Results on two-, three-, and four-body events from the100Mo+100Mo and120Sn+120Sn collisions aroundE/A=20 MeV

Events with 2, 3 and 4 heavy-fragments (A≧20) have been detected in the reactions¹⁰⁰Mo+¹⁰⁰Mo atE/A =18.7, 23.7 MeV and¹²⁰Sn+¹²⁰Sn atE/A=18.4 MeV. The experiments were performed with an array of 12 detectors which together covered a large fraction of the forward hemisphere and allowed a high detection efficiency for these events. Masses and energies of all fragments have been reconstructed by means of an improved version of the kinematic coincidence method. The probabilitiesP ₃ andP ₄ of producing 3- and 4-body events were found to depend mainly on the dissipated energy rather than on the bombarding energy, thus indicating that their origin lies more in the decay properties of the excited fragments than in the dynamics of the interaction. Emission of light particles from the composite system is shown to become more relevant with increasing bombarding energy and may explain the drop of theP ₃ andP ₄ curves at high energy losses. Small deviations of theP ₃ andP ₄ curves at 23.7A · MeV from those at lower bombarding energies were used to estimate the amount of a possible pre-equilibrium light particle emission as a function of impact parameter.     

The deformation of the ground and excited states in the Ag and Sn nuclei

The microscopic calculation of the potential energies in the ground and excited states of Ag and Sn nuclei has been performed. The single particle Nilsson potential and the shell correction Strutinski method have been used. The weak sensitivness to nonaxial deformation has been found for even neighbours of these nuclei. The small tendency towards prolate deformation of the ground and excited one-quasiparticle states originating from theg _9/2 proton subshell in^101–105Ag odd isotopes has been noticed. The behaviour with quadrupole e and hexadecapole ε₄ deformation of the ground and two-quasiparticle excited 0⁺ states originating from thed _5/2,g _9/2 andg _7/2 proton subshells andh _11/2 neutron subshell in^112–118Sn has been investigated. The small quadrupole deformation of the excited 0⁺ states has been found what is in agreement with the experimental data concerning the rotational bands build on the first excited 0⁺ states in Sn isotopes.     

Transition probabilities and energy levels in heavy odd-mass isotopes of Sn (A=119–125)

The de-excitation of levels in^119–125Sn populated in the decay of In isotopes has been studied using on-line isotope separators. Level half-lives have been measured in^119–123Sn. a near cancellation of the matrix element for B(E2; g_7/2→ d_3/2) is observed to occur in¹²¹Sn and is probably due to pairing effects. Very low lying 9/2^? levels have been observed in^121–125Sn and are suggested in^{127, 129}Sn. These levels have been interpreted as three quasi-particle states based on the unique parity h_11/2 level. A possible mixing of theg _7/2 level with a close lying 7/2⁺ three quasi-particle state in¹²³Sn is discussed. Radioactivity.^119–125In from²³⁵U(n, f) and²³⁸U(α, f), isotope separated sources; measuredE _γ ,I _γ , E_ce, I_ce,γγ-coin,Βγ-delay, deduced multipolarities.^119–123Sn deduced levels,I, π, B(λ). Ge(Li), Si(Li), NaI(Tl) and plastic detectors, Ge(Li)-Ge(Li) coin, plastic detector — NaI(Tl) delay.     

The new beta-delayed proton precursors103Sn and105Sn

Using⁵⁸Ni+⁵⁰Cr and⁵⁸Ni+⁵⁴Fe reactions and on-line mass separation, the new isotopes¹⁰³Sn and¹⁰⁵Sn with half-lives of 7±3 s and 31±6 s, respectively, were identified via their beta-delayed proton decays. The relative yields and the possibility of reaching¹⁰¹Sn are discussed.     

