the energy level scheme. It was reported previously that the introduction of configuration interaction between the ground 4f² configuration with the excited 4f6p configuration always resulted in a decrease (≈50-60%) in the standard deviations between the observed and calculated energy levels. In the present work the 4f5d configuration is included as well. The crystal field is analysed in the theoretical D_2d site symmetry with and without configuration interaction. The results with 4f², 4f²+4f5d, 4f²+4f6p and 4f²+4f5d+4f6p are given. The calculation on the basis of the 315 (4f²+4f5d+4f6p) levels gives the best overall standard deviation lowering it by 75% with regard to the calculation on the 91 4f² levels only.     

Effect of quadrupole and octopole vibrations of206Pb on the 1j 15/2 neutron particle state of207Pb

The quadrupole as well as the octopole vibrational states of²⁰⁶Pb are coupled to the 2g _9/2, 1i _11/2 and 1j _15/2 neutron states to explain the fragmentation of 1j _15/2 state in²⁰⁷Pb as observed in the²⁰⁶Pb(d,p) reaction. The structures of weak fragmented 1j _15/2 states are deduced through the particle-core coupling scheme.     

Hyperfine structure measurements in metastable states of165Ho

The hyperfine structure constants and the electronic g _J factor of the state 4f ¹¹ 6s ^{2 4} I _11/2 belonging to the holmium ground multiplet have been measured using the atomic beam magnetic resonance technique combined with a state-selective laser-induced detection of the resonant atoms. By the same method the g _J factor of the level 4f ¹¹6s ²⁴ I _9/2 was determined, while the hyperfine structures of this metastable state and of two high-lying even parity states have been investigated by high resolution laser spectroscopy. The results for the experimentalA andB factors of all four members of the ground multiplet allow a least-squares evaluation of the three magnetic dipole and the three electric quadrupole effective radial parameters for the configuration 4f ¹¹ 6s ² of holmium, yielding an accurate value for the spectroscopic nuclear electric quadrupole moment:Q _hfs(¹⁶⁵Ho)=2.716(9)b (uncorrected for quadrupole shielding). From a comparison to the quadrupole moments measured in mesic holmium atoms the shielding factor could be estimated.     

Exploring effective interactions through transition charge density study of70,72,74,76Ge nuclei

Transition charge densities (TCD) for 0⁺ → 2 ₁ ⁺ excitation have been calculated for^70,72,74,76Ge nuclei within microscopic variational framework employing 2p _3/2, 1f _5/2, 2p _1/2 and 1g _9/2 valence space. The calculated TCDs for different monopole variants of Kuo interaction are compared with available experimental results. Other systematics like reduced transition probabilitiesB(E2) and static quadrupole momentsQ(2) are also presented. It is observed that the transition density study acts as a sensitive probe for discriminating the response of different parts of effective interactions.     

Calculations of the energy spectra of Zn,Ga, and Ge isotopes by the shell model

The effective Hamiltonian which was determined empirically by Koops and Glaudemans is tested in shell model calculations for the^65–68Zn,^67–69Ga, and^68–70Ge nuclei in the full (1p _3/2,0f _5/2,1p _1/2) ⁿ space. The resulting energy spectra are compared with the experimental spectra and results of previous calculations. The overall agreement with experiment is as satisfactory for these nuclei as for the Ni and Cu isotopes, by which the Hamiltonian was determined. It is noticed that the spectra of⁶⁷Zn and^67,69Ga calculated in this work are similar to those provided by the Alaga model.