Level densities for nuclei with 47 ≤ A ≤ 59

Nuclear level densities of ⁴⁷V, ⁴⁸V, ⁴⁹V, ⁵³Mn, ⁵⁴Mn, ⁵⁷Co, ⁵⁹Ni and their energy dependences are determined from measurements of the neutron evaporation spectra in the (p, n) reaction. Neutron spectra from the (p, n) reaction on nuclei of ⁴⁷Ti, ⁴⁸Ti, ⁴⁹Ti, ⁵³Cr, ⁵⁴Cr, ⁵⁷Fe, and ⁵⁹Co are measured at proton energies between 7 and 11 MeV. The data are analyzed in terms of statistical equilibrium and pre-equilibrium models of nuclear reactions.     

恢复系数e一定满足0≤e≤1吗？

作者从恢复系数e的一般定义出发，引入了“穿透”碰撞与“爆炸”碰撞的概念，从而将e的取值范围扩大到实数。     

Nan(5≤n≤10)小团簇相变

采用紧束缚的分子动力学模型,对Nan(5≤n≤10)小团簇的键长涨落、势能、热容量等熔化性质在50 K～1500 K温区进行了模拟研究,结果表明:它们发生两次相变,一种在230 K～300 K的温度范围内,依次有块体玻璃态转变;一种在550 K～870 K温度段,依次经历了熔化相变.同时也得到随着团簇体系的减小,势能由下向上排列的曲线,即体系的势能由低变高.     

恢复系数e一定满足0≤e≤1吗?

作者从恢复系数ｅ的一般定义出发，引入了“穿透”碰撞与“爆炸”碰撞的概念，从而将ｅ的取值范围扩大到实数．     

An angle-dependent potential and alpha-decay half-lives ofdeformed nuclei for 67≤Z≤91

The half-lives of deformed nuclei are reported for 67≤Z≤91. We consider an angle-dependent potential which yields multiple approximations. The results are in better agreement with the experimental data when the multiple approximation is solely considered for the daughter nuclei.     

Luminescence properties of Sr3−x−3y/2MxCeyAlO4F (M=Ca,Ba, 0≤x≤0.9, 0.001≤y≤0.05) phosphors

Luminescent materials composed of Sr_3?x?3y/2M_xCe_yAlO₄F (M=Ca, Ba, 0≤x≤0.9, 0.001≤y≤0.05) were prepared by the solid-state reaction method. X-ray diffraction (XRD) patterns of the obtained oxyfluorides are exhibited for indexing peak positions. Dynamic excitation and emission spectra of the Ce³⁺-activated oxyfluoride phosphors are clearly monitored. The critical emission quenching as a function of Ce³⁺ contents in Sr_2.5?3y/2M_0.5Ce_yAlO₄F phosphors is revealed at quite low concentrations of the activator. CIE coordinates of blue and green Sr_2.5?3y/2M_0.5Ce_yAlO₄F phosphors are clearly measured. The relative quantum efficiency of Sr_2.4985Ca_0.5Ce_0.005AlO₄F based on the integrated emission is determined. The Sr_3?x?3y/2M_xCe_yAlO₄F phosphors excited near 410 nm light could be prominent phosphors in applications of NUV-LED.     

25≤Z≤35类氟离子能级和相干辐射波长的MCDF计算

本文用相对论多组态Dirac-Fock广义平均能级(MCDF-EAL)模型,计算了可形成软x射线区相干辐射的可能的类氟等离子体型激光工作物质:25≤Z≤35的类氟离子2s~22p~5、2s~22p~43l、2s2p~53l、2p~63l组态共113条能级,以及上述单激发态M亚壳层至2s~22p~5态的~2P_(3/2)、~2P_(1/2)和2s2p~6态的~2S_(1/2)能级全部允许跃迁的强相干辐射波长值。从上述的波长理论计算值与实验观测值对比,可知我们的计算结果是相当可靠的。     