57Fe,119Sn and151Eu Mössbauer study of EuBa2(Cu1−x−y 119Sn x 57Fe y )3O7−δ superconductor

¹⁵¹Eu,¹¹⁹Sn and⁵⁷Fe Mössbauer spectroscopy was used to study a EuBa₂(Cu_1?x?y Sn _x Fe _v )₃O_7?δ superconductor in which sites were replaced by all three Mössbauer isotopes in the same sample in order to get information about the site preferences and structural changes. We have found changes in the Mössbauer parameters of the⁵⁷Fe,¹¹⁹Sn and¹⁵¹Eu spectra compared to those recorded in the separately substituted EuBa₂Cu₃O_7?δ, EuBa₂(Cu_1?x Sn _x )₃O_7?δ, YBaCu_3?x Fe _x O_7?δ YBaCu_3?x Sn _x O_7?δ materials. These results can be interpreted as a consequence of the site preferences and the changes in the structure due to the presence of other additional substitutional elements.     

Collective states in even Sn nuclei

0⁺, 2⁺, 4⁴ and 3^? states in ^112–124Sn have been studied with the (p, p′γ) reaction and in Coulomb excitation. Absolute E2 transition rates between these levels have been extracted with the aid of the Winther-de Boer code. For ^116,118Sn, B(E2; 4₁⁺ → 2₁⁺) ≈ 20 W.u., suggesting a two-phonon character of the 4₁⁺ states. For the lighter and heavier isotopes, this value is significantly smaller. All observed values of B(E2; 2₂⁺ → 2₁⁺) and B(E2; 2₃⁺→ 2₁⁺) are about 5 W.u. Also. values of B(E3; 0₁⁺ → 3^?₁) have been measured for all stable even Sn nuclei. In ¹¹⁶Sn the branching ratio (3₁^? → 0₁⁺)/(3₁^? → 2₁⁺) has been measured. From this we obtain a half-life of 0.34±0.07 ps for the first 3^? level in ¹¹⁶Sn and B(E1; 3₁^? → 2₁⁺) = (1.4±0.3) × 10^?5'e² · b, corresponding to a hindrance factor of 10³.     

CEMS and SEM studies of the ion-beam mixed Ni−Sn and Al−Sn systems

Metallic¹¹⁹Sn was vapour deposited on Al and Ni substrates to form layers about 40nm thick and subsequently irradiated with 100keV Xe⁺ at fluences 1, 5 and 10·10¹⁵ Xe⁺/cm². Irradiation with 100keV N⁺ at 5·10¹⁶N⁺/cm² fluence was also accomplished on an Al sample on which a layer of 100nm¹¹⁹Sn was previously electrodeposited. Surface evolution of the deposited layers due to irradiation has been observed by SEM and loss of Tin due to sputtering has been evidenced by EDX microanalysis. Changes of chemical structure at the irradiated surfaces have been followed by CEMS: β-Sn, SnO, SnAl₂O₄, SnO₂ and SnAl₂O₅ or β-Sn, dissolved Tin in Nickel, SnO₂, Ni₃Sn and Ni₃Sn₂ phases were recognized on the surface of Aluminium and Nickel substrates respectively.     

High-spin states in107Sn

High-spin states in¹⁰⁷Sn were studied using the reaction⁵⁴Fe(⁵⁶Fe, 2pn)¹⁰⁷Sn. An odd-parity band was identified as based on thevh _11/2 orbit by measuring theγ-ray linear polarization. Also were confirmed the excited states based on thevd _5/2 andvg _7/2 orbits. The halflives of the 17/2⁺ and 11/2^? states were measured to be 0.25(4) ns and 28(11) ps, respectively. The experimental level structure and its interpretation were in good agreement with a shell model calculation.     

119Sn Mössbauer study of nickel–tin anodes for rechargeable lithium-ion batteries

¹¹⁹Sn Mössbauer spectrometry has been carried out on Ni–Sn alloys (Ni₃Sn LT, Ni₃Sn₂ LT and Ni₃Sn₄) and combined with ab initio calculations. Lithium insertion/extraction mechanisms of the most interesting compound (Ni₃Sn₄) have been studied from ¹¹⁹Sn Mössbauer measurements. The first discharge shows a plateau close to 0.0 V, which can be attributed to the formation of the Li₇Sn₂ alloy.     

