Radiation Damage Centers Research Articles

Electron paramagnetic resonance study of the paramagnetic centers in gamma-irradiated 4-Nitrobenzaldehyde single crystal

4-Nitrobenzaldehyde (C7H5NO3) (4NB) single crystals were obtained by slow evaporation technique. Single crystals were made paramagnetic by irradiation with a 60Co-gamma rays. Electron Paramagnetic Resonance (EPR) Spectroscopy method was used to detect the radiation damage center formed in the single crystals. As a result of temperature scanning of EPR spectra at different temperatures between 120 and 470 K, it was found to be independent of temperature. That's why the EPR study was done only at 300 K. The radiation effect caused the formation of the 4NB anion radical in the 4NB single crystal. All the protons in the structure created hyperfine structure splittings. The principal values of the hyperfine structure constants resulting from the interaction of the unpaired electron with protons, the principal values of the g-tensor and their direction cosines were calculated.

Electron paramagnetic resonance study of gamma-irradiated soduxin single crystal

Single crystals of soduxin were 60Co-gamma irradiated at room temperature. The irradiated single crystals were studied at 120 K using Electron Paramagnetic Resonance (EPR) spectroscopy. The investigation of EPR spectra of irradiated single crystals of soduxin showed the presence of two soduxin anion radicals. The g values of the radiation damage centers observed in soduxin single crystal and the hyperfine structure constants of the free electron with nearby protons were obtained. Highlights Soduxin single crystal was irradiated with gamma rays. Paramagnetic centers in soduxin single crystal were investigated. Two carbon-centered radicals with the same structure were detected. EPR parameters changed anisotropically.

Detection of Single W-Centers in Silicon

Controlling the quantum properties of individual fluorescent defects in silicon is a key challenge towards advanced quantum photonic devices prone to scalability. Research efforts have so far focused on extrinsic defects based on impurities incorporated inside the silicon lattice. Here we demonstrate the detection of single intrinsic defects in silicon, which are linked to a tri-interstitial complex called W-center, with a zero-phonon line at 1.218${\mu}$m. Investigating their single-photon emission properties reveals new information about this common radiation damage center, such as its dipolar orientation and its photophysics. We also identify its microscopic structure and show that although this defect does not feature electronic states in the bandgap, Coulomb interactions lead to excitonic radiative recombination below the silicon bandgap. These results could set the stage for numerous quantum perspectives based on intrinsic luminescent defects in silicon, such as quantum integrated photonics, quantum communications and quantum sensing.

Electron Paramagnetic Resonance Study of the Radiation Damage Centers in Menadione Single Crystal

The radiation damage centers in the 60Co- rays irradiated menadione (2-methyl-1,4-naphthoquinone; Vitamin K3; C11H8O2 ) single crystals were examined at 120 K by Electron Paramagnetic Resonance (EPR) spectroscopy. The presence of two radicals was detected in the compound. Both radicals are carbon centered radicals. Analysis of the EPR spectra of gamma-irradiated menadione single crystals along three different axes showed that the C(11)-H(19) bond of the compound was broken. It was determined that the unpaired electron located on the C(11) atom. The g values and the hyperfine structure constants of the radiation damage centers observed in menadione single crystal were obtained. Accuracy of experimental data was observed by simulation study.

Generating T centres in photonic silicon-on-insulator material by ion implantation

Global quantum networks will benefit from the reliable fabrication and control of high-performance solid-state telecom photon-spin interfaces. T radiation damage centres in silicon provide a promising photon-spin interface due to their narrow O-band optical transition near 1326 nm and long-lived electron and nuclear spin lifetimes. To date, these defect centres have only been studied as ensembles in bulk silicon. Here, we fabricate high concentration T centre ensembles in the 220 nm device layer of silicon-on-insulator wafers by ion implantation and subsequent annealing. We then develop a method that uses spin-dependent optical transitions to benchmark the characteristic optical spectral diffusion within these T centre ensembles. Using this new technique, we show that with minimal optimization to the fabrication process high densities of implanted T centres localized ≲100 nm from an interface display ∼1 GHz characteristic levels of total spectral diffusion.

Electron paramagnetic resonance study of the paramagnetic centers in gamma-irradiated oxalic acid dihydrate single crystal

The Electron Paramagnetic Resonance (EPR) spectra of the radicals produced by γ-irradiation of a single crystal of oxalic acid dihydrate (C2H6O6) have been reported. The EPR spectra of gamma-irradiated single crystals of oxalic acid dihydrate have been studied for different orientations of crystals in a magnetic field. As a result of studies carried out along three axes, it has been determined that there are two biradicals. The EPR spectra have been investigated at temperatures between 125 and 450 K. The spectra have been found to be temperature independent. The g values of the radiation damage centers observed in oxalic acid dihydrate acid single crystal and the hyperfine structure constants of the free electron with nearby protons have been obtained from the single crystal EPR analysis.

