A MICROSCOPIC STUDY OF THE LOW-LYING LEVELS OF 18O AND 18F WITH THE SKYRME INTERACTION

The low-lying levels of ¹⁸O and ¹⁸F have been calculated using several Skyrme interactions and the many-body folded diagram theory of Kuo, Lee and Ratcliff. Our results obtained with the Skyrme interactions determined by Vautherin and Brink and by Krewald are not in satisfactory agreement with the experimental spectra.     

PION-18O INELASTIC SCATTERING

In the framework of the eikonal form of DWIA and using the transition densitymethod, the differential cross sections for ¹³O (π,π') .¹⁸O^* (2⁺, 1.98 MeV) inelasticscattering at T_π=230 MeV are calculated. The ratios of the integrated cross sectionsfor π^- vs. π⁺ bombardments, are analyzed and the effects of changing the neutron radiusto the differential cross sections are studied as well. Our results fit the data quite well.     

Angular Distribution of Elastic Scattering of 17F and 18Ne on Proton

Under reverse kinematics, elastic scattering of ¹⁷F and ¹⁸Ne on proton is studied. The experimental differential cross sections were measured. A kind of global optical potential with the CH89 parameters is used to describe the radioactive nucleus as an initial optical potential parameters. The experimental differential cross section data are analyzed by using the theoretical calculation code DWUCK4 with the distorted wave Born approximation and parameter search subroutine ABOD which automatically searches the suitable parameters. Then the optical potential parameters of scattering ¹⁷F and ¹⁸Ne on proton are obtained. From the analyses of the optimized parameters, the real central potential mean square radii of ¹⁷F and ¹⁸Ne, 3.239fm and 3.317fm are deduced, respectively.     

BOUND STATES OF ETA-24Mg AND ETA-32S

The Eta-²⁴Mg mesic mucleus and the Eta-³²S mesic nucleus are considered as the ¹²C-Eta-¹²C and ¹⁶O-Eta-¹⁶O three body systems respectively.With the separable potentials which include only S-wave Eta-¹²C and Eta-¹³O interadtions as the effective interactions,the Schrodinger equa tions of the systems are solved in the Born-Oppenheimer approximation.The two-center problems are solved exactly first,and then the binding-energies of Eta-²⁴Mg and Eta-³²S are calculated.The calculated results are satisfactory.     

Further Studies on Halo Nuclei 11Li,14Be and 17B

Based on the three-body model with Yukawa interactions,the halo nuclei ¹¹Li,¹⁴Be and ¹⁷B are further studied by the variation calculation.An analytical expression for the density distribution of the halo neutron is given.The theoretical resultsagree with the recent experimental data.     

A Three-Body Model of 11Li,14Be and 17B

The nuclei ¹¹Li,¹⁴Be and ¹⁷B are considered as three-body systems composed of the N=2Z core and two outside neutrons.The core-neutron and neutronneutron interactions are assumed to be the attractive exponential potentials.It has been shown that the three-body system can have a bound state although any two constituents of the system cannot have a bound state. The experimental data of the binding energy and extraordinarily large matter root-mean-square radius can be explained in the frame of the three-body model.     

Neutron Yields and Neutron Emission Rate in the ForwardDirection for 50 MeV/u 18O-ion on Thick Be,Cu,Au Targets

The neutron yields and the neutron emission rates in the forward direction for 50MeV/u ¹⁸O-ion induced reactions on thick Be, Cu, Au targets have been measured using the threshold detector activation method. The measured results indicate that the neutron yield and the neutron emission rate depend on the atomic number of target nuclei; neutron yield for the lighter target is greater than that for the heavier one. The neutron yield for 50MeV/u ¹⁸O-ion on Cu is about four times as large as that for 50MeV/u ¹²C-ion on Cu when incident energies per nucleon are identical.     

Cross Section Measurements of Neutron-Rich Hg Isotopes in Reaction of 28MeV/u 18O with Thick Natural Lead Target

By using 28MeV/u ¹⁸O beam,an on-line melting lead target equipment and 4π-ΔEβ-γcoincident technique,the relative cross section ratios and absolute cross sections of neutron-rich nuclides ^205—208Hg have been measured. The production cross section of ²⁰⁹Hg is extrapolated.The cross section of ²⁰⁷Hg produced by-2p +1n from target decreases suddenly,which may be explained by change of reaction Q value.     