The structure of 113Sn from proton and alpha- particle induced reactions

The results of in-beam investigations of ¹¹³ Sn using the (p,n), (p,3n), (α,n) and (α,2n) reactions are summarized. Excited states have been identified until E _x = 4715 MeV and J ^π = (27/2^{t -}). For a large number of levels mean lifetimes τ have been determined with the DSA method. For the J ^k = 25/2⁺ state at E _x = 4059 MeV, τ = 1.0(4) ns has been measured with the γ-RF method. The experimental results are compared with the predictions of shell-model calculations. Most of the positive-parity states may be considered as one-or three-quasiparticle neutron excitations of the 2d_5/2, 1_g7/2, 3_s1/2 and 2d_3/2 shells, the negative-parity states as the coupling of one 1h_11/2 neutron to the two- or four-quasiparticle neutron excitations in the even-mass ¹¹²Sn core. For the 25/2⁺ isomer the three-quasiparticle neutron configuration ν(h ₁₁ ^2/2 g ₇ ^2/?1 ) has been proposed on the basis of a shell-model analysis using the mass-formula formalism. The experimentally observed yrast states in ₅₀ ¹¹³ Sn₆₃ are compared with the corresponding states in the valence mirror nucleus ₆₃ ¹⁴⁵ Eu82 giving remarkable similarities although the parameters for the shell-model calculations differ considerably. The analysis of nearest-neighbour spacing distributions of experimentally obtained 5/2⁺ states in ¹¹³Sn does not allow definite conclusions about regularity or chaos.     

Local environment of Te in GaTe and Ga2Te3 studied with119Sn and129I Mössbauer spectroscopy

The compounds GaTe and Ga₂Te₃ have been studied with Mössbauer source spectroscopy, using the decays^119mTe→¹¹⁹Sb→¹¹⁹Sn and^129mTe→¹²⁹I. For Ga₂Te₃, which has a defect zincblende structure, the spectra give satisfactory fits using two components with intensity ratio roughly 2∶1, in agreement with the two crystallographic sites in this compound. The Mössbauer spectra of GaTe are not easily understood in terms of the three inequivalent Te sites present in this compound. The relevance of these results for the interpretation of Mössbauer spectra observed after high-dose Te implantation in GaAs is discussed.     

Local magnetic structure and anomalies of magnetic hyperfine interactions of57Fe and119Sn nuclei in lithium aluminium ferrites

The⁵⁷Fe and¹¹⁹Sn Mossbauer spectra of ordered ferrites Li_0.5Fe_2.5−xAl_xO₄∶Sn for 0.8<x<1.0 (the compensation point region) have been studied. The spin glass type magnetic structure with the spin canting angle depending on temperature and aluminium concentration is established. Anomalies in the temperature dependence of the hyperfine magnetic field at tin nuclei have been found near the compensation point of the ferrites     

Self-assembling of C and Sn in Ge

Self-assembling of isoelectronic C and Sn impurities in Ge is predicted. The formation of the 1C4Sn tetrahedral cells is thermodynamically profitable in Ge-rich C_xSn_yGe_1−x−y (4x<y) alloys in the ultra dilute C impurity limit with 1×10^-8x1×10^-3. The concentrations of Sn atoms when all C atoms are surrounded only by Sn atoms are estimated for the lower molecular beam epitaxy, intermediate annealing and higher bulk crystallization temperatures. The origin of this phenomenon is a considerable decrease of the strain energy after self-assembling. The same self-assembling in Si is thermodynamically non-profitable due to the large cohesive energy of Si–C chemical bonds.     

Radiative lifetime measurements of odd-parity high-excited levels of Sn I by time-resolved laser spectroscopy

Natural radiative lifetimes of five higher-lying odd-parity levels 5p7s ³P₁^o, 5p5d ¹P₁^o, 5p6d ³F₂^o, ³D₁^o and ³F₃^o in neutral tin are measured by the time-resolved laser-induced fluorescence (TR-LIF) technique and the atomic beam method. All these lifetimes are not longer than 100 ns and they are found to be shorter than the lifetimes of even-parity levels in the same energy region. The results reported in this paper provide important transition parameters for highly-excited atomic Sn, which may be useful for theoretically calculating excited heavy atoms.     

Determination of the oscillator strengths of Sn(I) in the ultraviolet (2400–4000 Å)

The emission spectrum of Sn(I) generated in a direct current arc plasma (Ar-SnCl₄ mixture) has been studied. The relative socillator strengths were obtained in the u.v. spectral range (2400–4000 Å) from measurements of branching ratios and from the study of radial temperature distribution and radial emission coefficients obtained by side-on measurement. These relative oscillator strengths were converted to an absolute scale by using as reference the lifetime determination of the ³P₁⁰ state. The results are compared with other absolute measurements.     

