First determination of isotopically invariant parameters of the negative ion—Hydrogen sulfide anion (SH)

The first isotopically invariant Dunham analysis of a negative ion (the hydrogen sulfide anion SH⁻) that uses all available infrared and sub-millimeter wave experimental data on ³²SH⁻, ³³SH⁻, ³⁴SH⁻, and ³²SD⁻ yields accurate information on Born-Oppenheimer breakdown parameters. The potential constants of expansion of the potential function up to the sixth order were calculated. Differences between the construction of the potential function based on the Morse potential and that on the base of the power series expansion are shown.     

The <Emphasis Type="Italic">A</Emphasis> dependence of proton yields in the absorption reaction of stopped π<Superscript>−</Superscript> mesons

Experimental results on the yields and spectra of protons produced during the absorption of stopped pions by nuclei are presented. The measurements were performed on the accelerator at the St. Petersburg Nuclear Physics Institute, Russian Academy of Sciences, using a two-arm semiconductor spectrometer of charged particles on a set of nuclei that includes light nuclei ^6,7Li, ⁹Be, ^10,11B, and ¹²C; medium nuclei ²⁸Si, ⁴⁰Ca, ⁵⁹Co, and ⁹³Nb; tin isotopes ^{114,117,120,124}Sn; and heavy nuclei ¹⁶⁹Tm, ¹⁸¹Ta, and ²⁰⁹Bi. The A dependences of the proton yields and their components are obtained. Some indications of the dominant role of pion absorption on intranuclear pp pairs in the formation of fast protons are presented.     

Shape effects in heavy ion (Li) elastic scattering

The elastic scattering of aligned ⁶Li and ⁷Li on ⁵⁸Ni at E_cm = 12.7 MeV displays an “isotopic” effect which can be traced to the very different (mass) quadrupole moments of both isotopes. The elastic scattering of aligned ⁶Li and ⁷Li on ^12,13C at E_Li = 9 MeV displays large effects, but the angular dependence is much more complicated compared to the scattering on ⁵⁸Ni.     

Dynamic polarization in the Coulomb breakup of loosely bound F

Angular distributions of the Coulomb breakup of radioactive ¹⁷F were measured by impinging a 10 MeV/nucleon beam on ²⁰⁸Pb and on ⁵⁸Ni to study the dynamic polarization effects. The breakup products, oxygen and a proton, were detected in coincidence. First-order perturbation theory significantly overpredicts the breakup cross section for the ²⁰⁸Pb target. Dynamical calculations with a dynamic polarization as the leading order correction were performed. The calculations reproduce the data for ¹⁷F on ⁵⁸Ni but overpredict the breakup of ¹⁷F on ²⁰⁸Pb by a factor of two at forward angles.     

Inelastic scattering of 12C and 13C on 63Cu leading to core-excited states

The inelastic scattering of ¹²C and ¹³C projectiles has been studied on ⁶³Cu at 45 MeV incident energy. The core-excited states (based on 2⁺ in ⁶²Ni) show individual differences in the angular distributions which are due to second-order couplings (transfer and inelastic transitions). However, the sum of the core-excited states yields the same cross section as observed in the inelastic scattering of ¹²C at 48 MeV on ⁶²Ni (2⁺).     

Nuclear molecules in ternary fission

Experimental results on particle accompanied cold fission of ²⁵²Cf suggest the existence of a short-lived quasi-molecular state. Within our three-center phenomenological model, described in this paper, we found a possible explanation based on a new minimum in the deformation energy at a separation distance very close to the touching point. Half-lives of some quasimolecular states which could be formed in ¹⁰Be accompanied fission of ²³⁶U, ²³⁶Pu, ²⁴⁶Cm, ²⁵²Cf, ^252,256Fm, ^256,260No, and ²⁶²Rf are roughly estimated.     

Outer-Sphere Interaction in Hexafluorocomplexes of Elements of Group IV with Cations of Alkali Metals and Ammonium

IR-absorption spectra of M²AF⁶hexafluorocomplexes (M-Na, K, Rb, Cs and NH⁴; A=Si, Ge, Sn) were obtained and intergrated intensities of bands assigned to stretching vibrations of AF⁶ ions were measured. The reasons for the influence of exchange of the central atom and an outer-sphere cation on the intergrated intessities of vibration bands are discussed. It was found that the ammonium ion does not fit into the earlier established pattern of intensity dependence on cation size. Analysis of the frequencies v³ (AF⁶) suggeste that this is coused by the presence in (NH⁴)²AF⁶ of hydrogen bonds N-H F of different strength.

The question of the influence of anther-sphere cation on the spectral properties of complex compounds has been treated in the literature ^1-6. The dependence of vibrational frequencies characterizing the anion ^1-3, the integrated intensity vibration bands (IIVB) in IR-absorption spectra ⁴, chemical shiftn in ¹⁹ f NMR apectra ² and the luminescent properties of complexed on cation nature have been established.     

