Few-valence-particle excitations around doubly magic 132Sn

Prompt γ-ray cascades in neutron-rich nuclei around doubly-magic ¹³²Sn have been studied using a ²⁴⁸Cm fission source. Yrast states located in the N = 82 isotones ¹³⁴Te and ¹³⁵I are interpreted as valence proton and neutron particle-hole core excitations with the help of shell model calculations employing empirical nucleon-nucleon interactions from both ¹³²Sn and ²⁰⁸Pb regions.     

Analysis of single-particle energies of doubly magic <Superscript>100,132</Superscript>Sn nuclei within the dispersive optical model

Extrapolation of the single-particle energies E _nlj of the bound states of neutrons and protons in the ^{112,116,118,120,124}Sn isotopes has been performed to estimate the values of E _nlj for unstable doubly magic ₅₀ ¹⁰⁰ Sn₅₀ and ₅₀ ¹³² Sn₈₂ nuclei. The estimates obtained are compared with the data derived from the analysis of the decay spectra of neighboring radioactive nuclei and with the results of the calculation within the dispersive optical model.     

Super-allowed α decay above doubly-magic <Superscript>100</Superscript>Sn and properties of <Superscript>104</Superscript>Te = <Superscript>100</Superscript>Sn ⊗ α

α-decay half-lives for ^{104, 105, 106}Te and ^{108, 109, 110}Xe close above the doubly-magic ¹⁰⁰Sn are calculated from systematic double-folding potentials. The derived α preformation factors are compared to results for ^{212, 213, 214}Po and ^{216, 217, 218}Rn above the doubly-magic ²⁰⁸Pb. α-decay energies of Q _α = 5.42±0.07MeV and 4.65±0.15MeV are predicted for ¹⁰⁴Te and ¹⁰⁸Xe; the corresponding half-lives are T _1/2 ≈ 5ns for ¹⁰⁴Te and of the order of 60μs for ¹⁰⁸Xe. Additionally, the properties of rotational bands in ¹⁰⁴Te are analyzed, and the first excited 2⁺ state in ¹⁰⁴Te is predicted at E _x = 650±40keV; it decays preferentially by γ emission with a reduced transition strength of 10 Weisskopf units to the ground state of ¹⁰⁴Te and with a minor branch by α emission to the ground state of ¹⁰⁰Sn.     

Binding and one-nucleon separation energies at <Superscript>132</Superscript>Sn

The paper presents the semiempirical method for the calculation of nuclear binding and one-nucleon separation energies of nuclei in the region of ¹³²Sn. The method is based on the multiparticle shell model, where the necessary input effective parameters are determined from the experimental data concerning nuclei in the close vicinity of the magical core. The text was submitted by the author in English.     

Shell-model structure of exotic nuclei beyond <Superscript>132</Superscript>Sn

We report on a study of exotic nuclei around doubly magic ¹³²Sn in terms of the shell model employing a realistic effective interaction derived from the CD-Bonn nucleon-nucleon potential. The short-range repulsion of the bare potential is renormalized by constructing a smooth low-momentum potential, V_low-k, that is used directly as input for the calculation of the effective interaction. In this paper we focus attention on the nuclei ¹³⁴Sn and ¹³⁵Sb which, with an N/Z ratio of 1.68 and 1.65, respectively, are at present the most exotic nuclei beyond ¹³²Sn for which information exists on excited states. Comparison shows that the calculated results for both nuclei are in very good agreement with the experimental data. We present our predictions of the hitherto unknown spectrum of ¹³⁶Sn.     

Nuclear masses and properties of nuclei in the vicinity of the remote magic nucleus <Superscript>100</Superscript>Sn

Results are presented that were obtained by calculating various properties of nuclei occurring in the vicinity of the doubly magic neutron-deficient nuclide ¹⁰⁰Sn, which are being intensively studied at present. The calculated features include the masses of 25 nuclei and the properties of excited states of the magic nuclide and of nuclei belonging to the magic core plus two quasiparticles type. The problems of effective quadrupole charges and of the renormalization of the weak axial constant in nuclei lying in the vicinity of ¹⁰⁰Sn are considered.     

Double-beta decay of <Superscript>100</Superscript>Mo to 0<Superscript>+</Superscript> excited states in <Superscript>100</Superscript>Ru

A brief review on the 2νββ decay of ¹⁰⁰Mo to the 0⁺ excited state in ¹⁰⁰Ru is performed. A weighted-average half-life value for the decay has been obtained, T_1/2 = (6.8 ± 1.2) × 10²⁰ yr. The corresponding average value for the nuclear matrix element was extracted, 0.095 ± 0.009.     

