Groundstate proton radioactivity of nuclei in the tin region

Proton radioactivities with decay energies of (0.98±0.08) MeV and (0.83±0.08) MeV were produced by the fusion reactions⁵⁸Ni+⁵⁸Ni→¹¹⁶Ba ? and⁵⁸Ni+⁵⁴Fe→¹¹²Xe ?, and their halflives were measured to be (33±7) μs and (109±17) μs, respectively. The intensities of the lines correspond to production cross sections of about 30 μb and 40 μb. The two activities are assigned to the direct proton decay of¹¹³Cs and¹⁰⁹I. The measured halflives are compared with values calculated ford _5/2 andg _7/2 groundstates of¹⁰⁹I and¹¹³Cs and spectroscopic factors are deduced for the decays. An extensive search for the proton decay of¹⁰⁵Sb, produced in the reaction⁵⁰Cr(⁵⁸Ni,p2 n)¹⁰⁵Sb, had a negative result, excluding decay energies between 0.5 MeV and 1.5 MeV for halflives between 10 ns and 5 s.     

Mass measurements far from stability around theN=Z line (100Sn,100In,100Cd)

Secondary ions of¹⁰⁰Ag,¹⁰⁰Cd,¹⁰⁰In and¹⁰⁰Sn were produced via the fusion-evaporation reaction⁵⁰Cr+⁵⁸Ni at an energy of 5.1 MeV/nucleon. TheA=100 secondary ions were accelerated in the second cyclotron of GANIL, which was used as a high-resolution mass spectrometer. The masses of the three latter isobars were measured with respect to the abundantly produced¹⁰⁰Ag. The known mass of¹⁰⁰Cd was very well reproduced and the masses of¹⁰⁰In and¹⁰⁰Sn were determined for the first time with precisions of 3×10^?6 and 10^?5, respectively.     

Decay properties of the new proton-rich nucleus104Sn: Mass determinations beyond the proton drip line

The new proton-rich nucleus¹⁰⁴Sn was produced in a⁵⁰Cr(⁵⁸Ni, 2p2n)¹⁰⁴Sn reaction. Its half-life was measured to be 21±1s. From a newly established partial decay scheme, aQ _EC value of 4,000 _?300 ⁺⁶⁵⁰ keV was estimated. The resulting mass excess value for¹⁰⁴Sn, combined with decay energies for α and proton emission, leads to mass excess values for the nuclei¹⁰⁸Te,¹⁰⁹I,¹¹²Xe, and¹¹³Cs. These mass values are compared to predictions of mass formulae.     

Investigations of very neutron-deficient isotopes below100Sn in40Ca-induced reactions

Very neutron-deficient isotopes of rhodium, palladium, silver, cadmium and indium in theN=50 region were studied at the GSI on-line mass separator following bombardment of^{58, 60, 62}Ni and^{63, 65}Cu targets with 4.0 MeV/u ions of⁴⁰Ca. The known properties of the β-delayed proton precursor^95m Pd were confirmed, but a search for direct proton decay of^95m Ag was not successful. Beta-delayed proton activities observed at mass-numbers 94, 96, 97 and 100 were assigned to the precursors⁹⁴Rh(66±14 s),⁹⁶Ag(5.1±0.4s),⁹⁷Cd(3 _?2 ⁺⁴ s) and¹⁰⁰In. In addition,⁹⁴Pd(9.0±0.5 s) was identified from β-γ-X studies. Individual decay schemes of^95m96Pd and^{96, 98}Ag are reported.     

Beta decay of 101Sn

The β decay of the very neutron-deficient isotope ¹⁰¹Sn was studied at the GSI on-line mass separator using silicon detectors for recording charged particles and germanium detectors for γ-ray spectroscopy. Based on the β-delayed proton data the production cross-section of ¹⁰¹Sn in the ⁵⁰Cr + ⁵⁸Ni fusion-evaporation reaction was determined to be about 60nb. The half-life of ¹⁰¹Sn was measured to be 1.9(3)s. For the first time β-delayed γ-rays of ¹⁰¹Sn were tentatively identified, yielding weak evidence for a cascade of 352 and 1065keV transitions in ¹⁰¹In. The results for the ¹⁰¹Sn decay as well as those from previous work on the ¹⁰³Sn decay are discussed by comparing them to predictions obtained from shell model calculations employing a new interaction in the ⁸⁸Sr to ¹³²Sn model space.     

