Search results for "absorption."

Generation and excitation of point defects in silica by synchrotron radiation above the absorption edge

2010

We report photoluminescence measurements carried out on amorphous SiO{sub 2} upon excitation by synchrotron light. Exposure of the as-grown material to above-edge light at low temperature induces the formation of nonbridging oxygen hole centers (NBOHC), localized in a thin layer below the surface limited by the penetration depth (tens of nm) of impinging light. After concluding the exposure to 11 eV light, stable defects are revealed by observing their characteristic 1.9 eV photoemission band excited at 4. 8eV. The local concentration of induced defects, supposedly formed by nonradiative decay of excitons, is very high (close to approx10{sup 21} cm{sup -3}) and independent of the previous h…

Experimental study of 100Tc β decay with total absorption γ -ray spectroscopy

2017

The β decay of 100Tc has been studied by using the total absorption γ -ray spectroscopy technique at the Ion Guide Isotope Separator On-Line facility in Jyväskylä. In this work the new Decay Total Absorption γ -ray Spectrometer in coincidence with a cylindrical plastic β detector has been employed. The β intensity to the ground state obtained from the analysis is in good agreement with previous high-resolution measurements. However, differences in the feeding to the first-excited state as well as weak feeding to a new level at high excitation energy have been deduced from this experiment. Theoretical calculations performed in the quasiparticle random-phase approximation framework are also r…

Application of algae in active biomonitoring of the selected holding reservoirs in swietokrzyskie province

2016

Abstract During the years 2014-2015, biomonitoring studies were carried out at three holding reservoirs located in Swietokrzyskie Province (central Poland): Kielce artificial lake, Chancza reservoir and Sielpia reservoir. In sea water algae Palmaria palmata (Linnaeus) Weber & Mohr, exposed in the analysed waters, the increases of concentrations were determined by the atomic absorption spectrometry method (AAS), of the following: Mn, Fe, Cu, Zn, Cd and Pb. Conductivity and pH were also determined in the reservoirs waters. The differences between the increases of heavy metal concentrations in the samples of algae found along the coastline were indicated; they result from different distanc…

<title>Electro-optical and fluorescence lifetime studies of aminophthalimide probes in liquids</title>

1995

The modified electro-optical absorption and emission methods are described as well as their use for measurements of electrical dipole moments of five aminophthalimides in ground and excited states. It is found that there exists a principal difference between properties of 3- aminophthalimide (3AP) and 4-amino-N-methylphthalimide (4ANMP) in different solvents. The equilibrated dipole moment of 3AP in its excited state is practically independent on the solvent polarity, in comparison with 4ANMP. The possible mechanism of this effect is discussed.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Huge shift of fundamental electronic absorption edge in Sr1−xBaxNb2O6 crystals at elevated temperatures

1995

Light-Scattering and -Absorption of Nanoparticles

2012

To understand the optical response of nanoparticles to the incident light, a theoretical description is needed, which is given in this chapter. In a first approximation, these optical properties can be described using a quasi-static model, which assumes a particle-size much smaller than the wavelength of the light. The derivation of the polarizability of a sphere, which describes its optical properties, and further extensions for spheroidal, rod-shaped and coated particles are given in Sect. 2.2.

Hole burning and pressure phenomena in chromoproteins

1993

Abstract We investigated the behavior of spectral holes under pressure at various frequencies within the inhomogeneous band for two proteins, namely myoglobin and horseradish peroxidase. In order to achieve narrow bandwidth hole burning, the heme chromophore was replaced by protoporphyrin IX and mesoporphyrin IX, respectively. In myoglobin, we found that the pressure induced shift of the holes varied in a strongly non-linear fashion, when the burn-frequency was tuned across the absorption band. In horseradish peroxidase the pressure shift was linear with burn-frequency but changed in a dramatic fashion upon complex formation with a substrate molecule. These observations are interpreted with…

An ab initio study of the low-lying 1 A′ electronic states of indene

1999

Abstract The electronic absorption spectrum of indene in the region of the lowest-lying valence π → π * singlet excited states was studied using multi-configurational second-order perturbation theory through the CASPT2 formalism. Four 1 A′ states were found to be the most important for describing the excitation spectrum up to 6.8 eV. Their transition energies (oscillator strengths in parentheses) were computed to be: 4.46 eV (0.0004), 5.02 eV (0.175), 6.14 eV (0.221), and 6.36 eV (0.434). These states can be labelled and described as the four Platt states of indene: 1 L a , 1 L b , 1 B b , and 1 B a , respectively. This description of the spectrum explains the experimental observations bett…

Primary production calculations for sea ice from bio-optical observations in the Baltic Sea

2016

Abstract Bio-optics is a powerful approach for estimating photosynthesis rates, but has seldom been applied to sea ice, where measuring photosynthesis is a challenge. We measured absorption coefficients of chromophoric dissolved organic matter (CDOM), algae, and non-algal particles along with solar radiation, albedo and transmittance at four sea-ice stations in the Gulf of Finland, Baltic Sea. This unique compilation of optical and biological data for Baltic Sea ice was used to build a radiative transfer model describing the light field and the light absorption by algae in 1-cm increments. The maximum quantum yields and photoadaptation of photosynthesis were determined from 14C-incorporatio…

Phase transition of tetragonal copper sulfide Cu2S at low temperatures

2017

The low-temperature behavior of tetragonal copper sulfide, ${\mathrm{Cu}}_{2}\mathrm{S}$, was investigated by powder and single-crystal x-ray diffraction, calorimetry, electrical resistance measurements, and ambient temperature optical absorption spectroscopy. The experiments were complemented by density-functional-theory-based calculations. High-quality, polycrystalline samples and single crystals of tetragonal copper sulfide were synthesized at 5 GPa and 700 K in a large volume multianvil press. Tetragonal ${\mathrm{Cu}}_{2}\mathrm{S}$ undergoes a temperature-induced phase transition to an orthorhombic structure at around 202 K with a hysteresis of $\ifmmode\pm\else\textpm\fi{}21$ K, an e…