Shell model calculations with modified empirical Hamiltonian in the <Superscript>132</Superscript>Sn region

Using recent experimental information for the ¹³²Sn region, an empirical Hamiltonian is obtained by some modifications of a Hamiltonian (CW5082) originally derived from the ²⁰⁸Pb region. Shell model calculations with the new Hamiltonian show a remarkable improvement in the predictive power when compared with the available experimental results. It overcomes many limitations of the CW5082 Hamiltonian in this region, specially for isotones. The calculated level spectra and B(E2) values with the new Hamiltonian, also compare well with the available results calculated with the CD-Bonn and SKX Hamiltonians, reflecting consistency in the wave function structure at least in the low-lying regions. An interesting behaviour of effective charges is revealed in this region. It is shown that a drastic reduction of proton effective charge is necessary for obtaining B(E2) values for the N = 84 isotones. Neutron effective charge is found to be in the range (0.62-0.72)e. We predict the spectroscopic properties of ^135,136Sn not yet known experimentally. Further improvement of the modified Hamiltonian is also initiated.Received: 25 September 2003, Revised: 20 January 2004, Published online: 13 July 2004PACS: 21.60.Cs Shell model - 21.10.-k Properties of nuclei, nuclear energy levels - 23.20.-g Electromagnetic transitions - 27.60. + j      

Single-particle levels and spin-orbit splitting in the vicinity of the doubly magic nucleus <Superscript>48</Superscript>Ca

On the basis of a detailed analysis of available experimental data, the spectrum of single-particle states and the isotopic dependence of spin-orbit splitting are determined for nuclei in the vicinity of the doubly magic nuclide ⁴⁸Ca. The spectrum of excited states of the isobaric nucleus ⁴⁸Sc is calculated.     

Cluster structure of <Superscript>16</Superscript>O

A folding potential describing the -scattering on ¹⁶O over a broad energy range 25.8-146.0 MeV is constructed on the basis of -like cluster and unclustered-nucleon configurations of ¹⁶O. The resulting potential does not need any renormalization to fit the angular distribution of elastic cross-sections. The effects of the repulsive part of - and -nucleon interactions are investigated. The analysis suggests that both the - repulsive potential and the unclustered nucleonic configuration in the target are important to describe the scattering data over a broad range of incident energies. The root-mean-square radius for the ¹⁶O nucleus is deduced.Received: 5 December 2002, Published online: 9 October 2003PACS: 25.55.Ci Elastic and inelastic scattering - 24.10.Ht Optical and diffraction models - 21.60.Gx Cluster models     

Investigations of low- and high-spin states of <Superscript>132</Superscript>La

The fusion evaporation reaction ¹²²Sn(¹⁴N, 4n)¹³²La was used to populate the high-spin states of ¹³²La at the beam energy of 60 MeV. A new band consisting of mostly E2 transitions has been discovered. This band has the interesting links to the ground state 2^- and the isomeric state 6^-. A new transition of energy 351 keV connecting the low-spin states of the positive-parity band based on the πh _11/2 ⊗ νh _11/2 particle configuration, has been found. This has played a very important role in resolving the existing ambiguities and inconsistencies in the spin assignment of the band head. Received: 12 August 2002 / Accepted: 18 March 2003 / Published online: 7 May 2003     

Nuclear deformation and the two-neutrino double- β decay in <Superscript>124, 126</Superscript>Xe , <Superscript>128, 130</Superscript>Te , <Superscript>130, 132</Superscript>Ba and <Superscript>150</Superscript>Nd isotopes

The two-neutrino double-beta decay of ^{124, 126}Xe , ^{128, 130}Te , ^{130, 132}Ba and ¹⁵⁰Nd isotopes is studied in the Projected Hartree-Fock-Bogoliubov (PHFB) model. Theoretical 2ν β^-β^- half-lives of ^{128, 130}Te , and ¹⁵⁰Nd isotopes, and 2ν β⁺β⁺ , 2ν β⁺ EC and 2ν ECEC for ^{124, 126}Xe and ^{130, 132}Ba nuclei are presented. Calculated quadrupolar transition probabilities B(E2 : 0⁺ → 2⁺) , static quadrupole moments and g -factors in the parent and daughter nuclei reproduce the experimental information, validating the reliability of the model wave functions. The anticorrelation between nuclear deformation and the nuclear transition matrix element M _2ν is confirmed.     

Beta decay of <Superscript>115</Superscript>In to the first excited level of <Superscript>115</Superscript>Sn: Potential outcome for neutrino mass

Recent observation of β decay of ¹¹⁵In to the first excited level of ¹¹⁵Sn with an extremely low Q _β value (Q _β ≤ O(1) [keV]) could be used to set a limit on neutrino mass. To give a restriction potentially competitive with those extracted from experiments with ³H (≃2 eV) and ¹⁸⁷Re (≃15 eV), the atomic mass difference between ¹¹⁵In and ¹¹⁵Sn and energy of the first ¹¹⁵Sn level should be remeasured with higher accuracy (possibly of the order of ∼1 eV). The text was submitted by the authors in English.     

