Search results for "absorption."
showing 10 items of 2682 documents
Effect of Halogen Ions on the Photocycle of Fluorescent Carbon Nanodots
2019
Carbon dots (C-dots) are well-known for their strong sensitivity to the environment, which reflects on intensity and shape changes of their fluorescence, induced by various interacting ions and molecules in solution. Although these interactions have been extensively studied in the last few years, especially in view of their possible sensing applications, the existing works have mostly focused on the quenching of C-dot fluorescence induced by metal cations. In fact, these latter easily bind to C-dots surfaces, which are negatively charged in most cases, promoting an electron transfer from the surface to them. Much less is known from the literature on the effect induced on C-dots by prototypi…
Reddening map around ? Orionis
1990
uvbyβ photometry has been done for early-type stars in the surroundings of the shell star α Ori. The reddening maps show the presence of irregularly distributed absorbing material.
A comprehensive analysis of the cool RCB star DY Persei
2007
Context. Theoretically, the number of cool Galactic R Coronae Borealis stars (RCBs) should be greater than the warm RCBs, however to date, only a few candidates have been detected. Aims. Observations of the extremely cool RCB candidate, DY Per, and the anonymous nearby star (the “Taipei star”) are presented to specify its fundamental parameters and evolutionary status. Methods. CCD BVRI photometry and low-resolution spectroscopy at deep light decline was carried out in 2004. A high-resolution spectrum was gathered near the maximum light in 2002, and a qualitative analysis was made relative to the typical carbon stars of various types. Results. Near the light maximums, the nearby anonymous s…
Photomicrography of skin by ultraviolet light.
1971
Skin sections superimposed on fine-grained photographic plates were exposed to ultraviolet light (2580 A wavelength). The images obtained, which reproduced the microanatomy of tissue in the process of ultraviolet photoabsorption, were studied under the microscope. Since absorption is proportional to the concentration of such biologically important chromophore-bearing substances as nueleoproteins and melanoproteins, the method gives information on the content and distribution of these substances in normal and altered tissue.
Transmission of light in deep sea water at the site of the Antares neutrino telescope
2005
The ANTARES neutrino telescope is a large photomultiplier array designed to detect neutrino-induced upward-going muons by their Cherenkov radiation. Understanding the absorption and scattering of light in the deep Mediterranean is fundamental to optimising the design and performance of the detector. This paper presents measurements of blue and UV light transmission at the ANTARES site taken between 1997 and 2000. The derived values for the scattering length and the angular distribution of particulate scattering were found to be highly correlated, and results are therefore presented in terms of an absorption length lambda_abs and an effective scattering length lambda_sct^eff. The values for …
Post UV irradiation annealing of E’ centers in silica controlled by H2 diffusion
2004
Abstract We investigate the isothermal annealing of E′ centers generated by UV photons (266 nm) of a pulsed Nd:YAG laser in two natural silica types differing for their OH content. Electron spin resonance and absorption spectra recorded at room temperature at different delays from the laser exposure evidenced a partial reduction of E′ centers, more pronounced in the wet silica. These post irradiation kinetics complete within 10 5 s, regardless the silica type, and they are consistent with a diffusion limited reaction between the E′ centers and the molecular hydrogen H 2 . Analysis of our data is done by theoretical fits using the Waite's equation and compared with the H 2 diffusion paramete…
Modification of vacuum-ultraviolet absorption of SiOH groups in SiO2 glass with temperature, F2 laser irradiation, and H–D isotope exchange
2006
Abstract Variations of vacuum-ultraviolet (VUV) absorption of silanol (SiOH) groups in synthetic wet SiO 2 glass with temperature, exposure to F 2 laser light, and with H–D isotope exchange were examined at photon energies below 8 eV. The intensity of the VUV absorption band decreases with cooling or with exposure to F 2 laser light. The spectral changes in both cases are qualitatively similar and are attributed to an alternation of the bonding configuration of SiOH groups from isolated into hydrogen-bonded states. However, the resultant states are distinctly different: the hydrogen-bonded state formed on cooling is restored reversibly to the isolated state on heating, while that induced by…
QUADRUPOLAR CHARACTER OF THE Ti K-EDGE PREPEAKS IN TiO2 BY RESONANT AUGER
2002
Resonant spectroscopies offer a new opportunity to get more insight into excited electronic states by studying line shapes and intensities of decay processes. For photon excitations in the pre-K-edge region, the Ti KL 2,3 L 2,3 Auger spectra in TiO 2 show additional peaks when an electron is promoted in localized d-like states via a quadrupolar transition. This resonant process is used to unravel the respective contributions of quadrupolar and dipolar transitions to the absorption edge prepeaks.
Characterisation of structured thin films made from complex materials by photoabsorption spectromicroscopy
1998
Al3 and YBa2Cu3O7/PrBa2Cu3O7. To investigate devices built from these complex materials we applied element-sensitive photoemission electron microscopy (PEEM). Information about the chemical composition of the imaged sample can be obtained by PEEM via tuning the photon energy to X-ray absorption edges. To apply spectromicroscopy we acquired microscopic images using photon energies near and at the edges. Such images give the lateral distribution of a specific element. Microspectroscopy is performed by recording the intensity of the true secondary electrons in selected spots during a sweep of the photon energy. The main aim of our work was to observe oxygen-related defects and changes in the c…
Photoabsorption and MXCD in Photoemission Microscopy for Characterization of Advanced Materials
1999
We used imaging spectromicroscopy to characterise micro-patterned thin films of magnetic materials like FeNi alloys on Silicon. To investigate devices built from complex materials we applied element-sensitive photoelectron emission microscopy (PEEM). Information about the chemical composition of the imaged sample can be obtained by PEEM via tuning the photon energy to X-ray absorption edges. One aim of our work was to observe oxygen related defects and changes in the composition effecting the physical properties of the materials. The use of circularly polarised photons allows us to image magnetic domains by making use of the magnetic circular dichroism (MXCD).