Superdeformed structures and low Ω parity doublet in Ne-S nuclei near neutron drip-line

The structures of Ne, Na, Mg, Al, Si, P and S nuclei near the neutron drip-line region are investigated in the frame-work of relativistic mean field theory and non-relativistic Skyrme Hartree-Fock formalism. The recently discovered nuclei ⁴⁰Mg and ⁴²Al, which are beyond the drip-line predicted by various mass formulae are located within these models. We find many largely deformed neutron-rich nuclei, whose structures are analyzed. From the structure anatomy, we find that at large deformation low orbits of opposite parities (e.g. $\frac{1} {2}^ +$ and $\frac{1} {2}^ -$ ) occur close to each other in energy.     

Determination of the structure of {31}ne by a fully microscopic framework

We perform the first quantitative analysis of the reaction cross sections of {28-32}Ne by {12}C at 240 MeV/nucleon, using the double-folding model with the Melbourne g matrix and the deformed projectile density calculated by antisymmetrized molecular dynamics. To describe the tail of the last neutron of {31}Ne, we adopt the resonating group method combined with antisymmetrized molecular dynamics. The theoretical prediction excellently reproduces the measured cross sections of {28-32}Ne with no adjustable parameters. The ground state properties of {31}Ne, i.e., strong deformation and a halo structure with spin parity 3/2{-}, are clarified.     

The liquid-lithium target at the soreq applied research accelerator facility

The European Physical Journal A - In stars, the fusion of $$^{22}$$ Ne and $$^4$$ He may produce either $$^{25}$$ Mg, with the emission of a neutron, or $$^{26}$$ Mg and a $$\gamma $$ ray. At high...     

丰中子A~100质量区内的扁椭球高K同核异能态

远离核素图上“稳定谷”的丰中子核一直是核物理学研究的热点。作为形变丰中子核的一种特殊的亚稳定激发态,高K同核异能态的形状大多数为长椭球,扁椭球的高K同核异能态非常少见。近期的一项实验认为丰中子核94Se上的$ {K}^{\mathrm{\pi }}={7}^{-} $两准粒子态为扁椭球。这是形变原子核上存在扁椭球高K同核异能态的第一个实验证据。结合相关实验,我们猜测可能有其它尚未发现的扁椭球高K同核异能态存在于丰中子A~100质量区。利用组态限制势能面计算方法,本文对丰中子A~100质量区内的$ {K}^{\mathrm{\pi }}={9}^{-} $和$ {K}^{\mathrm{\pi }}={7}^{-} $两准粒子态进行了研究,并预言了此质量区内扁椭球高K同核异能态的可能位置。根据Nilsson模型,扁椭球高K同核异能态的存在与费米能级附近的高Ω单粒子轨道有关。这些高Ω单粒子轨道来源于高j闯入态在扁椭球形变时的退简并。扁椭球高K同核异能态是研究丰中子核形变参数、激发能等物理性质的理想对象,有助于加深我们对于形变原子核能级结构的理解。     

Optical parameters and energy levels splitting of Ho^3＋ in Ho^3＋： GdVO4

Ho^3＋ ： GdVO4 is a new laser material suitable for high-power laser systems. In this paper we measure the absorption spectra of Ho^3＋ in the sample Ho^3＋： GdVO4. The intensity parameters are calculated by using the Judd-Ofelt theory. Some predicted spectroscopic parameters, such as the spontaneous radiative transition rate, branching ratio and integrated emission cross section are dealt with. And we also compare the optical parameters with those of other materials. From these results, it is found that there are many transitions which have large oscillator strengths and large integrated emission cross sections. Especially the transitions such as ^5 F4 → ^5 I 8, ^5 S2→^5 I8, ^5 F5 → ^5 I8 and ^5 I7 →^ 5 I8 are useful in solid-state lasers and other fields. Finally, we discuss the splitting of the energy levels of Ho^3＋ in the crystal GdVO4 based on the group theory.     

Dy2 AlFe13 Mn3 化合物的本征磁致伸缩

通过X-射线衍射及磁测量手段研究了Dy2AlFe13Mn3化合物的结构及磁性质。研究结果表明Dy2AlFe13Mn3化合物具有六角相的Th2Ni17型结构。通过X-射线热膨胀测定法发现Dy2AlFe13Mn3化合物在245到344K的温度范围内存在负热膨胀现象，其平均热膨胀系数为α＝-1.1×10-4K-1K-1。在105到360K的温度范围内，通过比较磁性状态下的晶胞参数和由高温顺磁状态外延得到的低温顺磁状态下的晶胞参数间的差别计算了Dy2AlFe13Mn3化合物的本征磁致伸缩。结果表明Dy2AlFe13Mn3化合物的本征体磁致伸缩ωS在105到245K的温度范围内随着温度的升高而增大，由105K时的7.0×10-3 增加到245K时的9.1×10-3。随着温度的进一步升高，ωS反而减小。沿c轴方向的本征线磁致伸缩λc随着温度的升高而减小。基面内的本征线磁致伸缩λa在105到270K的温度范围内随着温度的升高而增大，从105K时的0.8×10-3增大到270K时的3.4×10-3，然后随着温度的进一步升高而减小。     

