Magic nucleus 132Sn and its one-neutron-hole neighbor 131Sn

Prompt and delayed gamma-ray cascades in doubly magic 132Sn and its neighbor 131Sn have been studied at Gammasphere using a 248Cm fission source. Isotopic assignments of unknown gamma rays were based on coincidences with known transitions in A = 112-116 Pd fission partners. The yrast level spectra of both tin nuclei are interpreted using empirical nucleon-nucleon interactions from the 132Sn and 208Pb regions. Results include identification of the (nuf(7/2)h(-1)(11/2))9(+) aligned state in 132Sn and of extensive (nuf(7/2)h(-2)(11/2)), (nuf(7/2)d(-1)(3/2)h(-1)(11/2)) and (nuh(-1)(11/2)x3(-)) multiplets in 131Sn. The previously reported beta(-) decay of an unusual 131In high-spin isomer to levels in 131Sn is also elucidated.     

0(gs)+ -->2(1)+ transition strengths in 106Sn and 108Sn

The reduced transition probabilities, B(E2; 0(gs)+ -->2(1)+), have been measured in the radioactive isotopes (108,106)Sn using subbarrier Coulomb excitation at the REX-ISOLDE facility at CERN. Deexcitation gamma rays were detected by the highly segmented MINIBALL Ge-detector array. The results, B(E2;0(gs)+ -->2(1)+)=0.222(19)e2b2 for 108Sn and B(E2; 0(gs)+-->2(1)+)=0.195(39)e2b2 for 106Sn were determined relative to a stable 58Ni target. The resulting B(E2) values are approximately 30% larger than shell-model predictions and deviate from the generalized seniority model. This experimental result may point towards a weakening of the N=Z=50 shell closure.     

在40MeV/u时112Sn+112Sn和124Sn+124Sn中多重碎裂的同位旋效应

利用同位旋相关的量子分子动力学模型,研究了112Sn+112Sn和124Sn+124Sn两个反应系统在入射能量E=40MeV/u时的多重碎裂.计算结果能与实验值定性符合.观察到两个反应系统中,中等质量碎片多重性、中子多重性、荷电粒子多重性与轻荷电粒子多重性之间的关联存在着明显的差别.另外,通过与膨胀蒸发源模型及同位旋相关的渗透模型分析结果的比较,发现这种差别主要是由同位旋相关的反应动力学所造成的.     

Disproportionation phenomena on free and strained Sn/Ge(111) and Sn/Si(111) surfaces

Distortions of the sqrt[3]x sqrt[3] Sn/Ge(111) and Sn/Si(111) surfaces are shown to reflect a disproportionation of an integer pseudocharge, Q, related to the surface band occupancy. A novel understanding of the (3 x 3)-1U ("1 up, 2 down") and 2U ("2 up, 1 down") distortions of Sn/Ge(111) is obtained by a theoretical study of the phase diagram under strain. Positive strain keeps the unstrained value Q=3 but removes distortions. Negative strain attracts pseudocharge from the valence band causing first a (3 x 3)-2U distortion (Q=4) on both Sn/Ge and Sn/Si, and eventually a (sqrt[3] x sqrt[3])-3U ("all up") state with Q=6. The possibility of a fluctuating phase in unstrained Sn/Si(111) is discussed.     

Evidence for pygmy and giant dipole resonances in 130Sn and 132Sn

The dipole strength distribution above the one-neutron separation energy was measured in the unstable 130Sn and the double-magic 132Sn isotopes. The results were deduced from Coulomb dissociation of secondary Sn beams with energies around 500 MeV/nucleon, produced by in-flight fission of a primary 238U beam. In addition to the giant dipole resonance, a resonancelike structure ("pygmy resonance") is observed at a lower excitation energy around 10 MeV exhausting a few percent of the isovector E1 energy-weighted sum rule. The results are discussed in the context of a predicted new dipole mode of excess neutrons oscillating out of phase with the core nucleons.     

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.     

Photodisintegration of Sn isotopes

Yields of (γ, n) reactions on tin isotopes ¹²⁴Sn, ¹¹⁸Sn, ¹¹⁴Sn, and ¹¹²Sn and yields of (γ, p) reactions on ¹¹⁷Sn, ¹¹⁶Sn, and ¹¹²Sn were measured in the present study. The obtained results are compared to those from earlier experiments and theoretical calculations. The yields of reactions with the production of nuclei in isomeric states are presented.     