Variable Phase Method Used to Calculate Ultracold Scattering Properties of 7Li33Cs

Elastic scattering properties of singlet and triplet states of ^7 Li^133 Cs at ultralow temperatures are calculated using the constructed potential curves gleaned from high-precision spectroscopy measurement. We show how to reach the scattering length and the number of bound states via the vaxiable phase method. The scattering lengths of the singlet and triplet states of^7 Li^133 Cs are 50.5 a.u. and -135.7 a.u., respectively. We derive two corrections, arising from long range interactions, accurately to at least first order, which provide upper and lower computed bounds to the scattering length. Our results are consistent with the recent experimental data and the theoretical calculation.     

Neutron Halo Structure of 11Li

The neutron rich nucleus ¹¹Li is considered as a three-body system composed of ⁹Li core and two outside neutrons.The coreneutron and neutron-neutron interactions are chosen to be of the attractive exponential potentials.The Shrdinger equation is solved by diagonalizing the Hamiltonian with the aid of the harmonic oscillator formalism. The structure of this system and the interparticle correlation are investigated by inspecting the shape-density and the neutron halo structure is obtained.     

Study of Quasiparticles Bands in Odd-Odd 188Au

High-spin level structure of ¹⁸⁸Au has been studied via the ¹⁷³Yb(¹⁹F, 4nγ) reaction using techniques of in-beam γ-ray spectroscopy. Based on the experimental results, the level scheme of ¹⁸⁸Au has been revised significantly. The previously reported positive parity levels have been modified and a new 20⁺ level was proposed to feed the 18⁺ states via two low-energy transitions. The existence of the 20⁺ and the level structures above it are similar to those in the neighboring odd-odd ^190,192Au,therefore, the π h_{11/2}^{-1}\otimes \upnu i_{13/2}^{-2} h_{9/2}^{-1} configuration was assigned to the 20⁺ state.     

Vacuum Ultraviolet Excited Photoluminescence Properties of Novel Na3Y9O3（BO3）8：Tb^3＋ Phosphor

The novel vacuum ultraviolet （VUV） excited Na3 Y9O3 （BO3）8：Tb^3＋ （NYOB：Tb^3＋） green phosphor is prepared. Strong VUV photoluminescence and high quenching concentration of Tb^3＋ （20 wt%） are observed in NYOB： Tb^3＋ and the strong emission are correlated with the unique layer-type structure of NYOB. All the characteristic 4 f - 5d transitions of Tb^3＋ and the host absorption band in VUV region are identified in the excitation spectrum. Based on the results, the energy levels scheme of Tb^3＋ in NYOB：Tb^3＋ is first established. This newly developed NYOB：Tb^3＋ phosphor shows excellent optical properties when compared with the commercial Zn2SiO4：Mn^2＋ and would be a potential VUV-excited green phosphor.     

Optical Potential Parameters for Halo Nucleus System ^6He＋^12C from Transfer Reaction ^11B（^7Li, ^6He）^12C

The optical potential parameters for the halo nucleus system ^6He＋^12C are extracted from fits to the measured angular distributions of ^11B（^7Li, ^6He）12C reaction at energies of 18.3 and 28.3MeV with distorted-wave Born approximation analysis. The characters of the obtained optical potentiM parameters are basically consistent with the results extracted from the fits to the elastic-scattering angular distributions in the literature.     

Theoretical Study of Interesting Fine-Structure Splittings for 23P0, 1, 2 States along Helium Isoelectronic Sequence

Using the multi-configuration Dirac Fock method including the Breit interactions and QED corrections, we calculate the fine-structure energy levels of the 2^3 Po, 1,2 states along the helium isoelectronic sequence with atomic number up to Z = 36, where LS-coupling is appropriate. Our calculation results agree with the experimental results within about 1%. We elucidate the mechanism of the interesting fine-structure splittings for the 2^3Po,1,2 states along the helium isoelectronic sequence, i.e. the competitions between the spin-orbit interactions and the Breit interactions which represent the relativistic retardation effect of electromagnetic interactions.     

Correction of 24Mg Collective States With Three-Body Non-diagonal Boson Interaction

Although it has been verified that the interacting boson model (IBM) can be applied to light nuclei in sd shell successfully, the deficiency shll exists. The level of experimental spectrum of ²⁴Mg is much higher than 3. The similar result can not be obtained by using of conventional IBM, in which only one-body and two-body interactions are concerned. Three-body interactions have been discussed by some authors, but the authers mainly considered the diagonal interactions. Moreover,the defect mentioned above can not be solved with these interactions. Introducing three-body non-diagonal interaction, the energy levels of ²⁴Mg are calculated, the difficulty of low 0 theoretical level is overcome and the coincidence betWeen theory and experiment is improved. This work illustrates that in some cases the three-body non-diagonal boson interaction is important.     

