Search results for " Paramagnetic resonance"
showing 10 items of 567 documents
Alpha and deuteron irradiation effects on silica nanoparticles
2014
We present an experimental investigation focused on the effects of alpha and deuteron irradiation on different silica nanoparticles. The study has been devoted also to characterize the induced point defects and the eventual structural modifications to evaluate the effects of the different irradiation source in comparison with the bulk materials. After irradiation up to about 10^16 ions cm^-2, we performed electron paramagnetic resonance (EPR), photoluminescence (PL), infrared (IR) absorption, Raman, and atomic force microscopy (AFM) measurements. We found that the two types of irradiation qualitatively induce comparable effects. Furthermore, irradiation generates the socalled twofold coordi…
Optical properties of phosphorous-related point defects in silica fiber preforms
2009
Physical review / B 80, 205208 (2009). doi:10.1103/PhysRevB.80.205208
Twofold coordinated Ge defects induced by gamma-ray irradiation in Ge-doped SiO2
2008
We report an experimental study by photoluminescence, optical absorption and Electron Paramagnetic Resonance measurements on the effects of exposure of Ge-doped amorphous SiO2 to gamma ray radiation at room temperature. We have evidenced that irradiation at doses of the order of 1 MGy is able to generate Ge-related defects, recognizable from their optical properties as twofold coordinated Ge centers. Until now, such centers, responsible for photosensitivity of Ge-doped SiO2, have been induced only in synthesis procedures of materials. The found result evidences a role played by gamma radiation in generating photosensitive defects and could furnish a novel basis for photosensitive pattern wr…
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…
Power saturation of ESR signal in ammonium tartrate exposed to 60Co gamma-ray photons, electrons and protons.
2006
Abstract Marrale, M., Brai, M., Triolo, A., Bartolotta, A. and D'Oca, M. C. Power Saturation of ESR Signal in Ammonium Tartrate Exposed to 60Co γ-Ray Photons, Electrons and Protons. Radiat. Res. 166, 802–809 (2006). In this paper we present an investigation of the electron spin resonance (ESR) line shape of ammonium tartrate (AT) dosimeters exposed to radiation with different linear energy transfer (LET). We exposed our dosimeters to γ-ray photons (60Co), 7 MeV and 14 MeV initial energy electrons, and 19.3 MeV initial energy protons. The differences in the power saturation behavior of ESR spectra of AT irradiated with photons, electrons and protons could be correlated to the effective LET o…
Photoelectrical detection of electron spin resonance of nitrogen-vacancy centres in diamond
2015
The protocols for the control and readout of Nitrogen Vacancy (NV) centres electron spins in diamond offer an advanced platform for quantum computation, metrology and sensing. These protocols are based on the optical readout of photons emitted from NV centres, which process is limited by the yield of photons collection. Here we report on a novel principle for the detection of NV centres magnetic resonance in diamond by directly monitoring spin-preserving electron transitions through measurement of NV centre related photocurrent. The demonstrated direct detection technique offers a sensitive way for the readout of diamond NV sensors and diamond quantum devices on diamond chips. The Photocurr…
Characterization ofE′δand triplet point defects in oxygen-deficient amorphous silicon dioxide
2006
We report an experimental study by electron paramagnetic resonance (EPR) of $\ensuremath{\gamma}$-ray irradiation induced point defects in oxygen deficient amorphous $\mathrm{Si}{\mathrm{O}}_{2}$ materials. We have found that three intrinsic ($\mathrm{E}^{\ensuremath{'}}{}_{\ensuremath{\gamma}}$, $\mathrm{E}^{\ensuremath{'}}{}_{\ensuremath{\delta}}$, and triplet) and one extrinsic $({[\mathrm{Al}{\mathrm{O}}_{4}]}^{0})$ paramagnetic centers are induced. All the paramagnetic defects but $\mathrm{E}^{\ensuremath{'}}{}_{\ensuremath{\gamma}}$ center are found to reach a concentration limit value for doses above ${10}^{3}\phantom{\rule{0.3em}{0ex}}\mathrm{kGy}$, suggesting a generation process f…
Strong reduction of the Korringa relaxation in the spin-density wave regime ofEuFe2As2observed by electron spin resonance
2010
Electron spin resonance measurements in ${\text{EuFe}}_{2}{\text{As}}_{2}$ single crystals revealed an absorption spectrum of a single resonance with Dysonian line shape. Above the spin-density wave (SDW) transition at ${T}_{\text{SDW}}=190\text{ }\text{K}$ the spectra are isotropic and the Eu spins relax via the conduction electrons resulting in a Korringa-type increase in the linewidth. Below ${T}_{\text{SDW}}$, a distinct anisotropy develops and the relaxation behavior of the Eu spins changes drastically into one with characteristic properties of a magnetic insulating system, where dipolar and crystal-field interactions dominate. This indicates a spatial confinement of the conduction ele…
Instantaneous diffusion in spin-echo dynamics: A frequency-domain experimental investigation.
1992
We report an experimental investigation on the spectral content of the echo radiation emitted by an electron spin system excited by a two-pulse sequence. The measurements are carried out at liquid-helium temperature in a sample of quartz containing a very low concentration of [${\mathrm{AlO}}_{4}$${]}^{0}$ centers, in which instantaneous diffusion mechanism makes the main contribution to the phase relaxation. The experimental spectral shapes reproduce the theoretical ones, as calculated for an ideal system of noninteracting spins. However, the agreement is only qualitative, as the experimental spectral widths are found to be less than expected by a factor that depends on the exciting sequen…
Electron paramagnetic resonance study of theCe3+pair centers inYAlO3:Ce scintillator crystals
2015
Single crystals of $\mathrm{YAl}{\mathrm{O}}_{3}$ doped with Ce have been studied by electron paramagnetic resonance (EPR) at the 9.4 and 34 GHz microwave bands. Besides the single-ion $\mathrm{C}{\mathrm{e}}^{3+}$ spectrum, measurements have revealed many satellite lines which belong to the $\mathrm{C}{\mathrm{e}}^{3+}\text{\ensuremath{-}}\mathrm{C}{\mathrm{e}}^{3+}$ pair centers. Their spectra have been fitted by a general effective spin Hamiltonian describing two interacting particles with the spin $S=1/2$. Corresponding $g$ factors and spin-spin coupling constants have been determined. The spin-spin coupling constants are in the range from 0.1 up to $0.65\phantom{\rule{0.16em}{0ex}}\mat…