Improved analysis of the rare decay processes of Λ_b

It is noted that in the new Particle Data Group(PDG) version the rare decays of the Λ_b baryon have been revised with more accuracy. The new results show that most of the existing theoretical results on the process Λ_b→Λ_γ Lgbare larger than those of experiments. With the improved higher-order light-cone distribution amplitudes of the Λ baryon, we reanalyze the process in the framework of light-cone quantum chromodynamics sum rules and the branching ratio is estimated to be Br (Λ_b→Λ_γ)=(7.38_(-0.39)~(+0.40))×10~(16), which is consistent with the new experimental result. Furthermore, another process Λ_b→Λl~+l~- is also analyzed in the same frame. The final branching ratio is calculated to be Br (Λ_b→Λl~+l~-)=1.20×10~(-6), which is in good accordance with the data from the PDG and other theoretical predictions.     

Theoretical determination of electron binding energy spectra of anionic magnesium clusters

A recently developed accurate scheme for converting the single-particle eigenenergies of the density functional theory into electron binding energies is used to compute the spectra of electron binding energies in and . The computations are performed for different isomeric forms of the clusters using both pseudopotential and all-electron treatments. The results are compared with the data derived from electron photodetachment experiments, and the role of the different isomers in the interpretation of these data is examined.     

Low-Pressure Barrier Discharge Spectroscopy. Afterglow with Ne $$_{2}^{ + }$$ , Ne+, and Ne2+ Ions

Optics and Spectroscopy - The radiation of decaying plasma formed by electron–ion recombination processes involving three neon ions: the molecular ion Ne $$_{2}^{ + }$$ and the atomic ions...     

Study of semileptonic decay of ${\bar{B}}_{s}^{0} \rightarrow \phi {l}^{+}{l}^{-}$ in QCD sum rule

In this work we study the semileptonic decay of ${\bar{B}}_{s}^{0}\to \phi {l}^{+}{l}^{-}$ (l=e, μ, τ) with the QCD sum rule method. We calculate the ${\bar{B}}_{s}^{0}\to \phi $ translation form factors relevant to this semileptonic decay, then the branching ratios of ${\bar{B}}_{s}^{0}\to \phi {l}^{+}{l}^{-}$ (l=e, μ, τ) decays are calculated with the form factors obtained here. Our result for the branching ratio of ${\bar{B}}_{s}^{0}\to \phi {\mu }^{+}{\mu }^{-}$ agree very well with the recent experimental data. For the unmeasured decay modes such as ${\bar{B}}_{s}^{0}\to \phi {e}^{+}{e}^{-}$ and ${\bar{B}}_{s}^{0}\to \phi {\tau }^{+}{\tau }^{-}$, we give theoretical predictions.     

Impurity effects of the Λhyperon in the hypernuclear systems ${}_{{\rm{\Lambda }}}^{25}\mathrm{Mg}$ and ${}_{{\rm{\Lambda }}}^{29}\mathrm{Si}$

Based on the beyond-mean-field Skyrme–Hartree–Fock model, impurity effects of the Λhyperon in the hypernuclear systems ${}_{\,{\rm{\Lambda }}}^{25}$ Mg and ${}_{\,{\rm{\Lambda }}}^{29}$ Si are investigated, respectively. Four cases, in which the Λhyperon occupies the single-particle orbitals ${\rm{\Lambda }}$[000]${\tfrac{1}{2}}^{+}$, ${\rm{\Lambda }}$[110]${\tfrac{1}{2}}^{-}$, ${\rm{\Lambda }}$[101]${\tfrac{3}{2}}^{-}$ and ${\rm{\Lambda }}$[101]${\tfrac{1}{2}}^{-}$, are focused. In each case, the potential energy surface and the energy curves projected on certain angular momenta are employed to show the influence of the Λhyperon on the nuclear core. Beside the shrinkage effect that is induced by the Λhyperon occupying the s_Λ orbital, it is found that the Λhyperon on the p_Λ orbital, ${\rm{\Lambda }}$[110]${\tfrac{1}{2}}^{-}$, drives the nuclear core toward a prolate shape, while the ones on the other two p_Λ orbitals, ${\rm{\Lambda }}$[101]${\tfrac{3}{2}}^{-}$ and ${\rm{\Lambda }}$[101]${\tfrac{1}{2}}^{-}$, drive the nuclear core toward an oblate shape. The energy spectra and the corresponding intra-band E2 transition rates for the rotational bands are given as a prediction for future experiments.     