High-Spin States and Negative Parity Levels in Neutron-Rich 116,118,120Cd Nuclei

High spin states in neutron-rich ^116,118,120Cd nuclei have been investigated by observing high-fold prompt γ-ray coincidence events from the spontaneous fission of ²⁵²Cf with the Gammasphere detector array. The yrast bands have been extended with spin up to 18h in¹¹⁸Cd and 16h in ^116,120Cd respectively. The band structures are calculated using the cranked shell model and possible origination for the backbends in the yrast bands is discussed. Proposed 5^－ and 7^－ levels are observed in each of these cadmium isotopes, and possible explanation for the negative states is discussed based on systematic comparison. A quasi-rotational band based on 7^－ level in ¹¹⁸Cd has been established.     

Quantum cutting downconversion by cooperative energy transfer from Bi3+ to Yb3+ in Y2O3 phosphor

Bi~(3+) and Yb~(3+) codoped cubic Y2O3 phosphors are prepared by pechini sol-gel method.Strong near-infrared (NIR) emission around 980 nm from Yb~(3+)(2F5/2 → 2F7/2) is observed under ultraviolet light excitation.A broad excitation band ranging from 320 to 360 nm,owing to the 6s 2 →6s6p transition of Bi~(3+) ions,is recorded when the Yb~(3+) emission is monitored,which suggests a very efficient energy transfer from Bi~(3+) ions to Yb~(3+) ions.The Yb~(3+) concentration dependences of both the Bi~(3+) and the Yb~(3+) emissions are investigated.The decay curve of Bi ~(3+) emission under the excitation of 355 nm pulse laser is used to explore the Bi~(3+) →Yb~(3+) energy transfer process.Cooperative energy transfer (CET) is discussed as a possible mechanism for the near-infrared emission.     

Preparation and Luminescence Characteristics of Ca3Y2（BO3）4：Eu^3＋ Phosphor

Ca3Y2 （BO3）4：Eu^3＋ phosphor is synthesized by high temperature solid-state reaction method, and the Iuminescence characteristics are investigated. The emission spectrum exhibits two strong red emissions at 613 and 621 nm corresponding to the electric dipole ^5 Do- ^7F2 transition of Eu^3＋ under 365 nm excitation, the reason is that Eu^3＋ substituting for Y^3＋ occupies the non-centrosymmetric position in the crystal structure of Ca3 Y2 （BO3）4. The excitation spectrum for 613 nm indicates that the phosphor can be effectively excited by ultraviolet （UV） （254 nm, 365nm and 400nm） and blue （470nm） light. The effect of Eu^3＋ concentration on the emission intensity of Ca3 Y2 （BO3）4 ：Eu^3＋ phosphor is measured, the result shows that the emission intensities increase with increasing Eu^3＋ concentration, then decrease. The CIE colour coordinates of Ca3Y2 （BO3）4：Eu^3＋ phosphor is （0.639, 0.357） at 15mol% Eu^3＋.     

Identification of New Isotope 238Th

Unreported heavy neutron-rich nuclide ²³⁸Th has been produced via a multinucleon transfer reaction by 60MeVIu ¹⁸0 ions bombardment of natural uranium.Thorium was radiochemically separated from the mixture of uranium and reaction products. ²³⁸Pa as a daughter nucleus of ²³⁸Th has been identified according to the growth and decay of ²³⁸Pa γ rays which has been observed. The half-life of ²³⁸Th was determined to be (9.4 + 2.0) min. At the same time, a new γ ray of (89.0 + 0.3) keV with T_1/2= (8.9 + 1.5)min was found in the γ spectrum gated with the K_α1, X ray of Pa and assigned to ²³⁸Th decay based on the measurements of its transition energy and the half-life.

     

Mixing between the 23S1 and 13D1 Ds

Mixing between the 2³S₁ and 1³D₁ D_s is studied within the ³P₀ model. If mixing between these two 1^- states exists, D_s1^*(2700)^± and D_sJ^*(2860)^± could be interpreted as the two orthogonal mixed states with mixing angle θ≈ -80° in the case of a special β for each meson. However, in the case of a universal β for all mesons, D_s1^*(2700)^± could be interpreted as the mixed state of 2³S₁ and 1³D₁ with mixing angle 12° < θ < 21° but D_sJ^*(2860)^± seems difficult to interpret as the orthogonal partner of D_s1^*(2700)^±.