[en] Eu²⁺ doped Sr_2-xBa_xSi₅N₈ phosphors were synthesized at 1610 ℃ for 4 h via the solid-state reaction method. The XRD results confirm that the complete solid solutions are formed. With the increase of x, the emission spectra show an obvious blue-shift from 610 nm to 585 nm under the excitation of 460 nm. The color tone can be tuned from yellow to red. The corresponding mechanism for the blue-shift of peak-wavelength is studied in detail. The results of decomposed Gaussian spectra and fluorescence lifetime show that the local coordination structure surrounding activator ions changes with increasing x value. It is found that the probability of Eu occupying Sr1 and Sr2 site is dependent on Ba/Sr ratio. The variation of thermal quenching properties and the corresponding mechanism is discussed in detail. The results indicate that Eu²⁺ doped Sr_2-xBa_xSi₅N₈ is a promising orange red-emitting phosphor for near UV or blue light-pumped white light-emitting-diodes (wLEDs). - Graphical abstract: Eu²⁺ doped Sr_2-xBa_xSi₅N₈ solid solutions were prepared by the solid-state reaction method. The structure, luminescence and thermal quenching properties with varying Ba/Sr ratio were investigated in detail. - Highlights: • The stucture and luminescence properties of Eu doped Sr_2-xBa_xSi₅N₈ phosphors were investigated. • The samples with the intermediate compositions(x=1.0,1.5) show better stability than the end members of both Sr₂Si₅N₈:Eu²⁺ and Ba₂Si₅N₈:Eu²⁺. • The possible mechanism for the improvement of thermal quenching properties was proposed.

[en] One of the proton halo candidates ²³Al and its isotopes are systematically investigated in the nonlinear Relativistic Mean-Field and Skyrme Hartree-Fock approaches. It is shown that there exists the energy inversion of (((5)/(2)))⁺(202) and (((1)/(2)))⁺(211) orbitals in ²³Al nucleus and which may produce the large enhancement of reaction cross section comparing with its neighboring nuclei. Meanwhile, it is obvious to see that the isospin effect of the pairing correlation plays a great role to the separation energy when the Al isotopes approach to the proton drip line. In addition, the ground state and excited state of ⁹B, ¹³N are also investigated in the RMF model. There may exist the halo structure in ¹³N when the last proton of ¹³N occupies in the first excited state

[en] Zinc oxide epilayer films were grown on vicinal cut sapphire substrates by pulsed laser deposition with in situ annealing oxygen pressures varied from 0 to 10 x 10³ Pa. The best crystalline quality was obtained for ZnO layer with annealing oxygen pressure of 6 x 10³ Pa. Laser induced thermoelectric voltage (LITV) were observed along the tilting angle orientation of the substrate when the pulsed KrF excimer laser of 248 nm were irradiated on the films. The largest LITV signal was measured for the film grown at 6 x 10³ Pa annealing oxygen pressure. According to the measured LITV signals, Seebeck anisotropy was evaluated and was found to range from 3 to 12 μV/K for ZnO films annealed at different oxygen pressures from 2 to 10 x 10³ Pa. It is suggested that oxygen ambient plays an important role in the electronic properties of the ZnO films.

[en] σ_R, σ_-n and σ_-2n have been calculated via the BUU model with soft EOS and 0.8 times of σ_Cug. The density distribution without any adjustable parameters which comes from the RMF model has been introduced into the BUU calculation to replace the normally used one-parameter square-type distribution. The calculated results can reproduce the experimental data well for both halo- and stable-nuclei-induced reactions. Here σ_-n or σ_-2n is calculated as the difference between σ_R of halo nucleus and core nucleus, by assuming σ_corr≅0. It indicates that this assumption works very well at high energy in the BUU calculation. More experimental measurements are necessary to test the validity of this assumption at intermediate energy. (orig.)

[en] The properties of three pairs of mirror nuclei ¹³N-¹³C, ¹⁵N-¹⁵O and ²¹Na-²¹Ne (these mirror nuclei are all made of a good inert core plus an unpaired valence nucleon) are investigated by using the nonlinear relativistic mean-field (RMF) theory. It is found that the calculated binding energies with two different parameter sets are very close to the experimental ones for both the ground states and the excited states except for the large deformed nuclei. The calculations show that the 2s_1/2 excited states of ¹⁵N and of ²¹Na are both weakly bound with a proton halo and a proton skin (or a pigmy proton skin), respectively. In addition, the 1d_5/2 excited state of ¹³C and the 2s_1/2 excited state of ¹⁵O are also weakly bound with a neutron skin, respectively. The ratio of the valence nucleon radius to matter radius is deduced and it can be regarded as an additional criterion for the existence of exotic structure. The unbound 2s_1/2 and 1d_5/2 excited states of ¹³N are also discussed. (orig.)

[en] The absolute inclusive branching fraction of D_s⁺→φX⁺ has been measured from data collected by the BES detector at a center-of-mass energy of 4.03 GeV, corresponding to an integrated luminosity of 22.3 pb^-1. At this energy, direct pair production e⁺e^-→D_s⁺D_s^- has been observed. We have selected D_s candidate events by reconstructing five hadronic decay modes D_s⁺→φπ⁺, bar K^0*K⁺, bar K⁰K⁺, f₀π⁺ and K⁰K^-π⁺π⁺ and have searched for inclusive φ close-quote s in the recoiling D_s^-. We observed three recoiling φ close-quote s in the 166.4 ± 31.8 D_s candidate events, which leads to the absolute branching fraction B(D_s⁺→φX⁺)=(17.8_-7.2^+15.1_-6.3^+0.6) % and B(D_s⁺→φπ⁺)=(3.6_-1.6^+3.1_-1.3^+0.4) %. copyright 1997 The American Physical Society

[en] The mass of the τ lepton has been measured at the Beijing Electron-Positron Collider using the Beijing Spectrometer. A search near threshold for e⁺e-→τ⁺τ^- was performed. Candidate events were identified by requiring that one τ decay via τ→eν bar ν, and the other via τ→μν bar ν. The mass value, obtained from a fit to the energy dependence of the τ⁺τ^- cross section, is m_τ=1776.9_-0.5^+0.4±0.2 MeV