Systematization of tensor mesons and the determination of the 2<Superscript>++</Superscript> glueball

It is shown that new data on the (J^PC=2⁺⁺) resonances in the mass range M～1700–2400 MeV support the linearity of the (n, M²) trajectories, where n is the radial quantum number of the quark-antiquark state. In this way, all the vacancies for the isoscalar tensor qq mesons in the range up to 2450 MeV are filled in. This allows one to fix the broad f₂ state with M=2000±30 MeV and Г=530±40 MeV as the lowest-tensor glueball.     

Dipole resonances in the electroexcitation of the <Superscript>24</Superscript>Mg nucleus

The wave functions and form factors of E1 excited states of the deformed nucleus ²⁴Mg are obtained within the particle-core coupling version of the shell model by using spectroscopic data on direct nucleon-pickup reactions. A comparison of the calculated E1-strength distributions with experimental cross sections shows the validity of the theoretical approach used, which is based on connections between direct and resonance nuclear reactions.     

Electron paramagnetic resonance of Cr<Superscript>3+</Superscript>-Li<Superscript>+</Superscript> centers in (Cr,Li): Mg<Subscript>2</Subscript>SiO<Subscript>4</Subscript> synthetic forsterite

Synthetic single crystals of chromium-and lithium-doped forsterite, namely, (Cr,Li): Mg₂SiO₄, are studied using electron paramagnetic resonance spectroscopy. It is revealed that, apart from the known centers Cr³⁺(M1) and Cr³⁺(M2) (with local symmetries C_i and C_s, respectively), these crystals involve two new types of centers with C₁ symmetry, namely, Cr³⁺(M1)′ and Cr³⁺(M2)′ centers. The standard parameters D and E in a zero magnetic field [zero-field splitting (ZFS) parameters expressed in GHz] and principal components of the g tensor are determined as follows: D=31.35, E=8.28, and g=(1.9797, 1.9801, 1.9759) for Cr³⁺(M1)′ centers and D=15.171, E=2.283, and g=(1.9747, 1.9769, 1.9710) for Cr³⁺(M2)′ centers. It is found that the lowsymmetric effect of misalignment of the principal axes of the ZFS and g tensors most clearly manifests itself (i.e., its magnitude reaches 19°) in the case of Cr³⁺(M2)′ centers. The structural models Cr³⁺(M1)-Li⁺(M2) and Cr³⁺(M2)-Li⁺(M1) are proposed for the Cr³⁺(M1)′ and Cr³⁺(M2)′ centers, respectively. The concentrations of both centers are determined. It is demonstrated that, upon the formation of Cr³⁺-Li⁺ ion pairs, the M1 position for chromium appears to be two times more preferable than the M2 position. Reasoning from the results obtained, the R₁ line (the ²E → ⁴A₂ transition) observed in the luminescence spectra of (Cr,Li): Mg₂SiO₄ crystals in the vicinity of 699.6 nm is assigned to the Cr³⁺(M1)′ center.     

Structure of the <Superscript>6</Superscript>He nucleus in the three-particle model

The properties of the ⁶He nucleus were investigated in a three-particle approximation (a alpha-particle cluster plus two neutrons) on the basis of the variational approach by using a Gaussian basis. For nn and nα interactions, potentials that make it possible to describe S-wave phase shifts for elastic scattering and, simultaneously, to reproduce faithfully the energy and the size of the ⁶He nucleus were proposed. Characteristic structural features of this nucleus that are manifested in the density distributions, elastic form factor, pair correlation functions, and momentum distributions of particles constituting the ⁶He nucleus in the three-particle model were revealed.     

Total strength of the magnetic dipole resonance in <Superscript>27</Superscript>Al

The γ decay of the resonance-like structure observed in the ²⁶Mg(pγ)²⁷ Al reaction in the energy range E _p = 0.8–3.0 MeV of accelerated protons has been investigated. The M1 resonance on the ground and excited states of ²⁷Al with E* = 844 and 1014 keV is identified. The total strength of the M1 resonance on the ground state of this nucleus is determined. The position and total strength of this resonance are explained taking into account pairing forces.     

Neutron single-particle structure of <Superscript>48</Superscript>Ca, <Superscript>50</Superscript>Ti, <Superscript>52</Superscript>Cr, <Superscript>54</Superscript>Fe,and <Superscript>56</Superscript>Ni nuclei

The change in the neutron single-particle structure of (1f?2p)-shell magic nuclei near the Fermi energy with an increase in the number of protons in the 1f _7/2 subshell from 0 for ⁴⁸Ca to 8 for ⁵⁶Ni has been investigated. Good agreement of the experimental and estimated values of the single-particle energies E _nlj of the bound states of neutrons in these nuclei with the results of calculations within the dispersive optical model is obtained.     