51≤Z≤55类镍离子4s-4p跃迁的理论计算

用多组态自洽场理论结合最小二乘拟合方法,对51≤Z≤55类镍离子 3d94s,3d94p组态的能级进行计算,根据能级值算出4s-4p跃迁的谱线波长,并 给出各谱线的HFR振子强度。     

Pr1—xKxMnO3（0.0≤x≤0.15）的化学键性质研究

采用半经验的复杂晶体化学键理论研究了ｒ１－ｘＫｘＭｎＯ３的化学键性质。计算结果表明，Ｐｒ－Ｏ键及Ｋ－Ｏ的共价性随钾掺杂浓度的增加而略有减小，Ｍｎ－Ｏ的共价性则增加，且Ｍｎ－Ｏ的共价性要强于Ｐｒ（Ｋ）－Ｏ键，得到的键极化率也服从同样的规律。     

Pion form factor in the range −10 GeV2 ≤ s ≤ 1 GeV2

Based on the field-theory-inspired approach, a new expression for the pion form factor F _π is proposed. It takes into account the pseudoscalar meson loops π⁺π^? and $K\bar K$ and the mixing of ρ(770) with heavier ρ(1450) and ρ(1700) resonances. The expression ensures correct analytical properties and describes the data in the wide range of the energy squared ?10 GeV² ≤ s ≤ 1 GeV² without introducing the phenomenological Blatt-Weisskopf range parameter R _π.     

An angle-dependent potential and alpha-decay half-lives ofdeformed nuclei for 67≤Z≤91

The half-lives of deformed nuclei are reported for 67≤Z≤91. We consider an angle-dependent potential which yields multiple approximations. The results are in better agreement with the experimental data when the multiple approximation is solely considered for the daughter nuclei.     

Atomic structure of Pdn (4 ≤ n ≤ 15) nanoclusters

The results of molecular dynamics simulation of the process of atom-by-atom growth of palladium nanoparticles are presented. The structures obtained for the Pd _n clusters agree well with the results of the first-principles calculations. The low-symmetry atomic configurations for the structure of the Pd₄ and Pd₁₃ clusters have been obtained using the semiempirical potentials of the interatomic interaction for the first time.     

Half-Lives for Alpha Radioactivity of Elements with 104 ≤ Z ≤ 120 within Unified Fission Model

α decay half-lives are calculated using the Qα values obtained by Semi-empirical Shell Model in the framework of the Unified Fission Model (UFM) with the Coulomb repulsion, nuclear attraction due to proximity potential, and rotational energy due to angular momentum transfer of α particle. In addition, the calculated and experimental half-lives of 425 nuclei are compared to check the validity of the model applied on α decay. The calculated half-lives of α decay are in good agreement with the experimental data. Finally, some usefulpredications on the α decay half-lives are provided for future experiments.     

La0.67-xSmxSr0.33MnO3(0.40≤x≤0.60)体系的TCR研究

通过测量La0.67-xSmxSr0.33MnO3(x=0.40,0.50,0.60)体系的M～T曲线和ρ～T曲线,研究了La位Sm掺杂对体系电阻温度系数 (TCR)的影响.实验结果表明:Sm掺杂引起的电阻率曲线急剧变化,导致大的TCR出现;TCR在x=0.40时出现峰值,随Sm掺杂的增加,TCR值逐渐减小.体系出现大的TCR,来源于Sm掺杂引起的晶格畸变和额外磁性.     

