TheN=83 nucleus149Dy from Gamow-Teller decay of its 11/2− and 1/2+ 149Ho parents

A high-sensitivityγ-spectroscopic study of the¹⁴⁹Hoπh _11/2 andπs _1/2 β-decays using mass separated sources has located dominant 0⁺ → 1⁺ GT decay strength associated with decay of pairedh _11/2 protons, leading to 3п-states in the¹⁴⁹Dy daughter nucleus. In theirγ-decay low-lying¹⁴⁹Dy levels characteristic of anN=83 nucleus are excited. They include theνf _7/2,νp _3/2,νh _9/2 andνp _1/2 single particle- and theνs ₁ ^2/?1 andνd ₃ ^2/?1 two-particle one-hole states, as well as the νf _7/2 × 3^? andνf _7/2 × 2⁺ particle-phonon multiplets. A synopsis is given of these excitations in theN=83 isotones from¹⁴⁹Nd to¹⁵³Yb. The¹⁴⁹Dy GT decay strength is discussed in terms of the¹⁴⁷Tb₈₂ and¹⁴⁸Dy₈₂ decays. The strength function results are also compared with independent¹⁴⁹Ho 11/2^? decay data from the literature based on totalγ-ray absorption measurements.     

Structure of the highly deformed nucleus101Sr63 and evidence for identical K=3/2 bands

The low-energy level scheme of theN=63 nucleus¹⁰¹Sr has been obtained from a β-decay study of¹⁰¹Rb. The ν[532]5/2 and ν[411]3/2 orbitals are well established as the ground state and a band head at 271.2keV, respectively. The general properties of the level scheme indicate a quadrupole deformation ofβ ? 0.4, confirming the unique feature of saturation of deformation inN ≥ 60 Sr isotopes. The energies of theK=3/2 intraband transitions in the odd-neutron neighbours⁹⁹Sr₆₁ and¹⁰¹Sr₆₃ are very similar. More generally, the identical bands at low spin in^98–101Sr nuclei are correlated with the mass-independent moments of inertia in this region.     

Isomere Wirkungsquerschnittsverhältnisse beim thermischen Neutroneneinfang im Bereich der 2p 1/2 und 1g 9/2 Schalenmodellzustände

Thermal capture cross sections and isomeric cross section ratios in thermal neutron capture were determined for even-even nuclei in the region of the 2p _1/2-1g _9/2 neutron shell. Capture cross sections for formation of Zn 69 ^m , Zn 71 ^m , Zn 71, Ge 71, Ge 75 ^m , Ge 77 ^m , Se 77 ^m , Se 79 ^m , Se 83 ^m , Se 83, Sr 85 ^m and Sr 87 ^m were measured by the activation method. From these data and additional measurements of cross section ratios the isomeric ratios for thermal capture in Zn 68, Zn 70, Ge 70, Ge 74, Ge 76, Se 76, Se 78, Se 80, Se 82 and Sr 84 were determined. In addition epithermal capture isomer ratios were determined for Zn 68, Ge 74, Ge 76, Se 80 and Sr 84. The isomer ratios are compared with calculations based on the statistical model ofHuizenga andVandenbosch. With the exception of Se 80 the measured ratios can be explained theoretically with reasonable values of the spin-cutoff-factorσ and gamma-ray multiplicityN, however there seems to be unexplained difference in eitherσ orN between the two groups of nuclei leading to either 1/2–7/2 or 1/2–9/2 isomers.     

High-pressure Raman spectroscopic studies on orthophosphates Ba3(PO4)2 and Sr3(PO4)2