Constraint Molecular Dynamics and results on isotopic distributions produced in heavy ion collision — The Sn + Ni systems

The Constraint Molecular Dynamics approach is illustrated together with calculation on different heavy ion collisions. In particular the charge-mass distribution produced in the collision ¹²⁴Sn + ⁶⁴Ni and ¹¹²Sn + ⁵⁸Ni at 35 MeV/nucleon is discussed. By comparing the Y = (N ? Z)/A distributions for fragments produced in central collisions it results that this observable can be sensitive to the dynamic effects induced on the two systems by the different charge/mass ratio.     

In-beam study of102Sn

Excited states in¹⁰²Sn have been identified for the first time, in an in-beamγ-ray spectroscopic experiment. Twoγ-ray transitions with energies 1472 and 497 keV following the decay of the seniority 6⁺ isomer with t_1/2=1.0(5)μs were unambiguously assigned to¹⁰²Sn. Due to the very low cross section of about 2µb for producing¹⁰²Sn in the reaction⁵⁰Cr(⁵⁸Ni,1α2n), a highly selective detector setup utilizing NORDBALL ancillary detectors and a recoil catcher device was used. Highγ-ray detection efficiency was achieved with two EUROBALL Ge cluster detectors.     

Ratios of gI-factors and hyperfine structure anomalies of115Sn,117Sn and119Sn

The ratios of the g_I-factors of¹¹⁵Sn,¹¹⁷Sn and¹¹⁹Sn have been measured by the NMR method in different solutions which have large chemical shifts. No primary isotopic effect on the magnetic shielding was found within the error of 7·10^?7. Therefore the ratios have been used for the calculation of the hyperfine structure anomalies in the³P₁,³P₂ and¹D₂ atomic states of the given tin isotopes.     

The decay of 0.57 s114Cs

Fusion reactions between⁵⁸Ni projectiles and⁵⁸Ni target nuclei were used to produce¹¹⁴Cs activity, which was studied by on-line mass separation and decay spectroscopy. The obtained half-life of 0.57±0.02 s and the probability ratio of 44±3 between betadelayed proton and beta-delayed alpha emission represent data with improved precision. The absolute branching ratios for both particle decay modes were determined to be (7 ±2)×10^?2 and (1.6±0.6)×10^?3, respectively. These branching ratios and the shapes of particle spectra are discussed with reference to the statistical model calculations. Groundstate alpha decay of¹¹⁴Cs was observed with an alpha energy of 3,226±30 keV and a branching ratio of (1.8±0.6)×10^?4. An upper limit of the branching ratio for a possible ground-state proton decay was set at 5×10^?4. Fromγ-ray singles andγ-γ coincidence measurements, excited states in¹¹⁴Xe are proposed.     

In-beam study of 102Sn

Excited states in ¹⁰²Sn have been identified for the first time, in an in-beam γ-ray spectroscopic experiment. Two γ-ray transitions with energies 1472 and 497 keV following the decay of the seniority 6⁺ isomer with t_1/2 = 1.0(5) μs were unambiguously assigned to ¹⁰²Sn. Due to the very low cross section of about 2 μb for producing ¹⁰²Sn in the reaction ⁵⁰Cr(⁵⁸Ni,1α2n), a highly selective detector setup utilizing NORDBALL ancillary detectors and a recoil catcher device was used. High γ-ray detection efficiency was achieved with two EUROBALL Ge cluster detectors.     