Systematic Approach to Calculate the Total Kinetic Energy Distribution of Actinides for the Photofission Phenomenon

Physics of Atomic Nuclei - The total kinetic energy as a function of fragment mass (TKE/A) was calculated for photofission of $${}^{232}$$ Th, $${}^{234}$$ U, $${}^{238}$$ U, $${}^{240}$$ Pu, and...     

Theoretical study on the transition properties of AlF

Potential energy curves of the X$^{1}\Sigma ^{+}$ and A$^{1}\Pi $ states of the AlF molecule are studied through the combination of the multi-reference configuration interaction (MRCI) approach and Davidson corrections (MRCI$+$Q). The AWCV5Z basis set is employed in the calculations. The transition dipole moments (TDMs) of the A$^{1}\Pi \leftrightarrow {\rm X}^{1}\Sigma^{+}$ transition are explored based on the AWCV5Z basis set and (4, 2, 2, 0) active space. The Schrödinger equation is solved via the LEVEL 8.2 program, and the vibrational levels and rotational constants of the X$^{1}\Sigma^{+}$ and A$^{1}\Pi $ states are calculated. It is shown that the AlF molecule has high diagonal Franck-Condon factors ($f_{00}=0.9949$ and $f_{11}=0.9854$) and large Einstein coefficients for the transition of A$^{1}\Pi {(\nu }'=0)\leftrightarrow {\rm X}^{1}\Sigma^{+}{\rm (\nu }'=0)$. In addition, the radiative lifetimes of the vibrational levels are close to 10$^{-9}$ s for the A$^{1}\Pi $ state. The line intensities of the A$^{1}\Pi {\rm (\nu }'=4-15)\leftrightarrow {\rm X}^{1}\Sigma^{+}{\rm (\nu }'=0)$ transitions are also calculated. The calculated TDMs and transition probabilities in this work are credible and provide some guidance for the study of similar transitions, particularly for exploring interstellar space.     

Judd-Oflet analysis of spectrum and laser performance of Ho：YAP crystal end-pumped by 1.91μm Tm：YLF laser

The Ho:YAP crystal is grown by the Czochralski technique.The room temperature polarized absorption spectra of Ho:YAP crystal was measured on a c cut sample with 1 at% holmium.According to the obtained Judd-Ofelt intensity parameters Ω2 = 1.42 × 10-20 cm2,Ω4 = 2.92 × 10-20 cm2,and Ω6 = 1.71 × 10-20 cm2,this paper calculated the fluorescence lifetime to be 6 ms for 5I7 →5 I8 transition,and the integrated emission cross section to be 2.24×10-18 cm2.It investigates the room temperature Ho:YAP laser end pumped by a 1.91 μm Tm:YLF laser.The maximum output power was 4.1 W when the incident 1.91 μm pump power was 14.4 W.The slope efficiency is 40.8%,corresponding to an optical to optical conversion efficiency of 28.4%.The Ho:YAP output wavelength was centred at 2118 nm with full width at half maximum of about 0.8 nm.     

Spectroscopy of 40Ca and negative-parity bands

We have studied the reactions as well as the binary channel , in order to search for deformed states, which form rotational bands in ⁴⁰Ca. We observe positive- and negative-parity bands. The negative-parity band is proposed to be a partner of an inversion doublet with the positive-parity states being based on 4p-4h configurations. The properties of the positive-parity states are discussed on the basis of the shell model and the parity doublet on the basis of a cluster model with intrinsic reflection asymmetric shapes.Received: 2 May 2003, Revised: 23 September 2003, Published online: 20 January 2004PACS: 21.10.-k Properties of nuclei; nuclear energy levels - 21.60.Gx Cluster models     

Investigation of transport properties of perovskite single crystals by pulsed and DC bias transient current technique

