Fragmentation of the high spin discrete neutron and proton states of209Pb and209Bi

The distribution of the discrete 1h _9/2, 2f _7/2, 1i _13/2 and 2f _5/2 proton states of²⁰⁹Bi and 2g _9/2, 1i _11/2, 1j _15/2 and 2g_7/2 neutron states of²⁰⁹Pb have been obtained within the particle-vibration coupling model calculation and compared with the experimental datas baising on the most recent high resolution stripping reaction on²⁰⁸Pb using 480 MeV¹²C projectile. The optimised shell model energies arising from the core-polarisation effect have profound influence for both the study of the structures of the high spin continuum shell model states of²⁰⁸Pb and stability of superheavy nuclei.     

Lifetime measurements of spherical and deformed states in 1f7/2 nuclei

Lifetimes have been determined using the Doppler Shift Attenuation Method in the N ≈ Z nuclei ⁴⁶V and ⁴⁸V, populated with the reaction ²⁸Si on ²⁴Mg at 115 MeV and ²⁴Mg on ²⁸Si at 100 MeV using Au and Pb backed targets. The coexistence of spherical and deformed states in the middle of the 1f_7/2 shell is discussed. The B(E2) and B(M1) reduced rates agree very well with large scale shell model predictions.     

Three-step laser excitation of the 6p3/2ns,nd, ng autoionizing Rydberg levels via the 6p5f 1/2[5/2]2 level of lead

Odd parity autoionizing Rydberg levels of atomic lead in the energy region above the 6p1/2 ionization threshold have been investigated using three-step laser excitation in conjunction with an atomic beam apparatus. The 6p3/2ns (J = 1, 2), 6p3/2nd (J = 1, 2, 3) and 6p3/2ng (J = 2, 3) levels have been observed from the 6p5f 1/2[5/2]2 intermediate level. Energy values and FWHM of forty levels belonging to the 6p3/2ns, 6p3/2nd and 6p3/2ng configurations are presented. Six levels based on the 6p3/2ng (5, 13 n 15) configurations and three levels attached to the 6p3/28d configuration are reported for the first time. The present study of the low-lying autoionizing levels attached to the 6p3/25g (J = 2, 3) configuration completes the series adjacent to the 6p1/2 limit.     

Fragmented 2d 5/2, 1g 7/2 and 1g 9/2 deep proton-hole states of207TI

The three proton-hole states ?2d_5/2, 1g_7/2 and 1g_9/2 are found to be fragmented as a result of coupling of these states with the 3^?, 5^?, 2⁺, 4⁺ and 6⁺ collective states of²⁰⁸Pb. The excited states in²⁰⁸Pb (t,α) reaction can be quantitatively explained in terms of altered 2d_5/2, 1g_7/2 and 1g_9/2 states with the hole-core coupling model.     

Core polarization and 5/2+ states in91Nb

The energies and spectroscopic factors ofJ ^π=5/2⁺ states of nucleus⁹¹Nb excited via a reaction transferring a proton to the 2d _5/2 orbit of⁹⁰Zr target state have been calculated. Effective two-body interaction used has been extracted from the experimentally observed two-body energies of (1g ₉ ^2/?1 (n) 2d _5/2(n)), (1g ₉ ^2/?1 (n) 1g _9/2(p)) and (1g _9/2(p)-2d _9/2(n)) multiplets in⁹⁰Zr,⁹⁰Nb and⁹²Nb nuclei respectively. Most of the calculated energies and the strengths ofJ ^π=5/2⁺ levels have reasonably good counterparts in the experimental spectrum, however the calculation shows about 17% strength lying at 6.8 MeV, without having a confirmed counterpart in the observed level scheme. The reduced transition strengthsB(M1) forM l transitions from 5/2^? T>(11/2) state to the various components of 5/2⁺ T<(=9/2) state have also been reported; but the corresponding experimental values are not available. The main feature of the reduced transition strengths is that theM1 transition to the state at 3.69 MeV is inhibited whereas that to the state at 6.79 MeV is enhanced, the relevant core-configuration, interfering destructively in the former case and constructively in the latter.     

Luminescence properties of K1/2Bi1/2TiO3:Pr3+ and Na1/2Bi1/2TiO3:Pr3+

The luminescence properties of K(1/2)Bi(1/2)TiO(3):Pr(3+) and Na(1/2)Bi(1/2)TiO(3):Pr(3+) powders are investigated in the temperature range 10-600 K. The experimental data are interpreted on the basis of metal-to-metal charge transfer processes and by considering Bi(3+)-to-Pr(3+) sensitization effects.     

Effect of excess Bi2O3 on the electrical properties and microstructure of (Bi1/2Na1/2)TiO3 ceramics

(Bi_1/2Na_1/2)TiO₃ ceramics (BNT) with 0–6 mol% of excess Bi₂O₃ are prepared by conventional solid-state sintering. The electrical properties of the samples are examined. The addition of excess Bi₂O₃ reduces the leakage current of BNT ceramics significantly, thus facilitating the poling process, and improves their piezoelectric properties slightly for certain amounts of added Bi₂O₃. BNT ceramics have very high dielectric constants and dissipation factors at low frequency and high temperature due to their high conductivity. Adding excess Bi₂O₃ to BNT ceramics affects their dielectric behavior and phase transition temperatures. Grain growth is suppressed by adding Bi₂O₃ and no second phase is observed for BNT ceramics with up to 6 mol% of excess Bi₂O₃ added.     