Angular momentum dissipation in16O +58Ni collisions investigated by observation of light particles andγ rays

A systematic study of angular momentum dissipation in deep-inelastic heavy ion collisions is carried out by combining two experimental methods: the angular correlation ofα particles and protons in coincidence with deeply inelastic light fragments; and the first two moments of theγ-ray multiplicity. The unified analysis of these data, using a quantum mechanical treatment of the particle anisotropies and statistical decay calculations, yields most probable fragment spinsI ₀=10.8±1.1? and 13.4±1.1? for⁵⁸Ni and⁶²Zn, respectively, close to the sticking limit. For the width of the vector spin distribution assumed in our analysis to be equal in all three directions we obtainσ=3.9±1.3 ? and 2.9±1.8? for⁵⁸Ni and⁶²Zn, respectively. These values correspond to most probable alignment parameters 〈P _zz〉=0.66±0.19 and 0.82±0.17 for⁵⁸Ni and⁶²Zn, respectively. As only very few partial waves of this light system undergo deep-inelastic scattering,σ directly relates to spin fluctuations, and is compared to asymptotic values from transport theories.     

Q EC value and Gamow-Teller strength of the102CdEC/gb+ decay

Within the framework of a systematic study of 0⁺→1⁺ Β-transitions in the¹⁰⁰Sn region, the decay of the neutrondeficient isotope¹⁰²Cd was investigated. This isotope was produced in¹⁶O+⁹²Mo and⁵⁸Ni+⁵⁰Cr heavy-ion reactions and in proton-induced spallation of^natSn, and mass-separated samples were prepared by means of the GSI and the ISOLDE on-line mass separators, respectively. Observations of X-rays,γ-rays, and conversion-electrons studies have led to an improved¹⁰²Cd→¹⁰²Ag decay scheme which includes six 0⁺→1⁺ Gamow-Teller transitions. The half-life of¹⁰²Cd was redetermined with higher accuracy to be 345±8 s. Using a Si(Li)-BGO-Ge spectrometer, theΒ ⁺ endpoint energy of the main decay component was measured, yielding aQ _EC value of 2587±8 keV. This very small uncertainty ofQ _EC, combined with the improved knowledge of half-life and decay scheme, allows an accurate determination of the observed Gamow-Teller decay strengthB _Σ (GT)=1.513±0.055 for¹⁰²Cd. This result is discussed in comparison with predictions from model calculations.     

Specific heat of the superfluid neutron matter in neutron star crusts

By means of X-γ andγ-γ coincidence measurements of the³⁵Cl+⁵⁸Ni reaction products, 38γ lines have been identified to be in coincidence with KX(Tc)-rays and assigned to the decay of⁹⁰Ru. Its half-life of 11±3 s has been deduced from the 154.6 keVγ-decay. The result supports our previous identification of⁹⁰Ru produced in the same reactions.     

Measurements of fusion reactions induced by radioactive 132Sn on 64Ni

Evaporation residue and fission cross sections of radioactive ¹³²Sn on ⁶⁴Ni were measured. Statistical model calculations using parameters simultaneously fitting stable Sn+⁶⁴Ni data reproduce the ¹³²Sn induced reaction very well. A large sub-barrier fusion enhancement was observed. The enhancement can be accounted for by coupled-channels calculations including inelastic excitation of the projectile and target, and neutron transfer.     

Measurement of partial radiation widths of high energy transitions from keV capture resonances in56Fe and58,60Ni

High energyγ-ray transitions to low-lying states following neutron capture in⁵⁶Fe and^58,60Ni have been investigated for individual resonances in the neutron energy range 7–70keV using a 50cc Ge(Li)-detector. Partial radiation widths fors- and 1>0 wave resonances were determined. For the 1>0 wave resonance in⁵⁸Ni at 47.8 keV a spin of 3/2 was derived. Theγ-ray strength forM1 transitions was found to be (21±17)×10^?9 and (16±7)×10^?9MeV^?3 for⁵⁶Fe and⁵⁸Ni, respectively. The partial radiation widths of the studieds-wave resonances were compared with valence model calculations.     