Photo and electroluminescence of ZnSe: Sn and ZnSe:(Sn,Pr) phosphors

We have prepared ZnSe (luminescent grade) phosphor doped with Sn and (Sn,Pr) with varying concentration in an inert atmosphere in a silica tubular furnace at temperature of (780 ± 20) °C for 1 hr to obtain ZnSe:Sn and ZnSe: (Sn,Pr) phosphors. The photo luminescence (PL) and electroluminescence (EL) spectra of these phosphors have been studied at room temperature and results were discussed in the light of existing models. Dependence of EL emission on the voltage frequency has also been carried out. It is found that the plot between the integrated light intensity versus 1/√V_rms is a straight line suggesting the existence of Mott–Schottky type barrier on the metal semiconductor interface.     

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.     

Global properties of nuclei from 100Sn to 132Sn

The paper presents the results of both microscopical and semi-empirical calculations of single-particle characteristics, nuclear binding, and one-nucleon separation energies of nuclei, as well as their root-mean-square radii, energy levels and transition rates in the long chain of Sn isotopes. We consider nuclei from the extremely neutron-deficient ¹⁰⁰Sn up to neutron excess ¹³⁶Sn, where the experimental information is available by now. The comprehensive comparison with the experimental data is carried out.     

Beta decay of the proton-rich nuclei 102Sn and 104Sn

The β decays of ¹⁰²Sn and ¹⁰⁴Sn were studied by using high-resolution germanium detectors as well as a Total Absorption Spectrometer (TAS). For ¹⁰⁴Sn, with three new β-delayed γ-rays identified, the total Gamow-Teller strength (B_GT) value of 2.7(3) was obtained. For ¹⁰²Sn, the γ-γ coincidence data were collected for the first time, allowing us to considerably extend the decay scheme. This scheme was used to unfold the TAS data and to deduce a B_GT value of 4.2(8) for this decay. This result is compared to shell model predictions, yielding a hindrance factor of 3.6(7) in agreement with those obtained previously for ⁹⁸Cd and ¹⁰⁰In. Together with the latter two, ¹⁰²Sn completes the triplet of Z ⩽ 50, N ≥ 50 nuclei with two proton holes, one proton hole and one neutron particle, and two neutron particles with respect to the doubly magic ¹⁰⁰Sn core.     

Neutron elastic scattering from 116,118,120,122,124Sn

Accurate measurements of neutron differential elastic cross sections have been obtained from even isotopes of Sn. Data are presented for the elastic scattering of 11 MeV neutrons from ^{116, 118, 120, 122, 124}Sn, the elastic scattering for 24 MeV neutrons from ^{116, 118, 124}Sn and the neutron total cross section from ^{118, 120, 122, 124}Sn in the energy ranges 5.0–10.6 MeV and 20.0–26.0 MeV. The elastic scattering data are analyzed in terms of an empirical optical-model potential. The obtained optical-potential parameters are analyzed in terms of energy and isospin dependence and compared with those obtained from proton elastic scattering on even Sn isotopes.     

Ag−Sn Alloys and dental amalgams: A119Sn Mössbauer,x-ray diffraction and scanning electron microscopy study

Examination has been made on aged and fresh Ag?Sn alloys and on commercial Cu?Ag?Sn dental alloys. Although x-ray diffractograms of aged Ag?Sn showed only λ Ag?Sn and free silver,¹¹⁹Sn Mössbauer spectra exhibited Sn(IV) oxide also. A low Debye temperature showed the oxide to be in intimate dynamical contact with the metallic matrix. Upon adding mercury, the phases λ₁ Ag?Hg and η′ Cu?Sn were observed in a commercial specimen. Conversion-electron spectra of a mercury-coated disk showed the presence of λ₂ Sn?Hg and a distribution of line positions smaller than that for particulate amalgams. Internal oxidation was found to prevent amalgamation.     

