Investigation of indirect excitons in bulk 2H-MoS using transmission electron energy-loss spectroscopy.

We have investigated indirect excitons in bulk 2H-MoS using transmission electron energy-loss spectroscopy. The electron energy-loss spectra were measured for various momentum transfer values parallel to the [Formula: see text] and [Formula: see text] directions of the Brillouin zone. The results allowed the identification of the indirect excitons between the valence band K and conduction band Λ points, the Γ and K points as well as adjacent K and [Formula: see text] points.

Semiconductor-to-metal transition in the bulk of WSe upon potassium intercalation.

We present electron energy-loss spectroscopic measurements of potassium (K) intercalated tungsten diselenide (WSe). After exposure of pristine WSe films to potassium, we observe a charge carrier plasmon excitation at about 0.97 eV, which indicates a semiconductor-to-metal transition.

Environmental effects on stem water deficit in co-occurring conifers exposed to soil dryness.

We monitored dynamics of stem water deficit (ΔW) and needle water potential (Ψ) during two consecutive growing seasons (2011 and 2012) in a dry inner Alpine environment (750 m above sea level, Tyrol, Austria), where Pinus sylvestris, Picea abies and Larix decidua form mixed stands. ΔW was extracted from stem circumference variations, which were continuously recorded by electronic band dendrometers (six trees per species) and correlations with environmental variables were performed. Results revealed that (i) ΔW reached highest and lowest values in P.

Comparing growth phenology of co-occurring deciduous and evergreen conifers exposed to drought.

Plant phenological events are influenced by climate factors such as temperature and rainfall. To evaluate phenological responses to water availability in a Spring Heath-Pine wood (Erico-Pinetum typicum), the focus of this study was to determine intra-annual dynamics of apical and lateral growth of co-occurring early successional and and late successional exposed to drought. The effect of reduced plant water availability on growth phenology was investigated by conducting a rainfall exclusion experiment.

Age-dependent climate-growth relationships and regeneration of in a drought-prone mixed coniferous forest in the Alps.

Within dry inner Alpine environments climate warming is expected to affect the development of forest ecosystems by changing species composition and inducing shifts in forest distribution. By applying dendroecological techniques we evaluated climate sensitivity of radial growth and establishment of in a drought-prone mixed-coniferous forest in the Austrian Alps. Time series of annual increments were developed from > 220 trees and assigned to four age classes.

Drought sensitivity of three co-occurring conifers within a dry inner Alpine environment.

We applied dendroclimatological techniques to determine long-term stationarity of climate-growth relationships and recent growth trends of three widespread coniferous tree species of the central Austrian Alps, which grow intermixed at dry-mesic sites within a dry inner Alpine environment (750 m asl). Time series of annual increments were developed from > 120 mature trees of and . Calculation of response functions for the period 1911 - 2009 revealed significant differences among species in response to climate variables.

Momentum dependence of the excitons in pentacene.

We have carried out electron energy-loss investigations of the lowest singlet excitons in pentacene at 20 K. Our studies allow to determine the full exciton band structure in the a∗, b∗ reciprocal lattice plane. The lowest singlet exciton can move coherently within this plane, and the resulting exciton dispersion is highly anisotropic.

Effect of charge order on the plasmon dispersion in transition-metal dichalcogenides.

We investigate the dispersion of the charge carrier plasmon in the three prototypical charge-density wave bearing transition-metal dichalcogenides 2H-TaSe(2), 2H-TaS(2), and 2H-NbSe(2) employing electron energy-loss spectroscopy. For all three compounds the plasmon dispersion is found to be negative for small momentum transfers. This is in contrast with the generic behavior observed in simple metals as well as the related system 2H-NbS(2), which does not exhibit charge order.

Imaging single quantum dots in three-dimensional photonic crystals.

Performing fluorescence wide-field microscopy we have imaged single semiconductor quantum dots deep inside a 3-dimensional photonic crystal prepared from colloidal polymer beads. Exploring the emission diffraction patterns in defocused images of quantum dots we demonstrate that the direction-dependent photonic stop band imprints an anisotropy to the angular emission of a single quantum dot. Hence a single, quasi-point-like emitter is manipulated to radiate its photons only to certain well-defined directions by means of the anisotropic light propagation in photonic crystals.