Kari O. Eskola

The Bologna Stone: history's first persistent luminescent material

In 1603, the Italian shoemaker Vincenzo Cascariolo found that a stone (baryte) from the outskirts of Bologna emitted light in the dark without any external excitation source. However, the calcination of the baryte was needed prior to this observation. The stone later named as the Bologna Stone was among the first luminescent materials and the first documented material to show persistent luminescence. The mechanism behind the persistent emission in this material has remained a mystery ever since. In this work, the Bologna Stone (BaS) was prepared from the natural baryte (Bologna, Italy) used by Cascariolo. Its properties, e. g. impurities (dopants) and their valences, luminescence, persistent luminescence and trap structure, were compared to those of the pure BaS materials doped with different (transition) metals (Cu, Ag, Pb) known to yield strong luminescence. The work was carried out by using different methods (XANES, TL, VUV-UV-vis luminescence, TGA-DTA, XPD). A plausible mechanism for the persistent luminescence from the Bologna Stone with Cu+ as the emitting species was constructed based on the results obtained. The puzzle of the Bologna Stone can thus be considered as resolved after some 400 years of studies. (Less)

Predictions for 5.023 TeV Pb + Pb collisions at the CERN Large Hadron Collider

H. Niemi, K. J. Eskola, R. Paatelainen, K. Tuominen Institut für Theoretische Physik, Johann Wolfgang Goethe-Universität, Max-von-Laue-Str. 1, D-60438 Frankfurt am Main, Germany University of Jyvaskyla, Department of Physics, P.O. Box 35, FI-40014 University of Jyvaskyla, Finland Helsinki Institute of Physics, P.O.Box 64, FI-00014 University of Helsinki, Finland Departamento de Fisica de Particulas, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela, Galicia, Spain and Deparment of Physics, University of Helsinki, P.O. Box 64, FI-00014 University of Helsinki, Finland

Luminescence properties of Eu3+ and TiIV/ZrIV doped yttrium oxysulfides (Y2O2S:Eu3+,TiIV/ZrIV)

The red emitting Y2O2S:Eu3+,TiIV (or ZrIV, xEu: 0.01, xTi/Zr: 0.003/0.015/0.03) materials were prepared with a flux method. According to X-ray powder diffraction, the materials have the hexagonal crystal structure. The UV excited (λexc: 250 nm) emission maximum was observed at 628 nm due to the 5D0→7F2 transition of Eu3+. The excitation spectra (λem: 628 nm) consist of broad bands centered at 240 and 320 nm due to the charge transfer transitions O2−→Eu3+ and S2−→Eu3+, respectively. Red persistent luminescence was observed with a maximum at 628 nm, as well. Persistent luminescence was the strongest with the TiIV co-doping though the intensity of persistent luminescence decreased with the increasing amount of both the TiIV and ZrIV co-dopants. The thermoluminescence (TL) glow curves of the Y2O2S:Eu3+,TiIV materials consist of bands at ca. 110 and 200 °C. In Y2O2S:Eu3+,ZrIV, similar bands are observed at lower temperatures viz. at ca. 100 and 180 °C. TL weakens when the amount of co-dopants is increased. The TiIV co-doped materials have stronger TL than the ZrIV co-doped materials. The deconvolution of TL glow curves revealed three distinct traps with depths ranging from 0.6 to 1.0 eV.

Predictions for multiplicities and flow harmonics in 5.44 TeV Xe+Xe collisions at the CERN Large Hadron Collider

We present the next-to-leading-order event-by-event EKRT model predictions for the centrality dependence of the charged hadron multiplicity in the pseudorapidity interval

First direct age determination for the Baltic Ice Lake/Yoldia Sea transition in Finland

|\eta|\le 0.5

Aerial LiDAR analysis in geomorphological mapping and geochronological determination of surficial deposits in the Sodankylä region, northern Finland

, and for the centrality dependence of the charged hadron flow harmonics

Luminescence dating of a coastal Stone Age dwelling place in Northern Finland

v_n\{2\}

Far Beta-Unstable Alpha-Particle Emitting Nuclei

obtained from 2-particle cumulants, in

Middle Weichselian glacial event in the central part of the Scandinavian Ice Sheet recorded in the Hitura pit, Ostrobothnia, Finland

\sqrt{s_{NN}}=5.44

Event-by-event fluctuations in a perturbative QCD + saturation + hydrodynamics model: Determining QCD matter shear viscosity in ultrarelativistic heavy-ion collisions

TeV Xe+Xe collisions at the CERN Large Hadron Collider. Our prediction for the 0-5 \% central charged multiplicity is