By using diamond anvil cell (DAC), high-pressure Raman spectroscopic studies of orthophosphates Ba₃(PO₄)₂ and Sr₃(PO₄)₂ were carried out up to 30.7 and 30.1 GPa, respectively. No pressure-induced phase transition was found in the studies. A methanol:ethanol:water (16:3:1) mixture was used as pressure medium in DAC, which is expected to exhibit nearly hydrostatic behavior up to about 14.4 GPa at room temperature. The behaviors of the phosphate modes in Ba₃(PO₄)₂ and Sr₃(PO₄)₂ below 14.4 GPa were quantitatively analyzed. The Raman shift of all modes increased linearly and continuously with pressure in Ba₃(PO₄)₂ and Sr₃(PO₄)₂. The pressure coefficients of the phosphate modes in Ba₃(PO₄)₂ range from 2.8179 to 3.4186 cm⁻¹ GPa⁻¹ for ν₃, 2.9609 cm⁻¹ GPa⁻¹ for ν₁, from 0.9855 to 1.8085 cm⁻¹ GPa⁻¹ for ν₄, and 1.4330 cm⁻¹ GPa⁻¹ for ν₂, and the pressure coefficients of the phosphate modes in Sr₃(PO₄)₂ range from 3.4247 to 4.3765 cm⁻¹ GPa⁻¹ for ν₃, 3.7808 cm⁻¹ GPa⁻¹ for ν₁, from 1.1005 to 1.9244 cm⁻¹ GPa⁻¹ for ν₄, and 1.5647 cm⁻¹ GPa⁻¹ for ν₂.     

Elastic scattering of20Ne on24Mg

High spin states in⁸⁵Rb and⁸⁵Sr were populated in the reactions⁷⁶Ge(¹²C,p2n) and⁷⁶Ge(¹²C,3n), respectively. The lifetimes of twelve states were measured via the recoil distance Doppler shift technique. The positive parity bands in both nuclei associated with theg _9/2 orbit exhibit decrasingE2 strengths for increasing spin value marking the onset of multiparticle excitation.     

Diffusion theory of the positive column with two-stage ionization and collisional deexcitation

The diffusion theory of the low pressure positive column is extended to account for collisional deexcitation as well as for two-stage ionization by electron impact. This extension results in the equationn″(ξ)+n′(ξ)/ξ+n(ξ)+vn ²(ξ)[1+μn(ξ)]^-1=0, which is solved numerically for the value ofξ ₁ which satisfies the boundary conditionn(ξ ₁)=0 for different values of the parametersν andμ.     

Laser Stark and laser microwave double-resonance spectroscopy of deuterated fluoroacetylene with the CO2 laser

The CO₂ laser Stark spectrum of deuterated fluoroacetylene was identified with the aid of the double-resonance technique for the ν₃, ν₃ + ν₅ ? ν₅, ν₃ + ν₄ ? ν₄, ν₃ + 2ν₅ ? 2ν₅, and ν₃ + ν₄ + ν₅ ? ν₄ ? ν₅ vibrational bands. Laser microwave double-resonance signals were observed in the presence of the Stark field. From the analysis of the double-resonance signals precise values of the dipole moment were obtained for 10 vibrational states, in Debye, with the uncertainties in parentheses: ground, 0.73292(22); ν₅, 0.75656(17); ν₄, 0.68412(24); 2ν₅(Σ⁺), 0.78063(21); ν₄ + ν₅(Σ⁺ or Σ^?), 0.70698(19); ν₃, 0.75772(30); ν₃ + ν₅, 0.78270(18); ν₃ + ν₄, 0.70822(17); ν₃ + 2ν₅(Σ⁺), 0.80808(25); ν₃ + ν₄ + ν₅(Σ⁺ or Σ^?), 0.73329(17). The band origins were determined (in cm^?1); ν₃, 1045.9242(8); ν₃ + ν₅ ? ν₅, 1049.6441(8); ν₃ + ν₄ ? ν₄, 1047.8700(8); ν₃ + 2ν₅ ? 2ν₅(Σ⁺-Σ⁺), 1053.0374(8); ν₃ + ν₄ + ν₅ ? ν₄ ? ν₅(Σ⁺?Σ⁺ or Σ^??Σ^?), 1051.5040(8).     