Time-of-flight (ToF) transient current method is an important technique to study the transport characteristics of semiconductors. Here, both the direct current (DC) and pulsed bias ToF transient current method are employed to investigate the transport properties and electric field distribution inside the MAPbI$_{3}$ single crystal detector. Owing to the almost homogeneous electric field built inside the detector during pulsed bias ToF measurement, the free hole mobility can be directly calculated to be about 22 cm$^{2}\cdot$V$^{-1}\cdot$s$^{-1}$, and the hole lifetime is around 6.5 μs-17.5 μs. Hence, the mobility-lifetime product can be derived to be $1.4\times 10^{-4}$ cm$^{2}\cdot$V$^{-1}$-$3.9\times 10^{-4}$ cm$^{2}\cdot$V$^{-1}$. The transit time measured under the DC bias deviates with increasing voltage compared with that under the pulsed bias, which arises mainly from the inhomogeneous electric field distribution inside the perovskite. The positive space charge density can then be deduced to increase from 3.1$\times10^{10}$ cm$^{-3}$ to 6.89$\times 10^{10}$ cm$^{-3}$ in a bias range of 50 V-150 V. The ToF measurement can provide us with a facile way to accurately measure the transport properties of the perovskite single crystals, and is also helpful in obtaining a rough picture of the internal electric field distribution.     

Singularities and accumulation of singularities of πN scattering amplitudes

It is demonstrated that for the isospin I = 1/2 πN scattering amplitude, T^I=1/2(s, t), $s={\left({m}_{N}^{2}-{m}_{\pi }^{2}\right)}^{2}/{m}_{N}^{2}$ and $s={m}_{N}^{2}+2{m}_{\pi }^{2}$ are two accumulation points of poles on the second sheet of complex s plane, and are hence accumulation of singularities of T^I=1/2(s, t). For T^I=3/2(s, t), $s={\left({m}_{N}^{2}-{m}_{\pi }^{2}\right)}^{2}/{m}_{N}^{2}$ is the accumulation point of poles on the second sheet of the complex s plane. The proof is valid up to all orders of chiral expansions.     

The splitting of low-lying states for hydroxyl molecule under spin--orbit coupling

The splitting of potential energy curves for the states $X^{2}\Pi _{3/2}$, $^{2}\Pi _{1/2}$ and $A^{2}\Sigma ^{ +}$ of hydroxyl OH under spin--orbit coupling (SOC) has been calculated by using the SO multi-configuration quasi-degenerate perturbation theory (SO-MCQDPT). Their Murrell--Sorbie (M--S) potential functions have been derived, then, the spectroscopic constants for $X^{2}\Pi _{3/2}$,$^{ 2}\Pi _{1/2}$ and $A^{2}\Sigma ^{ + }$ have been derived from the M--S function. The calculated dissociation energies for the three states are $D_{0}$[OH($X^{2}\Pi _{3/2})$]=34966.632cm$^{-1}$, $D_{0}$[OH($^{2}\Pi _{1/2})$]=34922.802cm$^{-1}$, and $D_{0}$[OH($A^{2}\Sigma ^{ + })$]=17469.794cm$^{-1}$, respectively. The vertical excitation energy $\nu [ {{ }^2\Pi _{1/2} ( {\nu = 0} ) \to {X}{ }^2\Pi _{3/2} ( {\nu = 0} )} ] = 139.6{\rm cm}^{-{\rm 1}}$. All the spectroscopic data for the $X^{2}\Pi _{3/2}$ and $^{2}\Pi _{1/2 }$ are given for the first time except the dissociation energy of $X^{2}\Pi _{3/2}$.     

Electron tunnelling phase time and dwell time through an associated delta potential barrier

The electron tunnelling phase time τP and dwell time τD through an associated delta potential barrier U(x) = ξδ(x) are calculated and both are in the order of 10^-17～10^-16s. The results show that the dependence of the phase time on the delta barrier parameter ξ can be described by the characteristic length lc = h^2/meξ and the characteristic energy Ec=meξ^2/h^2 of the delta barrier, where me is the electron mass, lc and Ec are assumed to be the effective width and height of the delta barrier with lcEc=ξ, respectively. It is found that TD reaches its maximum and τD = τp as the energy of the tunnelling electron is equal to Ec/2, i.e. as lc =λDB, λDB is de Broglie wave length of the electron.     

A unified description of shape coexistence and mixed-symmetry states in ~(98)Mo using IBM-2

Level structure and electromagnetic transitions in ~(98)Mo have been investigated on the basis of the proton-neutron interacting boson model(IBM-2) by considering the energy difference between neutron boson ε_ν and proton boson ε_π. The results are compared with the recent experimental data and it is observed that they are in good agreement. In particular, the strongest M1 transition from 2_5~+ state to 2_2~+ can be well reproduced, from which one can determine the 2_5~+ as an mixed-symmetry(MS) state. We have calculated the electric monopole strength ρ~2(E0,0_2~+→0_1~+), and our result agrees with the experimental one. The calculation indicates that shape coexistence and MS states are simultaneously well described using IBM-2.