High-energy Spectral Region Research Articles

Global rainstorm multi-attribute variation and its multiscale correlation with ENSO

This research uses a variety of statistical methods to diagnose the multi-attribute time series characteristics of global rainstorms and its response to ENSO from the perspective of land-ocean differentiation. The results showed that: (1) The global, global land and global ocean rainstorm and their contribution rates showed an increasing trend from 1979 to 2016. While, the global, global land and global ocean total rainfall showed an decreasing trend. The global land total rainfall showed a distinct sectional change pattern, which first increased from 1979 to 2006 and then decreased from 2007 to 2016. The comparison between the rainstorm and the total rainfall in global land and ocean showed that the rainstorm tended to increase in both ocean and land regions from 1979 to 2016, while the weak intensity rainfall tends to decrease in the globe. (2) The global land and ocean rainstorm and total rainfall did not change consistently on multiple time scales from 1979 to 2016, but showed inverse phase or forward and lag phase correlation. Fourthly, compared with ENSO, global land (ocean) rainstorm changed earlier (lag) in high energy spectral region. Compared with ENSO changes in low energy spectral region, global land rainstorm changes were consistent or ahead of time, while global ocean rainstorm changes were mainly ahead of time compared with ENSO changes.

Global Rainstorm Temporal Variation from 1979 to 2016 Based on the Perspective of Land-Ocean Differentiation

Based on the ERA-Interim precipitation data from 1979 to 2016, this paper uses a variety of statistical methods to diagnose the multi-attribute time series characteristics of global rainstorms and its response to ENSO from the perspective of land-ocean differentiation. The results showed as follows. (1) The global, global land and global ocean rainstorm and their contribution rates showed an increasing trend from 1979 to 2016. The global, global land and global ocean total rainfall showed an decreasing trend. The global land total rainfall showed a distinct sectional change pattern, which first increased from 1979 to 2006 and then decreased from 2007 to 2016. The comparison between the rainstorm and the total rainfall in global land and ocean showed that the rainstorm tended to increase in both ocean and land regions from 1979 to 2016, while the weak intensity rainfall tends to decrease in the globe. (2) The results of MK mutation test showed that the global, global land and global ocean rainstorm changed abruptly in the year of 2006, 1999 and 2008, respectively, without passing the 0.05 significance level test. The global, global land and global ocean total rainfall changed abruptly in the year of 1998, 2014 and 1994, respectively, and passed the test of 0.05 significance level. The rainstorm contribution rates of global, global land and global ocean changed abruptly in the year of 2006, 2003 and 2007, respectively. Only global land rainstorm and global ocean rainstorm passed the 0.05 significance level test. The year of abruptly change of global rainstorm and total rainfall were consistent with the year of ENSO warm event or the year of transition from cold event to warm event. (3) The global land and ocean rainstorm and total rainfall did not change consistently on multiple time scales from 1979 to 2016, but showed inverse phase or forward and lag phase correlation. Fourthly, compared with ENSO, global land (ocean) rainstorm changed earlier (lag) in high energy spectral region. Compared with ENSO changes in low energy spectral region, global land rainstorm changes were consistent or ahead of time, while global ocean rainstorm changes were mainly ahead of time compared with ENSO changes.

Carrier concentration dependent photoluminescence properties of Si-doped InAs nanowires

We report the effects of intentional n-type doping on the photoluminescence (PL) properties of InAs nanowires (NWs). Employing silicon (Si) as a dopant in molecular beam epitaxy grown NWs, the n-type carrier concentration is tuned between 1 × 1017 cm−3 and 3 × 1018 cm−3 as evaluated from Fermi-tail fits of the high-energy spectral region. With the increasing carrier concentration, the PL spectra exhibit a distinct blueshift (up to ∼50 meV), ∼2–3-fold peak broadening, and a redshift of the low-energy tail, indicating both the Burstein-Moss shift and bandgap narrowing. The low-temperature bandgap energy (EG) decreases from ∼0.44 eV (n ∼ 1017 cm−3) to ∼0.41 eV (n ∼ 1018 cm−3), following a ΔEG ∼ n1/3 dependence. Simultaneously, the PL emission is quenched nearly 10-fold, while the pump-power dependent analysis of the integrated PL intensity evidences a typical 2/3-power-law scaling, indicative of non-radiative Auger recombination at high carrier concentrations. Carrier localization and activation at stacking defects are further observed in undoped InAs NWs by temperature-dependent measurements but are absent in Si-doped InAs NWs due to the increased Fermi energy.

