The Association Geranio phaei-Urticetum dioicae in Southwest Poland

<p>Based on 39 phytosociological relevés Geranio phaei-Urticetum dioicae, a poorly known association of nitrophilous saum-communities occurring in the mountains of Central Europe was characterized. Its ecological requirements as well as distribution in Poland and Central Europe were presented and discussed. Five new subassociations of the Geranio phaei-Urticetum dioicae (G.-U. arrhenatheretosum elatioris, G.-U. typicum, G.-U. festucetosum giganteae, G.-U. senecionetosum fuchsii and G.-U. rumicetosum alpestris), have been distinguished on the basis of different species composition.</p

Interactions of transition metal atoms with He

The adiabatic interaction potentials were obtained for the paradigm transition metal-rare gas interactions: Sc(2D)–He and Ti(3F)–He and their di-cations. The ab initio approach included the coupled cluster and multireference configuration interaction methods. He atoms form very weak van der Waals complexes with Sc and Ti with well-depths of ca. 4–5 cm-1. The interactions are characterized by the nearly-degenerate manifolds of adiabatic states with splittings of the order of 0.1 cm-1 or less. The anisotropy of the Ti–He interaction is smaller than that for the Sc–He interaction. The origin of the weak anisotropy of these interactions was analyzed. The exchange repulsion was found to be nearly the same in the ${\rm \Sigma}$, ${\rm \Pi}$ and ${\rm \Delta}$ states due to the valence d-electrons being submerged under the doubly filled 4s electron sub-shell. The anisotropy of the total potential is controlled by the weakly-anisotropic dispersion interaction

On the Nature of Luminescence Thermochromism of Multinuclear Copper(I) Benzoate Complexes in the Crystalline State

A model luminescent [(PhCO2)4Cu4] (Cu4) complex in the crystalline state was investigated via combined crystallographic and spectroscopic techniques contributed substantially by theoretical modelling. The complex appeared to exhibit luminescence thermochromism, i.e., red phosphorescence at room temperature which changes to green when lowering the temperature to 90 K. The low-energy emissive state was assigned as a cluster-centred triplet, 3CC. The emission from this state predicted in TDDFT (~635 nm) matches the experimental red band observed at 660&ndash;715 nm. In contrast, the nature of the high-energy &ldquo;green&rdquo; band was less straightforward. The next reached cluster-centred triplet excited state occurred to be energetically close to the experimental value of ~545 nm. The two excited states also exhibit significant metal-to-ligand and ligand-to-metal charge transfer characteristics, especially for solid-state distorted geometries. In both cases the cluster core was expected to become notably contracted when compared to the ground state. Time-resolved photocrystallographic results supported the computationally predicted core contraction upon excitation. Additionally, the differences between the spectroscopic behaviour of the related tetra- and hexanuclear copper(I) complexes, Cu4 and Cu6 (i.e., [(PhCO2)6Cu6]) in the crystalline state were discussed and examined. It appeared that crystal packing may constitute an important factor as far as the lack of luminescence thermochromism in the latter case is concerned. Synopsis: Structure&ndash;property relationships characterising a model luminescent [(PhCO2)4Cu4] (Cu4) complex in the crystalline state were investigated via combined crystallographic and spectroscopic techniques contributed by theoretical modelling, and compared with the properties of the related [(PhCO2)6Cu6] (Cu6) complex

Coincidence resolution time of two small scintillators coupled to high quantum-efficiency photomultipliers in a PET-like system

The lower limit of the time resolution for a positron emission tomography (PET) system has been measured for two scintillator types, LYSO:Ce and LuAG:Pr. Small dimension crystals and ultra bi-alkali phototubes have been used in order to increase the detected scintillation photons. Good timing resolutions of 118 ps and 223 ps FWHM have been obtained for two LYSO and two LuAG, respectively, exposed to a 22Na source