Theoretical study of photoionization of the isoelectronic sequence Rb<Superscript>+</Superscript>, Sr<Superscript>2+</Superscript>, and Y<Superscript>3+</Superscript>

The photoionization cross sections for the 4p shell of ions of the Kr isoelectronic sequence Rb⁺, Sr²⁺, and Y³⁺ are calculated. The configuration interaction theory and the perturbation theory are used to describe the many-electron effects. The relativistic effects are taken into account in the Pauli-Fock approximation. The calculated resonance structure of photoionization cross sections for the 4p shell in the region below the 4s threshold associated with the autoionization of the 4s-np singly excited states and the 4p4p-nln′l′ doubly excited states reproduces the results of recent measurements of total photoabsorption cross sections for the Rb⁺, Sr²⁺, and Y³⁺ ions. It is found that, as the nuclear charge in the isoelectronic sequence increases, the ratio between the direct and correlation parts of amplitudes of the 4s-(n/?)p transition changes and, as the consequence, the minimum of the photoionization cross section of the 4s shell shifts from the continuous spectrum to the region of states of discrete spectrum. This accounts for the strong changes in the shape of the 4s-np resonances in the photoionization cross sections for the 4p shell of Rb⁺, Sr²⁺, and Y³⁺, as well as the distinction between the shapes of the 4s-6p _1/2 mirror resonance in the partial 4p _1/2 and 4p _3/2 photoionization cross sections for the Y³⁺ ion which do not suppress each other in the total photoionization cross section, as is the case for similar resonances in Rb⁺ and Sr²⁺.     

Resonance Structure of the Charge-Exchange Strength Function and Neutrino-Capture Cross Sections for the Isotopes <Superscript>71</Superscript>Ga, <Superscript>98</Superscript>Mo,and <Superscript>127</Superscript>I

A resonance structure of the charge-exchange strength function S(E) and its effect on the neutrino-capture cross sections for the isotopes ⁷¹Ga, ⁹⁸Mo, and ¹²⁷I are studied within the self-consistent theory of finite Fermi systems. The calculation of the strength function S(E) takes into account Gamow–Teller, analog, and so-called lower lying pygmy resonances. The neutrino-capture cross sections σ(E) for the above three isotopes are calculated with allowance for the resonance structure of the strength function S(E), and the effect of each resonance on the energy dependence σ(E) is analyzed. It is found that all charge-exchange resonances in the strength function S(E) should be taken into account in calculating the neutrino-capture cross section σ(E) for the isotopes ⁷¹Ga, ⁹⁸Mo, and ¹²⁷I. The disregard of even highlying resonances leads to a substantial underestimation of the cross section σ(E), and this may affect the interpretation of respective experimental data.     

Band interaction in <Superscript>162</Superscript>Dy, <Superscript>168</Superscript>Er,and <Superscript>172</Superscript>Yb

Coriolis interaction between levels of two rotational bands in ¹⁷²Yb with K ^π = 2⁺ and 3⁺ and in ¹⁶⁸Er between levels with K ^π = 0^?, 1^?, and 2^? is studied. The values of the interaction parameters are obtained. The mutual influence of two bands in ¹⁶²Dy with ΔK = 2, K _i ^π = 0 ₂ ⁺ and 2 ₁ ⁺ due to Coriolis interaction is demonstrated.     

Interrelationship between the polarization moments of different parity upon optical pumping of atoms under the magnetic resonance conditions: I. Experiment on the <Superscript>133</Superscript>Cs and <Superscript>4</Superscript>He atoms

In an experiment with an optical pumping of ¹³³Cs atoms in the 6² S _1/2 ground state, the line shape of the D ^2f magnetic resonance signal for the transverse alignment component oscillating at a double frequency f of a radio-frequency (RF) magnetic field is found to strongly depend on the polarization of pumping radiation. On passage from a linearly polarized pumping light to a circularly polarized (CP) light with a sufficiently strong RF field the ordinary three-peak line with the highest central peak transforms into a two-peak line with a minimum at the center, so that the D ^2f signal line resembles the M ^f signal line of a transverse orientation oscillating at the RF field frequency f. This suggests that the orientation (the first-rank polarization moment (PM)) arising upon CP pumping affects the alignment (the second-rank PM); i.e., the PMs of Cs atoms with different parities of their ranks become coupled. No influence of the polarization of a pumping radiation on the line shape of the D ^2f signal is observed in a similar experiment with the ⁴He atoms in the 2³ S ₁ metastable state.     