Preparation and critical currents of vapour-deposited Nb3Sn compound

Conclusion The presented results have shown that by optimizing some of the basic technological parameters of the chemical vapour-deposition process it is possible to increase substantially the critical currentI _c and the Nb₃Sn layer thickness of the produced superconductor without any other technological treatment.The critical currentI _c reported byEnstrom et al. [7] concerning the pure reaction atmosphere without doping gases, is about 13 A/mm (per 1 mm of the tape width), in our case it is 62 A/mm in transverse magnetic field of 5 T. We have shown that as far as the Nb₃Sn tape length of the order of 100 m is concerned, it seems more advantageous to work with Nb/Sn chlorides ratio for the region of 0·55 to 0·87 in contrast to the value of 0·33 reported byEnstrom et al. [7]. As we have already mentioned, further increase of theI _c andJ _c values may be achieved by means of doping gases injection into the reaction atmosphere or by additional heat treatment [11] etc.As it is also reported byEnstrom et al. [7], by doping the gaseous ambient with 0·1% CO₂, the increase ofI _c from 13 A/mm to 84 A/mm in the magnetic field of 5 T may be obtained. As the preliminary results of our investigation have shown, an increase from 32 A/mm to 106 A/mm by using the doping gases may be achieved for the tape travelling velocity of 4 m/h, the Nb/Sn chlorides ratio equal to 0·55 and the substrate heating current of the value of 4 A.We expect that by optimizing the technological parameters mentioned above together with following doping and additional heat treatment, we may obtain a substantial increase in theI _c andJ _c values.     

Dynamic disorder in solid tetrakis(trimethylstannyl)methane, C(SnMe3)4, investigated by one- and two-dimensional variable-temperature119Sn and13C NMR spectroscopy

Modes of molecular reorientation in solid tetrakis(trimethylstannyl)methane, C(SnMe₃)₄, have been investigated by one- and two-dimensional¹³C and¹¹⁹Sn static and magic-angle spinning nuclear magnetic resonance spectroscopy (NMR) in the temperature range from 150 to 290 K. Spectral lineshape fitting of one- and two-dimensional¹¹⁹Sn NMR experiments shows the pseudo-fivefold disorder previously observed by single-crystal X-ray diffraction on C(SnMe₃)₄ to be dynamic disorder (activation energy E_a ? 32 kJmol^?1). A dynamic-disorder model where each tin atom in a C(SnMe₃)₄ molecule occupies the twenty sites of a nearly perfect pentagonal dodecahedron with equal probability agrees best with the experimental solid-state NMR results.     

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.     

Temperature-Dependent Solid-State 119Sn- MAS NMR of Nd2Sn2O7, Sm2Sn2O7, and Y1.8Sm0.2Sn2O7. Three Sensitive Chemical-Shift Thermometers

The ¹¹⁹Sn MAS NMR resonances of the paramagnetic stannates Ln₂Sn₂O₇ (Ln = Nd, Sm, and Y_1.8Sm_0.2) have been found to be extremely sensitive to temperature, the isotropic resonances varying, at room temperature, by 14 and 1.1 ppm K^−l for Nd₂Sn₂O₇ and Sm₂Sn₂O₇, respectively. This sensitivity has been exploited to develop three chemical-shift thermometers with reciprocal dependences on temperature. Sm₂Sn₂O₇ is suitable for temperature calibration of standard MAS probes and the solid solution Y_1.8Sm_0.2Sn₂O₇ is a shift thermometer with an internal reference. Nd₂Sn₂O₇ is proposed as a high-temperature shift thermometer. These thermometers were used to determine the changes in sample temperature, in a Bruker 7 mm double-bearing probe, as the MAS speed was varied. A change of 8.5 K was observed on increasing the MAS speed from 1 to 5 kHz. The short relaxation times of the ¹¹⁹Sn nuclei enabled short recycle times to be used, and spectra of Sm₂Sn₂O₇ could be obtained in seconds.     

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.