蓝色荧光粉Sr2B5O9Cl:Eu2+发光特性的研究

采用高温固相法合成了近紫外光激发的蓝色荧光粉Sr₂B₅O₉Cl:Eu²⁺,研究了SrCl₂ ·6H₂O用量和Eu²⁺浓度对其结构和发光性能的影响.随着Eu²⁺浓度的增加,其结构无明显变化,发光强度先增强后减弱,当其浓度为8mol%时,荧光粉的发光强度最大;当用Ca取代Sr时,荧光粉的发射峰从425 nm红移到453 nm. 适当过量 关键词： 氯硼酸盐 蓝色荧光粉 LED     

Analysis of n(87Sr)/n(86Sr), δ88Sr/86SrSRM987 and elemental pattern to characterise groundwater and recharge of saline ponds in a clastic aquifer in East Austria

Elemental and isotopic pattern of n(⁸⁷Sr)/n(⁸⁶Sr) and δ⁸⁸Sr/⁸⁶Sr_SRM987 were used to characterise groundwater and recharge of saline ponds in a clastic aquifer in East Austria. Therefore, shallow, artesian and thermal groundwaters of the investigated aquifer along with rainfall and rivers were analysed using (MC) ICP-MS. The n(⁸⁷Sr)/n(⁸⁶Sr) ratio and elemental pattern changed with aquifer depth as a result of progressing bedrock leaching and dissolution with increasing groundwater residence time. The n(⁸⁷Sr)/n(⁸⁶Sr) ratio of shallow groundwater below saline ponds of 0.71019?±?0.00044 was significantly different from thermal groundwater of 0.71205?±?0.00035 (U, k?=?2). In contrast to previous theories, this result suggested no recharge of saline ponds by upwelling paleo-seawater. Isotope pattern deconvolution revealed that rainfall accounted to about 60% of the n(⁸⁷Sr)/n(⁸⁶Sr) ratio of shallow groundwater below saline ponds. The δ⁸⁸Sr/⁸⁶Sr_SRM987 values of groundwater decreased from about 0.25 ‰ in most shallow, to predominantly negative values of about –0.24 ‰ in artesian groundwater. This result indicated leaching and dissolution of weathered minerals. In turn, the δ⁸⁸Sr/⁸⁶Sr_SRM987 of deep thermal groundwater showed positive values of about 0.12 ‰, which suggested removal of ⁸⁶Sr from solution by carbonate precipitation. These results highlight the potential of δ⁸⁸Sr/⁸⁶Sr_SRM987 signature as an additional geochemical tracer.     

Experimentelle Untersuchungen am Elektroneneinfang des85Strontium und88Yttrium

The electron capture decay of⁸⁵Sr and⁵⁵Y has been investigated using NaI(Tl)-detectors. Spectroscopic-coincidence techniques have been employed to examine theK-electron capture rates. The experimental results areP _K ω _K (Sr)=.5959 ± 0.0035 andP _K ω _K (Y)=0.6340± 0.0032. Using theK-capture probabilities, derived from the capture ratios ofBrysk andRose with the exchange correction ofBahcall:P _K (Sr)=0.880± 0.008 andP _K (Y)=0.883 ± 0.008, one can derive from these results the fluorescence yieldsω _K (Rb)=0.677± 0.009 andω _K (Sr)=0.712± 0.010. Functions ofω _K (Z) were fitted to recent experimental data and tabulated forZ=5–90. In addition to these results the half life of the 514 keV state of⁸⁵Rb and the branching ratios and the positron rate of the⁸⁸Y-decay have been measured with the same techniques. The data obtained partly disagree from measurements of other authors.     

In beam gamma spectroscopy of62Zn

The decay scheme of⁶²Zn has been investigated by studying the yield functions, angular distributions and coincidence relation-ships of theγ-rays emitted in the⁶³Cu(p, 2nγ) and⁶⁰Ni(α, 2nγ) reactions. Spins up to7? were assigned to the observed states. Nuclear Reactions ⁶⁰Ni(α, 2nγ)⁶²Zn,E _α=28–35 MeV and⁶³Cu(p, 2nγ)⁶²Zn,E _p = 22–31 MeV; measuredE _γ,I _γ(θ),I _γ(E _p , andI _γ,E _α-γ coincidences,⁶²Zn deduced decay scheme. Enriched target, Ge(Li) detectors.     

States in86Sr,84Sr and87Y populated in the (p,t) reaction

The (p,t) reactions on⁸⁸Sr,⁸⁴Sr and⁸⁹Y have been carried out at a bombarding energy of 49.5 MeV. Some low-lying excitations in⁸⁶Sr and⁸⁴Sr associated with configurations of 1g _9/2 and 2p _1/2 neutrons have been identified. Levels populated to 4 MeV of excitation in the strontium nuclei and to 2.5 MeV in⁸⁷Y have been studied in the present experiment. In the case of⁸⁷Y most of the levels populated are of a complex nature.     

