White light emission from Tm/Dy co-doped oxyfluoride germanate glasses under UV light excitation

In this paper, we report on the absorption and photoluminescence properties of Tm³⁺/Dy³⁺ ions co-doped oxyfluoride germanate glasses for white light emission. The X-ray diffraction (XRD) and differential thermal analysis (DTA) profiles of the host glass have been carried out to confirm its structure and thermal stability. From the measured absorption spectra, Judd-Ofelt (J-O) intensity parameters (Ω₂, Ω₄ and Ω₆) have been evaluated for Tm³⁺ and Dy³⁺ ions. A combination of blue, yellow and red emissions has emerged in these glasses, which allows the observation of bright white light when the glasses are excited by the ultraviolet light. The white light luminescence colour could be changed by varying the excitation wavelength. Also, various colours of luminescence, including white light, can be easily tuned by adjusting the concentrations of Tm³⁺ or Dy³⁺ ions in the co-doped glasses. Concentration quenching effect was also investigated and possible energy transfer mechanism from Dy³⁺→Tm³⁺ ions was explained which is also confirmed by the decay lifetime measurements.     

Addendum and Corrigendum： ＂Heavy Quarkonium Spectra in a Quark Potential Model＂

In a paper published years ago by me and my collaborators, the properties of heavy quarkonium systems were studied based on the Dick potential, which explicitly included the color factor in the potential and the non-relativistic SchrSedinger equation was numerically solved. However, another paper by Barakat and Chaba appeared online a few months earlier, which dealt with a similar problem, but used the shifted-expansion technique （SLET） to solve the semi-relativistic wave equation for the Dick potential up to a QCD color factor. Since both the papers solved the same Dick potential model, similar energy spectra due to the small relativistic effect were obtained for this heavy quark system. I and my collaborators did not point out this similarity in Ref. This should be added to give credit to Ref.     

Upconversion Luminescence of Er3+ Ions in Transparent Germanate Glass Ceramics Containing CaF2 Nanocrystals

The visible upconversion and near-infrared luminescence of Er3＋ ions in germanate glass ceramics containing GaF2 nanocrystals are investigated. The nanocrystals are characterized by x-ray diffraction （XRD） and transmission electron microscopy, showing their mean sizes less than 20hm. High transmittance of the glass ceramics is displayed by absorption spectra. The upconversion luminescence intensity in the glass ceramics increases significantly with increasing temperature. Both the shifts of the XRD peaks and the Stark-split shown in the luminescence spectra indicate the entrance of the Er3＋ ions into the CaF2 nanocrystals, which is confirmed by a Judd-Ofelt analysis. Possible mechanisms of the upconversion luminescence are analyzed.     

Effects of non-stoichiometry on crystallinity, photoluminescence and afterglow properties of Sr2MgSi2O7:Eu, Dy phosphors

Eu²⁺, Dy³⁺ co-doped Sr₂MgSi₂O₇ phosphors with deficient, stoichiometric or excess amounts of silicon are prepared by solid-state reaction. XRD and SEM results indicate that all the samples studied are found to be free from impurities and samples with SiO₂ excess possess better crystallinity and larger grain size. Photoluminescence reveals that the position of Eu²⁺ emission is not changed with various compositions. However, both photoluminescence intensity and afterglow properties are increased by an incorporation of excess SiO₂ and are decreased by SiO₂ deficiency. The thermoluminescence results show that the corresponding increase or decrease in afterglow is associated with trap density, but no change in trap depth. The underlying reason of photoluminescence and afterglow enhancement is discussed.     

Energy transfer and frequency upconversion in Yb3+–Er3+-doped PbO-GeO2 glass containing silver nanoparticles

We report the infrared-to-visible frequency upconversion in Er³⁺–Yb³⁺-codoped PbO-GeO₂ glass containing silver nanoparticles (NPs). The optical excitation is made with a laser at 980 nm in resonance with the ²F_5/2→²F_7/2 transition of Yb³⁺ ions. Intense emission bands centered at 525, 550, and 662 nm were observed corresponding to Er³⁺ transitions. The simultaneous influence of the Yb³⁺→Er³⁺ energy transfer and the contribution of the intensified local field effect due to the silver NPs give origin to the enhancement of the whole frequency upconversion spectra.     

Ordered macroporous gold thin film with encaptured polymer spheres

A two-dimensional colloidal crystal fabricated from core-shell polystyrene spheres was employed as a template for the electrochemical deposition of gold. By partially embedding the colloidal spheres into the gold film and selectively removing the shells of the colloidal spheres, highly ordered macroporous gold thin films with captured polystyrene spheres were obtained.     

The effect of oxalic and sulfuric ions on the photoluminescence of anodic aluminum oxide formed in a mixture of sulfuric and oxalic acid

Anodic aluminum oxide (AAO) films with highly ordered pore arrays were prepared in sulfuric, oxalic acids and their mixture solutions, respectively. The photoluminescence (PL) measurements show that AAO films formed in the mixture electrolytes have PL bands in the wavelength range of 300–450 nm, which mainly arise from the oxalic impurities incorporated into AAO films. However, the sulfuric ions have a strong effect on the PL bands. With the increase of the concentration of sulfuric ions in the mixture electrolyte, the blueshift of the PL bands occurs from 410 to 345 nm. The reasons of the results are being discussed.     

Study of jet fragmentation in p+p collisions at 200 GeV in the STAR experiment

The measurement of jet fragmentation functions in p+p collisions at 200 GeV is of great interest because it provides a baseline to study jet quenching in heavy-ion collisions. It is expected that jet quenching in nuclear matter modifies the jet energy and multiplicity distributions, as well as the jet hadrochemical composition. Therefore, a systematic study of the fragmentation functions for charged hadrons and identified particles is a goal both in p+p and Au+Au collisions at RHIC. Studying fragmentation functions for identified particles is interesting in p+p by itself because it provides a test of NLO calculations at RHIC energies. We present a systematic comparison of jet energy spectra and fragment distributions using different jet-finding algorithms in p+p collisions in STAR. Fragmentation functions of charged and neutral strange particles are also reported for different jet energies.     

Energy and system dependence of high-<Emphasis Type="Italic">p</Emphasis><Subscript><Emphasis Type="Italic">T</Emphasis></Subscript> triggered two-particle near-side correlations

Previous studies have indicated that the near-side peak of high-p _T triggered correlations can be decomposed into two parts, the Jet and the Ridge. We present data on the yield per trigger of the Jet and the Ridge from d+Au, Cu+Cu and Au+Au collisions at GeV and 200 GeV and compare data on the Jet to PYTHIA 8.1 simulations for p+p. PYTHIA describes the Jet component up to a scaling factor, meaning that PYTHIA can provide a better understanding of the Ridge by giving insight into the effects of the kinematic cuts. We present collision energy and system dependence of the Ridge yield, which should help distinguish models for the production mechanism of the Ridge.     

Recent charm measurements through hadronic decay channels with STAR at RHIC in 200 GeV Cu+Cu collisions

We report on the measurements of D ⁰ and D _s meson production in 200 GeV Cu+Cu collisions at the STAR at RHIC experiment. Results are discussed with reference to pQCD predictions of the open charm cross-section as well as the statistical hadronization model.