Magnetic Properties of Sb2S3 and Bi2S3 as Evidenced by 121,123Sb and 209Bi NQR Spectra

Journal of Experimental and Theoretical Physics -     

Inelastic cross-sections and natural lifetimes for the 62D3/2, 5/2 and 82S1/2 states of Rb

The results of an experimental study of population dynamics following excitation of [0pt] and [0pt] states of rubidium are reported. Excitation transfer and quenching cross-sections in collisions with ground state rubidium atoms, and natural lifetimes have been measured. The experiment was performed in a vapour cell, using pulsed two-photon excitation and photon counting detection. The analysis of time dependent signals was based on a rate equation model in which transitions induced by thermal radiation have been accounted for. The measurements yielded following results: (1) [0pt] state J-mixing cross-section: [0pt] ; (2) cross-sections for [0pt] excitation transfer process: [0pt] ; (3) quenching cross-sections: [0pt] , [0pt] , [0pt] ; [0pt](4) radiative lifetimes: [0pt] ns, [0pt] ns, [0pt] ns. Received 1st December 1998 and Received in final form 17 May 1999     

Thermoelectric properties of Bi2Se3/Bi2Te3/Bi2Se3 and Sb2Te3/Bi2Te3/Sb2Te3 quantum well systems

In this work, we develop a theory of thermoelectric transport properties in two-dimensional semiconducting quantum well structures. Calculations are performed for n-type 0.1 wt.% CuBr-doped Bi₂Se₃/Bi₂Te₃/Bi₂Se₃ and p-type 3 wt.% Te-doped Sb₂Te₃/Bi₂Te₃/Sb₂Te₃ quantum well systems in the temperature range 50–600 K. It is found that reducing the well thickness has a pronounced effect on enhancing the thermoelectric figure of merit (ZT). For the n-type Bi₂Se₃/Bi₂Te₃/Bi₂Se₃ with 7 nm well width, the maximum value of ZT is estimated to be 0.97 at 350 K and for the p-type Sb₂Te₃/Bi₂Te₃/Sb₂Te₃ with well width 10 nm the highest value of the ZT is found to be 1.945 at 440 K. An explanation is provided for the resulting higher ZT value of the p-type system compared to the n-type system.     

Eu原子4f~76p_(3/2)6d自电离过程的动力学特性

采用孤立实激发技术(isolated-core excitation, ICE)及速度影像技术(velocity-map imaging,VMI),研究了Eu原子4f~76p_(3/2)6d自电离过程的动力学特性.孤立实激发技术用于将Eu原子从基态4f~76s~(2 8)S_(7/2)经中间态4f~76s6p激发到4f~76s6d里德堡态,然后将其进一步激发至4f~76p_(3/2)6d自电离态;速度影像技术用于探测其自电离过程的动力学特性,从而获得自电离衰变的分支比(branch ratio, BR)和弹射电子的角分布(angular distribution, AD).自电离衰变的分支比代表离子的能量分布,从中获得VMI影像的径向信息;而通过各向异性参数描述的弹射电子的角分布揭示了VMI影像的角向信息.此外,讨论了自电离衰变分支比和弹射电子角分布在整个自电离共振能域内的变化情况.基于4f~76s~+和4f~75d~+两个离子态的分支比,讨论了实现Eu离子粒子数反转的可能性.     

Masses of nuclei of the 1f 7/2 subshell

Binding and one-nucleon separation energies are calculated for nuclei with 20 ≤ Z, N ≤ 28, where both protons and neutrons occupy the 1f _7/2 valence subshells. To this aim, two different methods are applied. The first method employs the self-consistent approach with the effective Skyrme forces and pairing interaction, while the second one makes use of the semiempicial multiparticle shell model with the effective two-body matrix elements of the interaction defined from the empirical data. The intercomparison between the two methods is carried out. The text was submitted by the authors in English.     

Bi,Sn and Sb valence states in highT c (Bi,Pb/Sn,Sb)2Sr2Ca2Cu3Oy

The valence of Bi and its substituents Sn and Sb are investigated in the high temperature superconductor (Bi_0.8X_0.15Sb_0.05)₂Sr₂Ca₂Cu₃O_y (often denoted 2223) where X=Pb or Sn. Pb and Sn are isoelectronic with the valence states 2+ and 4+; Bi and Sb are as well with valence states 3+ and 5+. The valence state of Sn and Sb has been obtained from Mössbauer spectroscopy: they exist in the high charge states 4+ and 5+ respectively. Sn, Sb, and presumably Pb, take on the high valence state, and so furnish electrons to the conduction band. This is probably the reason why, although the (Pb, Sb)-doping aids in stabilizing the 2223 crystal structure, it is detremental to the electronic properties which lead to the superconducting phase. The valence state of Bi has been studied using X-ray photoelectron spectroscopy (XPS). These results show clearly that the Bi-based superconductor has a metal-like density of states at the Fermi level, and that the valence in the (Pb, Sb)-doped compounds is less than 3. This very surprising change in valence will have a profound effect on the superconducting properties, and is probably associated with the high valent states of Pb, Sn and Sb.     

Polarizabilities of rubidium (9-10)S 1/2 and 8D 3/2, 5/2 states

Polarizabilities of several rubidium states were determined by measuring stark shifts of transitions using an electro-optically modulated laser beam to excite an atomic beam. The voltage required for atoms excited by the laser beam in an electric field to be simultaneously in resonance as atoms excited by a frequency sideband of the laser in a field free region was measured. The scalar α and tensor α ₂ polarizabilities were found to be: α (9 S _1/2 ) = 103.77±0.09, α (10 S _1/2 ) = 272.54±0.16, α (8 D _3/2 ) = 230.68±0.25 and α ₂ (8 D _3/2 ) = 26.55±0.10, α (8 D _5/2 ) = 222.68±0.14 and α ₂ (8 D _5/2 ) = 51.91±0.10 MHz/(kV/cm)². The results are 100 times more accurate than previous measurements and are within 1% of those found theoretically using a Coulomb approximation calculation. Received 7 September 2000 and Received in final form 6 December 2000