Transport properties of the single-crystal La2−xBaxCuO4 (0≤x≤0.11)

We report on the temperature dependence of the in-plane electrical resistivity ρ_ab and the in-plane Hall coefficient R_H in various magnetic fields of the single-crystal La_2−xBa_xCuO₄ with x=0.083 and 0.11. In x=0.11, which is close to x=1/8, where the superconductivity is strongly suppressed, a clear jump in ρ_ab and a drop in R_H have been observed at T_d2∼53 K, where the structural phase transition between the orthorhombic mid-temperature and tetragonal low-temperature phases occurs. Moreover, a sign reversal of R_H has been observed below ∼25 K and the magnitude of the sign reversal increases with increasing magnetic field. In x=0.083, on the other hand, there is neither jump in ρ_ab nor drop in R_H at T_d2, and also no sign reversal in R_H at low temperatures even in magnetic fields up to 9 T. In conclusion, there is no doubt that a static stripe order of holes and spins, observed in La_1.6−xNd_0.4Sr_xCuO₄ with x∼1/8, is formed below T_d2 also in La_2−xBa_xCuO₄ with x∼1/8. The R_H in the stripe-ordered state has a negative value, which is consistent with the recent theory by Prelovšek et al.     

La2—xBaxCuO4（0≤x≤0.22）的低温结构不稳定性研究

测量了Ｌａ２－ｘＢａｘＣｕＯ４单相多晶材料在１０Ｋ－３００Ｋ的纵波超声声速和超 声衰减，在高温四方相向低温正交相结合相变温度附近，发现强烈的晶格软化现象并伴有明显的超声内耗峰，温度低于６０Ｋ在所有样品中均发现明显的超声异常现象，这表明在ｘ＝０到ｘ＝０范围内Ｌａ２－ｘＢａｘＣｕＯ４中都可能存在不稳定的低温结构相变。ｘ＝０，０．１２和０．２２几个样品的超声衰减在低温下明显高于其它超志性能好的样品，这可     

High-field magnetostriction in CeNiSn1−xGex (0≤x≤1) strongly correlated systems

Magnetization (down to 1.8 K and up to 9 T) and magnetostriction (down to 4.2 K and up to 30 T) measurements have been performed in the series of polycrystalline intermetallics CeNiSn_1?xGe_x (0≤x≤1), which show a crossover from Kondo-lattice to fluctuating valence behaviors with x increase. Magnetostriction observed can be denominated as “colossal” for a paramagnet (up to 0.68% at 150 K and 30 T), with no sign of saturation. Field, H, induced metamagnetic transitions associated to a change in Ce valence are observed. Three kinds of analysis of magnetostriction have been performed to ascertain the magnetostriction origin. At relatively low field and low temperatures these systems follow well the standard theory of magnetostriction (STM), revealing single-ion crystal field and exchange origins, and a determination of the α-symmetry microscopic magnetoelastic parameters have been performed. The valence transition is well explained in terms of the interconfigurational model, which needs an extension up to power H⁴. Application of the scaling (thermodynamics corresponding low states) allows the obtainment of the Grüneisen constant, which increases with x. Needed elastic constants measurements are also reported.     

Helimagnetism of CuxZn1−xCr2Se4 (for 0.0 ≤ × ≤ 0.1)

Abstract

The magnetization, the susceptibility and the magnetic anisotropy field of Cu _x Zn_1?xCr₂Se₄ compounds have been studied at low temperatures (down to 2.9 K) in: high magnetic stationary fields (up to 14 T), high pulsed magnetic fields (up to 25 T), medium magnetic stationary fields (up to 0.6 T). The magnetic structure of these spinels was studied by neutron powder diffraction.

The magnetic properties of Cu_xZn_1?xCr₂Se₄ are explained in terms of the molecular field approximation assuming the existence of 90° exchange interactions, ferromagnetic for Cr-Se-Cr between the nearest Cr ions and antiferromagnetic for Cr-Se-Se-Cr between the second-nearest Cr ions. The exchange parameters and integrals for the whole series under consideration are calculated. Taking into account the three magnetic phase transitions observed in these spinels (Juszczyk, Krok, Okońska-Koz?owska, Broda, Warczewski, Byszewski, 1981) and the neutron diffraction studies a modification of the simple spin spiral forced by a strong magnetic field is described.