E2 polarization charge in Sn

The nucleus ¹⁰²Sn, which is the lightest Sn isotope with known excited states, was investigated with the ⁵⁰Cr(⁵⁸Ni,α2n) reaction using delayed in-beam γ-ray and conversion-electron spectroscopy. The experimental setup was designed to study the decay of μs-long isomeric states by placing γ-ray and electron detectors behind the focal plane of the Fragment Mass Analyzer at the Argonne National Laboratory. A 44 keV conversion-electron line corresponding to the (6⁺)→(4⁺) transition in ¹⁰²Sn was identified and a half-life of 0.62^+0.43_−0.19 μs was measured for the (6⁺) state. From the available experimental information neutron effective charges from 1.6 to 2.3 e were deduced, based on the comparison with different shell-model calculations.     

Magneto-crystalline properties of BaFe12−2x M x Sn x O19 (M = Sn, Ni, Zn) ferrite powders

BaFe_12?2x M _x Sn _x O₁₉ compounds, where M?=?Sn²⁺, Ni²⁺ or Zn²⁺ ions, were synthesized by mechanical milling and partially by citrate precursor methods. Analysis of magneto-crystalline structure has been carried out by Mössbauer spectroscopy. The Sn⁴⁺ ions replace Fe³⁺ ions on 2b and slightly on 2a?+?4f₁ sites, Zn²⁺ ions strongly prefer 4f₁ sites, Sn²⁺ ions prefer 4f₁ sites too and Ni²⁺ ions occupy 4f₂ and 12k or 2a sites. The magnetic properties were evaluated by the vibrating sample magnetometry and the thermomagnetic analysis. A large variation of the intrinsic coercivity H _c (330 to 78 kA/m) and of temperature coefficient of coercivity of ΔH _c /Δ? (0.39 to 0.22 kA/m°C) were achieved as a function of the (Zn–Sn) and (Sn–Sn) substitutions, respectively. The Curie temperature T _c decreased with the (Ni–Sn) substitution from 447 to 399°C.     

In-beam spectroscopy of104Sn

The very neutron deficient nucleus 104Sn has been identified in in-beam spectroscopy using the reaction⁵⁰Cr(⁵⁸Ni, 2p2n) and neutron and charged particle multiplicity filter detectors. Excited states up to I ≈ 10 and E_x=4 MeV were observed and the level scheme is discussed in the frame work of the spherical shell model.     

In-beamγ-ray spectroscopy of the odd-odd nucleus144Tb

The level scheme of theN=79 nucleus¹⁴⁴Tb was investigated via in beamγ-ray spectroscopy using the¹¹²Sn (³⁵Cl,n2p),¹¹⁶Sn(³²S, 3np) and⁸⁹Y(⁵⁸Ni, 2np) reactions. States up toI～20 andE _x～5 MeV were established above the 6^? β ⁺ decaying isomer. Two new isomers with half-life of 0.67(6) µs and 2.8(3) µs were identified. The level scheme of¹⁴⁴Tb is interpreted in the framework of the spherical shell model with a few valence nucleons outside the¹⁴⁶Gd core.     

99Ru,61Ni,57Fe,and119Sn Mössbauer studies of Heusler alloys containing ruthenium

⁹⁹Ru,⁶¹Ni,⁵⁷Fe and¹¹⁹Sn Mössbauer spectroscopic studies were made on ternary intermetallic compounds containing ruthenium, Ru_xY_3?xZ (Y=Fe, Ni; Z=Si, Sn). In the system of Ru_xFe_3?xSi, two different hyperfine magnetic fields were observed at the⁹⁹Ru nuclei (H _hf[Ru]) in the range ofx≤1.0 and the magnitude of eachH _hf[Ru] was found to decrease with an increase in the ruthenium concentrationx. Both the⁹⁹Ru and¹¹⁹Sn Mössbauer spectra of Ru₂FeSn could be analyzed with two sets of magnetically split lines. The⁶¹Ni Mössbauer spectra of Ru₂NiSn were obtained at 5 and 77 K.