THE INFLUENCE OF THE EXTREME ULTRAVIOLET SPECTRAL ENERGY DISTRIBUTION ON THE STRUCTURE AND COMPOSITION OF THE UPPER ATMOSPHERE OF EXOPLANETS

ABSTRACT By varying the profiles of stellar extreme ultraviolet (EUV) spectral energy distributions (SEDs), we tested the influences of stellar EUV SEDs on the physical and chemical properties of an escaping atmosphere. We apply our model to study four exoplanets: HD 189733b, HD 209458b, GJ 436b, and Kepler-11b. We find that the total mass loss rates of an exoplanet, which are determined mainly by the integrated fluxes, are moderately affected by the profiles of the EUV SED, but the composition and species distributions in the atmosphere can be dramatically modified by the different profiles of the EUV SED. For exoplanets with a high hydrodynamic escape parameter (λ), the amount of atomic hydrogen produced by photoionization at different altitudes can vary by one to two orders of magnitude with the variation of stellar EUV SEDs. The effect of photoionization of H is prominent when the EUV SED is dominated by the low-energy spectral region (400–900 Å), which pushes the transition of H/H+ to low altitudes. In contrast, the transition of H/H+ moves to higher altitudes when most photons are concentrated in the high-energy spectral region (50–400 Å). For exoplanets with a low λ, the lower temperatures of the atmosphere make many chemical reactions so important that photoionization alone can no longer determine the composition of the escaping atmosphere. For HD 189733b, it is possible to explain the time variability of Lyα between 2010 and 2011 by a change in the EUV SED of the host K-type star, yet invoking only thermal H i in the atmosphere.

Spectroscopic properties of the glass of fluoroaluminate systems with small additives of barium metaphosphate activated with the ions of rare-earth elements

Optical and EPR studies of fluoroaluminate glass based on usovite with small additives of barium metaphosphate (0.1–10 mol %) have been performed. The introduction of phosphates in the composition of the fluoride matrix of glass leads to a decrease in the crystallization ability but to the simultaneous shift of the edge of the transmission band into the high-energy spectral region. It was shown that for compositions with 1–2 mol % of barium metaphosphate this shift does not exceed 125 cm−1 at a transmission of not less than 60% to 1430 cm−1 (6.4 μm) for the samples with the thickness of 1 mm. It is supposed that glass containing 1.5–2.0 mol % Ba(PO3)2 is characterized by the mixed frame of glass different from the chain structure of fluoroaluminate and phosphate glass.

Influence of absorption saturation on the shape of CdSe absorption edge

Influence of light polarization on absorption saturation for wurtzite modification CdSe has been investigated. It has been ascertained that the size of blurring the fundamental absorption edge for wurtzite modification CdSe is determined by the non-equilibrium electron filling both the conduction band extremum, when the energy of photons h is higher than the bandgap energy Eg, and the density-of- state tail caused by the presence of static disorder, when the h < Eg. The density-of-state tail resulting from the presence of dynamic disorder is not filled with electrons because of continuous changes of the dynamic potential relief value in time. In the high-energy spectral region, change in the absorption coefficient is limited by the stimulated emission processes.

Temperature sensing with Eu3+ doped TiO2 nanoparticles

Luminescence temperature sensing with Eu3+ doped TiO2 nanoparticles was tested over a temperature range of 307–533K. Anatase Eu3+:TiO2 nanoparticles of 10–20nm in diameter are prepared using the hydrolytic sol–gel route. In photoluminescence emission spectra of Eu3+:TiO2 nanoparticles two distinct spectral regions are observed: the high energy spectral region associated with the trap emission of the TiO2 host, and the low energy spectral region with well resolved emission peaks of the Eu3+ ions. The ratio between Eu3+ emission and TiO2 trap emission, and the Eu3+ emission decay shows strong temperature dependence, and are tested for temperature sensing. It is found that relative sensor sensitivity ranges from 0.17 to 2.43%K−1 and is among the highest recorded for inorganic nanosensors. Temperature resolution is better than 1K over a wide temperature range and reaches 0.33K for decay measurements and 0.46K for the fluorescence intensity ratio measurements at about 400K.