The (π+π−), (π+ K −), (π− Σ+), (K + K −), and(\overline {\Sigma ^ + } \Sigma ^ + ) Atomic States

The expected energy shifts are calculated for the (π ⁺ π ^?), (π ⁺ K ^?), (π ^? Σ ⁺), and (K ⁺ K ^?) atomic states on the basis of the existing information on the corresponding scattering lengths.     

<Emphasis Type="Italic">J</Emphasis><Superscript>π</Superscript>0<Superscript>−</Superscript> levels in <Superscript>156</Superscript>Gd and <Superscript>158</Superscript>Gd

The 0^? states in the ¹⁵⁶Gd nucleus at E = 1952.38 keV and in the ¹⁵⁸Gd nucleus at E = 2269.16 keV are established on the basis of an analysis of available data on even-even deformed nuclei. From data on the deexcitation of the levels and on the probability of their population by beta transitions, it is found that these states have a two-particle proton structure. A comparison of our data with information about the 0^? levels in the ¹⁷⁰Yb and ¹⁷⁶Hf nuclei makes it possible to conclude that J^π0^? two-particle states exist at an excitation energy of about 2 MeV and higher.     

Partial fusion of a weakly bound projectile with heavy target at energies above the Coulomb barrier

Partial-fusion cross-sections for the systems ⁶Li + ²⁰⁸Pb, ⁹Be + ²⁰⁹Bi have been determined. The effect of breakup on fusion for weakly bound projectiles ⁶Li and ⁹Be incident on ²⁰⁸Pb or ²⁰⁹Bi targets has been discussed comparing experimental fusion cross-section excitation functions to those evaluated with a semi-classical approach. It is shown that complete fusion of a weakly bound projectile with heavy target is reduced, whereas the breakup process has very little influence on the total-fusion cross-section for some of the studied systems at energies above the Coulomb barrier.     

Detailed spectroscopy of doubly-magic 132Sn and its neighbours; Perspective for further studies at PIAFE

Experimental studies at the OSIRIS fission-product mass separator have yielded a wealth of new results on the doubly-magic region near ¹³²Sn. In the following we focus on two aspects of the new results: on the evidence for octupole collectivity of the 3₁⁻ state in ¹³²Sn and on the similarity of the ²⁰⁸Pb and ¹³²Sn regions as evidenced from the modelling of the low excitations in ¹³²Sb. The Stage-I of the PIAFE facility recently proposed at Grenoble will offer exciting possibilities for even more detailed studies of the doubly magic regions near ¹³²Sn and ⁷⁸Ni (the latter for the first time).     

A study of three-nucleon transfer reactions on 17O

The reactions ¹⁷O(¹¹B, ⁸Li)²⁰Ne, ¹⁷O(¹²C, ⁹Be)²⁰Ne and ¹⁷O(¹³C, ¹⁰B)²⁰F have been studied using beams of 115 MeV ¹¹B and ¹²C and 105 MeV ¹³C incident on a gas target. Shell-model calculations have been performed for ²⁰Ne and ²⁰F, for comparison with the experimental data. It is found that the data can be interpreted using the shell model spectroscopic factors and a semi-classical reaction theory. We justify the use of the latter by applying it to the cases of three-nucleon transfer on ¹⁶O. Spin assignments are suggested for previously unidentified states in ²⁰F.     

Elastic scattering and total reaction cross section for the He + Al system

The elastic scattering of the radioactive halo nucleus ⁶He on ²⁷Al target was measured at four energies close to the Coulomb barrier using the RIBRAS (Radioactive Ion Beams in Brazil) facility. The São Paulo Potential (SPP) was used and its diffuseness and imaginary strength were adjusted to fit the elastic scattering angular distributions. Reaction cross-sections were extracted from the optical model fits. The reduced reaction cross-sections of ⁶He on ²⁷Al are similar to those for stable, weakly bound projectiles as ^6,7Li, ⁹Be and larger than stable, tightly bound projectile as ¹⁶O on ²⁷Al.     

Effect of salinity on the concentrations of radioisotopes in the aquatic environment of a hypersaline coastal lagoon

Research of the effect of salinity on the fate of radionuclides has been focused on seas or estuarine systems while there is almost no information on marine environments with a salinity higher than that of sea water. The hypersaline Bardawil lagoon is a concentration basin, with evaporation exceeding precipitation. This study presents the characteristics of some environmental factors including salinity and their influence on the distribution of natural and artificial radionuclides in different compartments of the lagoon. The concentrations of ²³⁸U, ²³⁴Th, ²²⁸Ra and ¹³⁷Cs in sediments show some degree of dependency on the water's salinity. Migration of these radionuclides in the lagoon's sediments must take place from high salinity to low-salinity regions. Cluster analysis revealed the data structure for sediment by separating ¹³⁷Cs and ⁴⁰K from ²³²Th, ²²⁶Ra, and ²³⁴Th and for sand by separating ⁴⁰K from the other radioisotopes.     