Signature splitting in two quasiparticle rotational bands of <Superscript>180,182</Superscript>Ta

The signature splittings in K^π = 1 ⁺: 7 /2[404] _π?9 /2[624] _ν, K^π = 0^?: 9 /2[514] _π?9 /2[624] _ν bands of ¹⁸⁰Ta and K^π = 0^?: 7 /2[404] _π?7 /2[503] _ν, K^π = 1^?: 5 /2[402] _π?3 /2[512] _ν, K^π = 1⁺: 7 /2[404] _π?9 /2[624] _ν bands of ¹⁸²Ta are analysed within the framework of two-quasiparticle rotor model. The phase as well as magnitude of the experimentally observed signature splitting in K^π = 1⁺ band of ¹⁸⁰Ta, which could not be explained in earlier calculations, is successfully reproduced. The conflict regarding placement of a 12 ⁺ level in K^π = 1 ⁺: 7 /2 ⁺[404] _π?9 /2 ⁺[624] _ν ground-state rotational band of ¹⁸⁰Ta is resolved and tentative nature of K^π = 0^?: 7 /2[404] _π?7 /2[503] _ν, K^π = 1⁺: 7 /2[404] _π?9 /2[624] _ν bands observed in ¹⁸²Ta is confirmed. As a future prediction for experimentalists, these two-quasiparticle structures observed in ¹⁸⁰Ta and ¹⁸²Ta are extended to higher spins.     

Study of <Superscript>179</Superscript>Hf<Superscript><Emphasis Type="Italic">m</Emphasis>2</Superscript> excitation

Isomeric ratios of ¹⁷⁹Hf ^m2,g yields in the (γ, n) reaction and the cross section for the ¹⁷⁹Hf ^m2 population in the (α, p) reaction are measured for the first time at the end-point energies of 15.1 and 17.5 MeV for bremsstrahlung photons and 26 MeV for alpha particles. The results are σ = (1.1 ± 0.11) × 10^?27 cm² for the ¹⁷⁶Lu(α, p)¹⁷⁹Hf ^m2 reaction and Y _m2/Y _g = (6.1 ± 0.3) × 10^?6 and (3.7 ± 0.2) × 10^?6 for the ¹⁸⁰Hf(γ, n)¹⁷⁹Hf ^m22 reaction at Е _ep =15.1 and 17.5 MeV, respectively. The experimental data on the relative ¹⁷⁹Hf ^m2 yield indicate a single-humped shape of the excitation function for the ¹⁸⁰Hf(γ, n)¹⁷⁹Hf ^m2 reaction. Simulation is performed using the TALYS-1.4 and EMPIRE-3.2 codes.     

Hyperfine magnetic anomaly in isotopic pairs <Superscript>151, 152</Superscript>Eu and <Superscript>152, 153</Superscript>Eu

High-resolution laser spectroscopy measurements of optical hyperfine splitting on the ^{151, 152, 153}Eu isotopes were performed on the atomic transition 4f ⁷6s ^{2 8} S _7/2 → 4f ⁷6s6p ⁶ P _5/2 at λ ≈ 564.58 nm. Values of the nuclear magnetic dipole and electric quadrupole moments are obtained from the measured hyperfine splitting and the magnetic hyperfine anomalies in the isotope pairs ^{151, 152}Eu and ^{152, 153}Eu are deduced. The absolute values of the hyperfine anomaly in both cases are unusually large: 5 (1)%. The possible sources causing these anomalies are discussed.     

Energy distribution of the <Emphasis Type="Italic">E</Emphasis>1-transition strengths in the <Superscript>46</Superscript>Ti nucleus

The structure of levels of the ⁴⁶Ti nucleus is studied by means of the nonselective reaction ⁴⁵Sc(p, γ) at proton energies ranging between 1.2 and 3.1 MeV. Spin-parity assignments for ⁴⁶Ti states of excitation energies up to 5.5 MeV are obtained by using the method of averaged resonances. Radiative strength functions for E1 transitions populating these states are determined. The resulting data are compared with predictions of various models.     