119Sn Mössbauer Study of as-Deposited Layers Prepared by Co-evaporation of TeO2 and Sn

The deposited layers on glass surface with thickness between 230 and 500 nm were prepared by the chemical reactions of TeO₂ and Sn during vacuum co-deposition, and were characterized as a function of the Sn/Te ratio between 0.5 and 2.8 by ¹¹⁹Sn conversion electron Mössbauer spectroscopy. The as-deposited samples showed amorphous character with very finely dispersed microstructure. The ¹¹⁹Sn Mössbauer spectra of as-deposited samples revealed the dominance of Sn(II) and Sn(IV) states although SnTe was also found when the Sn/Te ratio was high. A monotonous increase of the Sn(II)/Sn(IV) ratio was observed with increasing Sn/Te ratio.     

Interactions at the planar Ag3Sn/liquid Sn interface under ultrasonic irradiation

The interactions at the interface between planar Ag₃Sn and liquid Sn under ultrasonic irradiation were investigated. An intensive thermal grooving process occurred at Ag₃Sn grain boundaries due to ultrasonic effects. Without ultrasonic application, planar shape of Ag₃Sn layer gradually evolved into scalloped morphology after the solid-state Sn melting, due to a preferential dissolution of the intermetallic compounds from the regions at grain boundaries, which left behind the grooves embedding in the Ag₃Sn layer. Under the effect of ultrasonic, stable grooves could be rapidly generated within an extremely short time (<10 s) that was far less than the traditional soldering process (>10 min). In addition, the deepened grooves leaded to the formation of necks at the roots of Ag₃Sn grains, and further resulted in the strong detachment of intermetallic grains from the substrate. The intensive thermal grooving could promote the growth of Ag₃Sn grains in the vertical direction but restrain their coarsening in the horizontal direction, consequently, an elongated morphology was presented. All these phenomena could be attributed to the acoustic cavitation and streaming effects of ultrasonic vibration.     

激光烧蚀-快脉冲放电等离子体光谱技术分析土壤中的Sn

采用一种新发展中的激光烧蚀-快脉冲放电等离子体光谱技术首次检测土壤中Sn元素的浓度.与传统的激光诱导击穿光谱技术相比,采用激光烧蚀-快脉冲放电等离子体光谱技术所产生的Sn(284.0 nm)元素辐射光谱强度有很大提高,并应用该技术获得了土壤中Sn元素的校准曲线,使土壤中Sn元素检测极限降低到0.16 μg·g-1.与各...     

Formation of the Cu6Sn5 Intermetallics in Cu/Sn Thin Films

Physics of the Solid State - The formation of the Cu6Sn5 intermetallic in Sn(55nm)/Cu(30nm) thin-film bilayers has been studied upon heating the film sample from room temperature to 300°C...     

Effect of adsorbed Sn on Ge diffusivity on Si(111) surface

The effect of adsorbed Sn as a surfactant on Ge diffusion on a Si(111) surface has been studied by Low Energy Electron Diffraction and Auger Electron Spectroscopy. The experimental dependence of Ge diffusion coefficients on the Si(111) surface versus temperature in the presence of adsorbed Sn atoms has been measured in the range from 300 to 650°C. It has been shown that at a Sn coverage of about 1 monolayer the mobility of Ge atoms increases by several orders of magnitude.      

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.     

Directed and elliptic flows in 40Ca + 40Ca and 112Sn + 112Sn collisions

The directed and elliptic flows for different light particles and fragments in collisions of ⁴⁰Ca + ⁴⁰Ca and ¹¹²Sn + ¹¹²Sn at energies from 30MeV/nucleon to 100MeV/nucleon were studied in the isospin-dependent quantum molecule dynamics model (IQMD). With increasing incident energy, the directed flow rises from negative to positive, while the elliptic flow decreases with increasing the incident energies. The directed flow for the ⁴⁰Ca + ⁴⁰Ca system is not sensitive to the nuclear equation of states (EOS), but the directed flow for the ¹¹²Sn + ¹¹²Sn system is sensitive to the EOS. However, the elliptic flows for both ⁴⁰Ca + ⁴⁰Ca and ¹¹²Sn + ¹¹²Sn systems are not sensitive to EOS. A study of the dependence of directed and elliptic flows on the fragment charge (mass) is also performed. Received: 15 March 2002 / Accepted: 14 June 2002 / Published online: 19 November 2002 RID="a" ID="a"e-mail: Zhanghy@sinr.ac.cn; Permanent address: Shanghai Institute of Nuclear Research, Chinese Academy of Sciences, P.O. Box 800-204(2), Shanghai 201800, China. Communicated by W. Henning