High-spin states and band structures in the doubly odd <Superscript>136</Superscript>La nucleus

High-spin states of ¹³⁶La have been investigated with the reaction ¹³⁰Te( ¹¹B, 5n) at a beam energy of 60 MeV. The level scheme with three collective bands has been updated with spin up to 20 . The observed h_11/2 h_11/2 band shows -instability with increasing spin according to the TRS calculations. The band crossing and the signature splitting and inversion have been discussed. Other two collective bands based on 12^-and 16⁺ levels were proposed as oblate deformation with -60^°. They most probably originate from four- and six-quasiparticle configurations, that is, h_11/2 g_7/2h_11/2² and g_7/2 g_7/2²d_5/2h_11/2² respectively.     

Sedimentological study of a lagoon through natural radioactivity and <Superscript>137</Superscript>Cs determinations

Profiles of artificial fallout (such as ¹³⁷Cs) and natural radioactivity radionuclides in sediment cores are useful tools to study sedimentological properties of different aquatic environments as well as to evaluate average sedimentation rates. In the Portil lagoon, a small natural reservoir located in Huelva province (southwest of Spain), and through the analysis of ²¹⁰Pb, ²²⁶Ra, ¹³⁷Cs, ²³⁸U and ²¹⁰Po vertical profiles in sediment cores, it is shown how the accumulative or transport character of the collection zones may be inferred. In the accumulation zone of the lagoon the influence of focusing effects has been analysed and an average sedimentation rate has been determined through ²¹⁰Pb in one sediment core. This ²¹⁰Pb-sedimentation rate is consistent with sediment dating based on the ¹³⁷Cs data.     

Isotopomer selective optimization of <Superscript>39</Superscript>K<Superscript>85</Superscript>Rb<Superscript>+</Superscript> and <Superscript>41</Superscript>K<Superscript>87</Superscript>Rb<Superscript>+</Superscript> using optimal control

We report on isotope selective three-photon ionization of two isotopomers of KRb by applying evolution strategies. The particularity of this experiment is based on the high resolution phase and amplitude modulation of the fs-laser pulses provided by a 2 × 640 pixel pulse shaper. The optimization in a closed feedback loop performed with spectrally broad pulses centered at 840 nm shows high enhancements of one isotopomer at the expense of the other isotopomer and vice versa. From the optimal laser field we aim to gain details about the selective ionization sequence and the wavepacket evolution on the involved vibrational states.     

Mass transfer during the prefission step in the 17.0-MeV/u <Superscript>132</Superscript>Xe+ <Superscript>238</Superscript>U interaction

The process of mass transfer is investigated occurring during the first of two steps of the 17.0-MeV/u ¹³²Xe + ²³⁸U heavy-ion reaction. Mass of the projectile-like nucleus after the first reaction step has been determined by the Fokker-Planck equation. Results have been compared with previously reported measurements.     

Search for hyperdeformed structures populated in the <Superscript>37</Superscript>Cl+<Superscript>120</Superscript>Sn reaction by using EUROBALL III

The ridge structure with ΔE_γ=±30 keV, observed in the past in coincidence with protons emitted in the reaction 187 MeV ³⁷Cl +¹²⁰Sn and attributed to an hyperdeformed nuclear shape in ¹⁵²Dy, has been studied in a new experiment performed with the EUROBALL III array. The ridge is now observed in coincidence with transitions in the yrast superdeformed band of ¹⁵²Dy but no discrete rotational bands have been identified. Received: 7 February 2000     

<Superscript>119</Superscript>Sn CEMS study of Sb doped SnO<Subscript>2</Subscript> film

Sb doped SnO₂ films prepared by DC sputtering and heating were characterized by ¹¹⁹Sn conversion electron Mössbauer spectrometry (CEMS). An asymmetric doublet was observed in the Mössbauer spectra of 1 %, 3 %, and 10 % Sb doped SnO₂ films. The peak ratios of doublets are considered to be due to the columnar crystal growth on the substrate. With the doping level of Sb, both the isomer shift (δ) and the quadrupole splitting (Δ) increased. After annealing, δ increased and Δ decreased for each sample. These results suggest the followings. The electron doping of the SnO₂ lattice by pentavalent Sb induces the increase of the electron density at the Sn^IV nucleus. The annealing process leads to more complete accommodation of the Sb dopant that results in more effective electron doping and therefore increasing isomer shift for tin. Simultaneously, the distortion of the lattice caused by Sb is relaxed and the quadrupole splitting decreases.