Line shape of <Superscript>57</Superscript>Co sources exhibiting self absorption

The effect of selfabsorption in Mössbauer sources is studied in detail. Spectra were measured using an old ⁵⁷ C o/R h source of 74M B q activity with an original activity of ca. 3.7G B q and a 0.15G B q ⁵⁷ C o/α ? F e source magnetized by an in-plane magnetic field of 0.2 T. The ⁵⁷ C o/α ? F e source of a thickness of 25 μ was used both from the active and the inactive side giving cause to very different selfabsorption effects. The absorber was a single crystal of ferrous ammonium sulphate hexahydrate (FAS). Its absorption properties were taken over from a detailed study (Bull et al., Hyperfine Interact. 94(1–3), 1; Spiering et al. 2). FAS (space group P21/c) crystallizes as flat plates containing the (\(\overline {2}\)01) plane. The γ-direction was orthogonal to the crystal plate. The ⁵⁷ C o atoms of the ⁵⁷ C o/R h source were assumed to be homogeneously distributed over a 6μ thick Rh foil and to follow a one dimensional diffusion profile in the 25 μ Fe-foil. The diffusion length was fitted to 10 μ. The theory follows the Blume-Kistner equations for forward scattering (Blume and Kistner, Phys. Rev. 171, 417, 3) by integrating over the source sampled up to 128 layers.     

Projected Shell Model Description of Positive Parity Band of <Superscript>130</Superscript>Pr Nucleus

Theoretical investigation of positive parity yrast band of odd-odd ¹³⁰Pr nucleus is performed by applying the projected shell model. The present study is undertaken to investigate and verify the very recently observed side band in ¹³⁰Pr theoretically in terms of quasi-particle (qp) configuration. From the analysis of band diagram, the yrast as well as side band are found to arise from two-qp configuration πh _11/2???νh _11/2. The present calculations are viewed to have qualitatively reproduced the known experimental data for yrast states, transition energies, and B(M1) / B(E2) ratios of this nucleus. The recently observed positive parity side band is also reproduced by the present calculations. The energy states of the side band are predicted up to spin 25⁺, which is far above the known experimental spin of 18⁺ and this could serve as a motivational factor for future experiments. In addition, the reduced transition probability B(E2) for interband transitions has also been calculated for the first time in projected shell model, which would serve as an encouragement for other research groups in the future.     

Description of mixed symmetry states in <Superscript>96</Superscript>Ru using IBM-2

We have investigated the properties of low-lying states in ⁹⁶Ru within the framework of the neutron-proton interacting boson model (IBM-2), with special attention paid to the characteristics of the mixed symmetry states. By considering the relative energy of d proton boson to be different from that of neutron boson, the level energies and M1, E2 transition strengths have been calculated. The IBM-2 calculation is consistent with the experimental data of ⁹⁶Ru both quantitatively and qualitatively. Particularly, the strong M1 transition between the 4₂ ⁺ and 4₁ ⁺ states has been reproduced nicely. The calculated results show that the M1 transition strength of B(M1; 4₂ ⁺ → 4₁ ⁺) in ⁹⁶Ru can be described successfully by the IBM-2.     

Investigation of low-lying levels of the <Stack><Subscript>4</Subscript><Superscript>8</Superscript></Stack>Be nucleus in the multiquantum approximation of the orthogonal scheme

In the multiquantum approximation of the orthogonal scheme, specific calculations for the energies and radii of the ₄ ⁸ Be nucleus are performed with allowance for all states characterized by the λ=[44] Young diagram, the quantum numbers K_min and K_min+2 of the O(3(A?1)) group, and the quantum numbers E=K+2N (N≤9) of the U(3(A?1)) group. The convergence of the results with respect to the extension of the basis is studied, and the structure of relevant wave functions is revealed. The results of these calculations are compared with the results obtained in the analogous approximation of the unitary scheme.     

On the 0<Superscript>+</Superscript> state with the energy of 681.3 keV in <Superscript>160</Superscript>Dy

A possibility that the 0⁺ state with the energy of 681.3 keV exists in the ¹⁶⁰Dy nucleus is discussed. Calculations based on the interacting vector boson model show that in addition to the known 0⁺ states with the number of bosons n = 2, 5, 6, and 7 there should exist other states with the number of bosons n = 1, 3, 4, and 8 in ¹⁶⁰Dy. It is shown that the peak at the energy 681.3 keV, which we experimentally observed in the ¹⁶⁰Dy internal conversion electron spectrum, can be ascribed to the 0⁺ state with the number of bosons n = 1 or n = 8.