Search results for "Absorption"
showing 10 items of 2701 documents
EXAFS study of mixed nickel molybdenum oxide thin films at the Ni and Mo K-edges
2004
Mixed nickel molybdenum oxide thin films were produced by DC magnetron co-sputtering technique with the nickel content about 8, 16 and 25 at%. X-ray absorption spectroscopy at the Ni and Mo K-edges was used to study the local atomic structure in the films. The best-fit analysis of the EXAFS signals suggests that (i) the films are amorphous, except for the highest nickel content (25 at%), at which a segregation of NiO phase was observed; (ii) nickel and molybdenum atoms are octahedrally coordinated by oxygen atoms. Opposite to the NiO6 octahedra, the MoO6 octahedra are strongly distorted, that results in an existence of two groups of oxygen atoms—four nearest at B1.76 ( A and two distant at …
Transient absorption of polarons in KNbO3
2002
Abstract Transient absorption spectra have been measured in a number of undoped KNbO 3 crystals following two kinds of electronic excitation: two-photon absorption of 200 fs laser pulses and 10 ns pulsed electron beam. A band peaking at 0.8 eV and broad, poorly resolved absorption in the range 1.3–3.3 eV were observed. Based on similarity to the 1 eV band in LiNbO 3 previously identified as the intrinsic electron polaron (electron self-localized on niobium in the regular lattice site), we suggest that the transient absorption band at 0.8 eV in KNbO 3 is also associated with the intrinsic electron polaron.
Diagnostic Potential of Cosmic-Neutrino Absorption Spectroscopy
2004
Annihilation of extremely energetic cosmic neutrinos on the relic-neutrino background can give rise to absorption lines at energies corresponding to formation of the electroweak gauge boson $Z^{0}$. The positions of the absorption dips are set by the masses of the relic neutrinos. Suitably intense sources of extremely energetic ($10^{21}$ -- $10^{25}$-eV) cosmic neutrinos might therefore enable the determination of the absolute neutrino masses and the flavor composition of the mass eigenstates. Several factors--other than neutrino mass and composition--distort the absorption lines, however. We analyze the influence of the time-evolution of the relic-neutrino density and the consequences of …
Improving the Performance of Quasi-Hemispherical CdZnTe Detectors Using Infrared Stimulation
2012
The influence of monochromatic optical stimulation with wavelengths from 400 to 1100 nm on the characteristics of CdZnTe quasi-hemispherical detectors was studied. It was found that illumination with infrared (IR) light with wavelengths of 870-900 nm close to the absorption edge of the CdZnTe significantly improves the performance of the detector at room temperature. Improvement can be achieved with low-intensity IR illumination at 1-300 μW depending on the chosen wavelength of illumination. Higher intensity illumination was observed to lead to the degradation of the detector's spectrometric characteristics. IR radiation was noted to influence the detector's sensitivity, changing the equili…
Shapes ofPb192,190ground states fromβ-decay studies using the total-absorption technique
2015
The beta decay of Pb-192,Pb-190 has been studied using the total absorption technique at the ISOLDE (CERN) facility. The beta-decay strength deduced from the measurements, combined with QRPA theoretical calculations, allow us to infer that the ground states of the Pb-192,Pb-190 isotopes are spherical. These results represent the first application of the shape determination method using the total absorption technique for heavy nuclei and in a region where there is considerable interest in nuclear shapes and shape effects.
Deformation of Sr and Rb isotopes close to theN=Zline viaβ-decay studies using the total absorption technique
2013
A study of the Gamow-Teller strength distributions $B$(GT) in the beta decay of ${}^{78}$Sr and ${}^{76,78}$Rb has been made using a total absorption spectrometer (TAS). Following the success in deducing the sign of the deformation for ${}^{76}$Sr, a similar approach is adopted for ${}^{78}$Sr based on a comparison of the measured $B$(GT) with quasiparticle random-phase approximation calculations. This work confirms its previously expected prolate deformation in the ground state. Conclusions about the structure of the odd-odd ${}^{76,78}$Rb isotopes have been drawn based on their measured $B$(GT) distributions.
Absorber materials for low-energy neutrons—Theoretical and experimental studies
2012
Abstract Absorber materials for low-energy neutrons are studied in the theoretical framework of quantum mechanics with a complex potential. Analytical expressions and numerical calculations of the neutron reflectivity for perpendicular and isotropic motion towards a surface for four different material classes are presented. Comparative experimental studies of four absorber materials have been carried out: Polyethylene, titanium, boron-10 and lithium stearate. In a quasi-storage experiment with ultracold neutrons the latter material features the highest absorption property.
Measuring the phi meson width in the medium from p induced phi production in nuclei
2004
We study the $A$ dependence of the $\phi$ meson production cross section in proton nucleus reactios at energies just above threshold, which are accessible in an experimental facility like COSY. This $A$ dependence has two sources: the distortion of the incident proton and the absorption of the $\phi$ in its way out of the nucleus. This second process reduces the cross section in about a factor two in heavy nuclei. Thus we show that the $A$ dependence of the cross section contains valuable information on the $\phi$ width in the nuclear medium.
Structure functions from the NMC
1992
The New Muon Collaboration has measured deep inelastic muon scattering on hydrogen and deuterium at incident energies of 90 and 280 GeV. From the measured cross section ratios σd/σp the difference of R, the ratio of longitudinally to transversely polarised virtual photon absorption cross sections, was obtained. Covering a range in x from 0.01 to 0.3 at a typical Q2 of 9 GeV2 the results are compatible with zero. The structure functions F2p and F2d were extracted in a wide kinematic range: 0.006 1 GeV2. Extrapolation to small χ of recent parton distributions are shown to disagree with the NMC results.
Characterization of deuteride titanium targets used in neutron generators
2000
Abstract The study of the physicochemical characteristics of titanium thin films and the corresponding deuterium absorption/desorption kinetics was performed. In order to optimize the production of high-energy neutrons the behaviour of deuteride titanium targets has been studied experimentally by bombardment with 120 and 350 kV deuterons by means of electrostatic accelerators. The importance of the deposit evaporation conditions on the efficiency of neutron emission is clearly demonstrated as well as the thermomechanical stability of the Ti thin film by deuteron bombardment. The main parameters involved in the targets behaviour have been discussed from a thermodynamical approach.