Ce3+对Er3+/Yb3+共掺氟磷酸盐玻璃光谱性质的影响

研究了能量接受离子Ce³⁺对Er³⁺上转换发光强度以及Er³⁺在1.5μm附近波段发光性能参数的影响，并从能量匹配及能级结构角度出发对Er³⁺/Ce³⁺间的能量转移机制进行了分析.分析认为，⁴I_11/2能级的Er³⁺通过无辐射能量转移把能量传递给²F_5/2能级的Ce³⁺关键词： 氟磷酸盐玻璃 光谱性质 光纤放大器 3+和Ce³⁺')" href="#">Er³⁺和Ce³⁺     

Dependence of critical pitting temperature on the concentration of sulphate ion in chloride-containing solutions

Effects of varying concentration of sulphate (SO₄²⁻) ion on the pitting behavior of 316SS have been investigated using potentiostatic critical pitting temperature (CPT) measurements, potentiostatic current transient technique and scanning electron microscopy in NaCl solution containing 0.5% Cl⁻ ions. The results demonstrated that when the concentration of SO₄²⁻ ion is less than 0.42%, the CPT is surprisingly lower than that without SO₄²⁻ ion, showing an accelerating effect of the SO₄²⁻ ion on pit initiation, which is different from the traditional concept. As the concentration of SO₄²⁻ ion increases beyond 0.42%, the CPT is higher than that without SO₄²⁻ ion, displaying an inhibiting effect of the SO₄²⁻ ion on pit initiation. Based on the above results, a qualitative model is proposed to explain the inhibiting and accelerating effect of SO₄²⁻ ion on the pit initiation using the mechanism of ions-competitive adsorption between SO₄²⁻ and Cl⁻ ions. The electric charges calculated in the process of pitting corrosion indicated that the pit morphology and its dimension are dependent on the content of SO₄²⁻ ion in chloride-containing solutions. The higher the concentration of SO₄²⁻ ion, the larger the dimension of the pit, reflecting an accelerating effect on pit growth.     

New results on elements 111 and 112

Experiments on the synthesis and identification of the nuclei ²⁷²111 and ²⁷⁷112 were performed in order to confirm previous results. Three additional decay chains were measured in the reaction ⁶⁴Ni + ²⁰⁹Bi →²⁷³111^*. The study revealed considerably improved data on the decay chain originating from ²⁷²111. One additional chain was measured in the reaction ⁷⁰Zn + ²⁰⁸Pb →²⁷⁸112^*. The decay properties of the chain starting at ²⁷⁷112 are in excellent agreement with the second chain of the first experiment down to ²⁶⁵Sg, where the new chain ends by a previously unknown spontaneous-fission branch. A re-analysis of all the data on elements 110, 111, and 112 measured at GSI since 1994 (a total of 34 decay chains was investigated) revealed that for 2 chains (the second chain of ²⁶⁹110 measured in 1994 and the first chain of ²⁷⁷112 measured in 1996) the results of the new analysis differed from the previous one. In all other cases the earlier data are exactly reproduced. Received: 21 December 2001 / Accepted: 15 January 2002     

Contributions of excited 6Li and 7Li nuclei to the production of 4He+2H and 4He+3H systems in 16O p collisions at a momentum of 3.25 GeV/c per nucleon

New experimental data on the cross sections for the yield of excited ⁶Li* and ⁷Li* nuclei and on their contributions to the production of ⁴He + ²H and ⁴He+³H light dinuclear systems in ¹⁶O _p collisions at a momentumof 3.25 A GeV/c per nucleon are presented.     

Study of some rare decays of the K+ meson

In a search for very rare decays of the K⁺ meson we observed the K⁺→μ⁺νe⁺e^? and K⁺→e⁺ν e⁺e^? modes with branching ratios of (10±3) ×10^?7 and (2⁺²_?2)×10^?7 respectively. We also put new limits on a decay allowed by the alternate scheme of lepton conservation K⁺→π^?μ⁺e⁺, on a decay with double charged weak current K⁺→π^? e⁺e⁺ and on other forbidden decays K⁺→μ^?νe⁺e⁺ and K⁺→π⁺μ^±e^±.     

Effects of inelastic multistep processes on (p,t) reactions in a transition region between rare-earth nuclei and double-magic 208Pb

Effects of inelastic multistep processes on (p, t) reactions in a transition region between well-deformed rare-earth nuclei and the double-magic ²⁰⁸Pb have been investigated by the ¹⁸⁸Os(p, t) ¹⁸⁶0s, ^{194, 196}Pt(p, t)^{192, 194}Pt and ^{200, 202}Hg(p, t)^{198, 200}Hg reactions at E_p = 51.9 MeV. The observed ground 0⁺, first excited 2⁺ and 4⁺ angular distributions together with those for the ^{206, 208}pb(p, t)^{204, 206}pb reactions have been compared with CCBA and DWBA calculations, using transfer form factors based on the Nilsson, vibrational and shell models. It is found that the inelastic multistep processes play a very important role in reproducing both the shapes and magnitudes of the observed first excited 2⁺ angular distributions, contrasting to small contributions in the ground-state 0⁺ transitions. The effects of the inelastic multistep processes on the first excited 4⁺ transitions are also considered to be important.