Fluoroform: The polyad at 8–9 μm

A high-resolution Fourier transform spectrum of CF₃H has been analyzed in the region of the interacting bands ν₂, ν₅, and ν₃ + ν₆. Several interactions were successively introduced in the model. In a first step, only the X-Y Coriolis interaction between ν₅ and ν₂, the Fermi term between ν₅ and ν₃ + ν₆ and the l(2, 2) resonance within ν₃ + ν₆ were used. Later the l(2, ?1) interaction within ν₅ and finally the accidental l(1, ?2) interaction between ν₂ and ν₅ were added. Finally, more than 2000 energy levels were fitted with a standard deviation of 0.5 × 10^?3 cm^?1.     

Decay of three-particle high spin states in85Y

High spin states in⁸⁵Y have been excited in the reaction⁷²Ge(¹⁶O,p2n) at 48–60 MeV beam energy. From measurements ofnγ andγγ coincidences, excitation functions and angular distributions, the high spin spectrum of⁸⁵Y has been established up to 5.4 MeV excitation energy and spinI≦29/2. Lifetimes or limits of lifetimes have been determined for 14 levels via the recoil distance and Doppler shift attenuation method. Theg _9/2 decoupled proton band is found to backbend atI ^π=17/2⁺ as also seen in the reduction of the 17/2⁺→13/2⁺ and 21/2⁺→17/2⁺ E2 transition strengths. The lowest (3qp) positive parity band has predominantly aν ² g _9/2×πg _9/2 structure. The observed negative parity yrast states in the spin range 15/2^?≦I≦29/2^? are most probably of (g _9/2)² ×(f _5/2,p _1/2) (3qp) nature as suggested by a comparison of the⁸⁴Sr and⁸⁵Y level structures and electromagnetic transition strengths.     

A simple modification of the maximal mixing scenario for three light neutrinos

We suggest a simple modification of the maximal mixing scenario (withS ₃ permutation symmetry) for three light neutrinos. Our neutrino mass matrix has smaller permutation symmetryS ₂(ν _μ ?ν _e ), and is consistent with all neutrino experiments except the³⁷Cl experiment. The resulting mass eigenvalues for three neutrinos arem ₁≈(2.55?1.27)×10^?3eV,m _2,3≈(0.71?1.43)eV for Δm _LSND ² =0.5?2.0eV². Then these light neutrinos can account for ～(2.4?4.8)% (6.2?12.4%) of the dark matter forh=0.8 (0.5). Our model predicts theν _μ →ν _τ oscillation probability in the range sensitive to the future experiments such as CHORUS and NOMAD.     

具有广义协变的包含重力场贡献的重力场方程

利用半度规λ^(α)_μ表象的数学工具定义一个对广义坐标具有协变形式的重力场矢势函数ω^(α)_μ≡-cλ^(α)_μ，给出一个具有广义协变的包含重力场贡献的重力场方程R_μν-g_μνR/2+Λg_μν=8πG(T^(Ⅰ)_μν+T^(Ⅱ)_μν) 关键词： 重力场方程 协变形式 能量-动量张量 量子化     

Energy spectra and energy correlations in the decayH→ZZ→μ+μ−μ+μ−

It is shown that in the sequential decay $H \to ZZ \to (f_1 \bar f_1 ) + (f_2 \bar f_2 )$ , the energy distribution of the final state particles provides a simple and powerful test of theHZZ vertex. For a standard Higgs boson, the energy spectrum of any final fermion, in the rest frame ofH, is predicted to be dΓ/dx～1+β⁴?2(x?1)², with $\beta = \sqrt {1 - 4m_Z^2 /m_H^2 } $ and 1?β≤x=4E/m _H ≤1+β. By contrast, the spectrum for a pseudoscalar Higgs is dΓ/dx～β²+(x?1)². There are characteristic energy correlations betweenf ₁ andf ₂ and betweenf ₁ andf ₂. These considerations are applied to the “gold-plated” reactionH→ZZ→μ⁺μ^?μ⁺μ^?, including possible effects ofCP-violation in theHZZ coupling. Our formalism also yields the energy spectra and correlations of leptons in the decay $H \to W^ + W^ - \to l^ + v_l l^ - \bar v_l $ .     