Towards the understanding of the intentionally induced yellow luminescence in GaN nanowires

AbstractGallium nitride (GaN) has gained a lot of attention due to its high range of applications as solid state light emitters and detectors. However, the nitride samples often evidence deep level optically active defects affecting their performance on the high energy spectral region. This is the case for the commonly observed yellow luminescence (YL) band detected in bulk samples and thin films. Despite the large amount of literature reports on the processes that rule this emission in GaN films, there is still some controversy regarding the origin of the defects from where the YL originates. Furthermore, decreasing the dimensionality by analysing GaN nanowires provides new information on the luminescence behaviour when compared with epilayers. By using room temperature optical analysis, we aim to contribute to a deeper insight into the understanding of the YL detected in GaN NW, where YL was induced/enhanced by ion implantation and annealing treatments. YL was seen to be strongly dependent on different surface modifications, the analysis environment and illumination/irradiation excitation time. (© 2013 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Angular distribution of electrons in the field of a short laser pulse of relativistic intensity

Based on the dynamics of the electron in the field of a laser pulse of relativistic intensity, the electron emission angles with respect to the laser pulse propagation axis are calculated. The angular distribution of accelerated electrons is analyzed together with their energy spectrum. It is shown that fast electrons forming the high-energy spectral region are emitted into a fixed angular cone.

Enhanced light diffraction from self-assembled double-layer colloidal crystals

We demonstrate that double-layer colloidal photonic crystals function as wavelength- and polarization-insensitive blazed transmission gratings with efficiencies as high as 63% in the high-energy spectral region. This phenomenon, which is known as specular-resonance-enhanced diffraction, has been reported for a small-scale cluster of microspheres with a limited size parameter. By performing accurate characterization employing large-area colloidal crystal films self-assembled by an inclined dip-coating method with a controlled number of layers, this peculiar and efficient diffraction was demonstrated to be a universal property of double-layer colloidal crystal films.

Spectroscopic properties of neuroleptics: IR and Raman spectra of Risperidone (Risperdal) and of its mono- and di-protonated forms

Structures and IR and Raman spectra of Risperidone in its neutral, mono- and di-protonated forms were calculated in gas phase by DFT-B3LYP/6-31G* level. Mono-protonation occurs at the nitrogen atom of the piperidine ring, while nitrogen atom of the pyrimidine ring is the preferred site for the second protonation. The lowest-energy structure of the mono-protonated Risperidone is characterized by formation of a strong seven-membered O(pyrimidine ring)⋯ +H–N(piperidine ring) intramolecular hydrogen-bonded cycle. In the high-energy spectral region (3500–2500 cm −1), the bands of the N–H + stretches and the changes in wavenumbers and IR intensities of the C–H stretches near to the piperidine nitrogen atom (Bohlmann effect) are potentially useful to discriminate conformations and protonation states. Di-protonated structures can be identified by the presence of an isolated absorption peak located in the low-energy IR region (660–690 cm −1), attributed to the out-of-plane N–H +(pyrimidine ring) bending deformation. The most intense Raman band of neutral Risperidone placed at ca. 1500 cm −1, assigned to C C(pyrimidine ring) stretch + C N(pyrimidine ring) stretch, can be a useful vibrational marker to distinguish the neutral from the protonated forms.

Spectral shift of photoluminescence bands of the (SiC)1−x (AlN)x epitaxial films due to laser annealing

The effect of laser annealing on the photoluminescence properties of (SiC)1−x (AlN)x epitaxial films was studied. It was proposed that annealing causes the displacement of the Al and N atoms from their lattice sites and the formation of AlSi-NC donor-acceptor pairs acting as the luminescence centers. According to this model, the increase in the annealing time is accompanied by the formation of donor-acceptor pairs with the shortest interatomic distances at the expense of associations of the distant defects and by a shift of the respective photoluminescence band to the high-energy spectral region.

Use of a Toroidal Mirror in the Soft X-Ray Optical System

A toroidal mirror has been produced and used as a prereflector in the optical system of the soft X-ray spectroscopy. The mirror reduces the astigmatism inherent in a grazing-incidence monochromator and the intensity of radiation available for experiments is appreciably increased. Undesirable higher order radiation which appears in the first order spectrum is found to be efficiently removed when the mirror is used in the high energy spectral region. Critical cut-off wavelength in a few materials is discussed.