Investigation of neutron deficient nuclei in the region 28<N,Z <50 with the help of heavy ion compound reactions

In-beamγ ray spectroscopy withγ singles spectra,γγ coincidences andγ ray angular distributions has been performed with several target-projectile combinations:^natCa +³²S,^natCa +⁴⁰Ca,⁵⁴Fe +¹⁴N,⁵⁸Ni +¹²C,⁵⁸Ni +¹⁴N,⁶⁶Zn +¹⁶O,⁶⁸Zn +¹⁶O. Level schemes of⁶⁶Ge,⁶⁸Ge,⁶⁹As,⁷⁰Se,⁷⁴Kr,⁸⁰Sr and⁸²Sr have been deduced. The following level energies and spin-parity assignments have been found:⁶⁶Ge: 957.4 keV, 2⁺; 1693.7; 2174.7, (4⁺); 3685.7; 4207.5;⁶⁸Ge: 1015.8, 2⁺; 1777.9, 2⁺; 2267.9, 4⁺; 2428.8, 3(⁺); 2649.1, 3^?; 3582.3, (5^?); 3649.3, (5^?); 3696.2, (6⁺); 3883.3, (6^?); 4054.4, (7^?); 4454.6; 4837.3;⁶⁹As: 98.2; 164.6;789.6;863.2; 1306;2160;2210.4;2831.5;3258.3;3263.5;3991.1;5195.7;⁷⁰Se: 945.4, 2⁺; 1600.9; 2039.4, (4⁺);⁷⁴Kr: 455.7, 2⁺; 1013.5, (4⁺); 1781.5;⁸⁰Sr: 385.4, 2⁺; 980.2, (4⁺); 1763.2, (6⁺);⁸²Sr: 573.4, 2⁺; 1328.5,(4⁺); 2229.6,(6⁺). γ ray activity spectra have been measured after the bombardment of natural Ca with³²S. The half-life of the new isotope⁶⁹Se has been found to be 27±3 sec. Recoil distance Doppler-shift measurements have been performed with the reactions^62,64Ni,⁶⁶zn(¹⁶O, 2n)^{76, 78} Kr,⁸⁰Sr. The following half-lives have been determined:⁷⁶Kr: 423.8 keV, 2⁺, 37±5 psec; 1034.2,4⁺, 5.7±1.6;⁷⁸Kr: 455.3, 2⁺, 25±3; 1120.0, 4⁺, 3.8±1;⁸⁰Sr: 385.4, 2⁺, 44±6. The energy and half-life systematics of the first excited state of even-even nuclei suggest a maximum of nuclear deformation in the region 28≦N, Z≦50 near ₃₈ ⁷⁶ Sr₃₈ or ₄₀ ⁷⁸ Zr₃₈.     

Semiconducting TlSr2RCu2O7 (R=rare earth) and its superconducting derivatives

Semiconducting TlSr₂RCu₂O₇ (R=Pr or Er) with a 1212-type structure has been synthesized in the single-phase form. Partial substitution of Sr²⁺ for R³⁺ converts this semiconductor to a 90 K superconductor TlSr₂(R_1–y Sr _y )Cu₂O₇. A combination substitution, Sr²⁺ for R³⁺ and Pb⁴⁺ for Tl³⁺, leads to the Ca-free 100 K superconductor (Tl, Pb)Sr₂(R, Sr)Cu₂O₇. The results are explained in the framework of the mixed Cu²⁺/Cu³⁺ valence.     

Angular correlations for semileptonic D meson decays

We study the exclusive semileptonicD meson decaysD→K+π+l+ν. For this we develop the general formalism for the joint angular distribution of the charged lepton and theK meson and calculate the helicity dependent decay widths which determine the full angular distribution for several models withK ^*(892) andK ₀ ^* (1430) intermediate state with nonresonant background terms calculated from chiral Lagrangians.