Electron paramagnetic resonance study of the paramagnetic center in gamma-irradiated tetrahydrophthalic anhydride single crystal

Electron Paramagnetic Resonance (EPR) analysis of gamma-irradiated tetrahydrophthalic anhydride (C8H8O3) single crystals was performed at 120 K. The single crystals were exposed to 60Co-gamma source at room temperature. The EPR spectra of gamma-irradiated single crystals of tetrahydrophthalic anhydride (THPA) were recorded at 10-degree intervals for different orientations of crystals in a magnetic field. Detailed examination of THPA single crystals by EPR spectroscopy method showed the presence of two carbon-centered THPA anion radicals. Both radicals were determined to have the same structure. The anion radicals observed in gamma-irradiated THPA single crystal were created by the scission of the carbon–oxygen double bond. The g values of the radiation damage centers observed in the THPA single crystal and the hyperfine structure constants of the free electron with nearby protons were obtained. Highlights Single crystals of tetrahydrophthalic anhydride were exposed to gamma radiation. Radiation damage centers in single crystals of tetrahydrophthalic anhydride were determined by EPR spectroscopy method. The presence of two anion radicals in single crystals of tetrahydrophthalic anhydride was determined. The formation mechanism of the paramagnetic centers in the tetrahydrophthalic anhydride is similar to that of succinic anhydride.

Highly enriched Si28 reveals remarkable optical linewidths and fine structure for well-known damage centers

Luminescence and optical absorption due to radiation damage centers in silicon has been studied exhaustively for decades, but is receiving new interest for applications as emitters for integrated silicon photonic technologies. While a variety of other optical transitions have been found to be much sharper in enriched $^{28}$Si than in natural Si, due to the elimination of inhomogeneous isotopic broadening, this has not yet been investigated for radiation damage centers. We report results for the well-known G, W and C damage centers in highly enriched $^{28}$Si, with optical linewidth improvements in some cases of over two orders of magnitude, revealing previously hidden fine structure in the G center emission and absorption. These results have direct implications for the linewidths to be expected from single center emission, even in natural Si, and for models for the G center structure. The advantages of $^{28}$Si can be readily extended to the study of other radiation damage centers in Si.

Electron paramagnetic resonance study of the radiation damage in phosphoryethanolamine single crystal

Gamma irradiated phosphoryethanolamine (C2H8NO4P) single crystals were investigated at 140 K using Electron Paramagnetic Resonance (EPR) technique. Phosphoryethanolamine single crystals have been irradiated with 60Co-γ rays, at room temperature. The electron paramagnetic resonance (EPR) spectra of gamma irradiated phosphoryethanolamine single crystals have been studied for different orientations of crystals in a magnetic field. The spectra have been found to be temperature independent. The structure of the radical produced by γ-irradiation of a single crystal of phosphoryethanolamine was discussed. The investigation of EPR spectra of gamma-irradiated single crystals of phosphoryethanolamine showed the presence of two radicals. One of the radicals is the H2PO4˙ neutral radical formed by the breakdown of the O(7)C(8) bond. The other is the HPO4−˙ anion radical formed by cleavage of the O(7)C(8) bond and the attachment of an electron to O(2) by breaking H(1) bound to O(2). The principal values of the hyperfine coupling tensor of the unpaired electron and the principal values of the g-tensor and direction cosines of the radiation damage centers have been determined. The results were found to be in good agreement with the existing literature.

EPR investigation of damage centers formed in some drug powders irradiated with gamma rays

The radiation damage centers in levetiracetam, progesterone, ethosuximide, and propranolol hydrochloride were investigated by EPR spectroscopy at 295 K. The paramagnetic species were attributed to the -ĊHCHNH-, -CH2ĊH2CH- and -ĊH-, -ĊHCH2N- and-ĊH-, and -NĊCH2- radicals, respectively. The results were observed as being in good conformity with the literature. The spectra of these compounds were computer simulated. Furthermore, the EPR parameters of the radicals formed by ɣ-irradiation in the samples were determined.

EPR study of free radical in gamma-irradiated bis(cyclopentadienyl)zirconium dichloride single crystal

ABSTRACTBis(cyclopentadienyl)zirconium dichloride (BCZD; zirconocene dichloride) single crystals were exposed to 60Co-γ irradiation at room temperature. The irradiated single crystals were investigated between 125 and 470 K by electron paramagnetic resonance spectroscopy. The spectra of the crystals were found to be temperature independent. The paramagnetic center was attributed to the cyclopentadienyl radical. The g values of the radiation damage center observed in BCZD single crystal and the hyperfine structure constants of the free electron with nearby protons were obtained.

Electron paramagnetic resonance study of radiation-induced paramagnetic centers in succinic anhydride single crystal

Succinic anhydride single crystals were exposed to 60Co-gamma irradiation at room temperature. The irradiated single crystals were investigated at 125 K by Electron Paramagnetic Resonance (EPR) Spectroscopy. The investigation of EPR spectra of irradiated single crystals of succinic anhydride showed the presence of two succinic anhydride anion radicals. The anion radicals observed in gamma-irradiated succinic anhydride single crystal were created by the scission of the carbon-oxygen double bond. The structure of EPR spectra demonstrated that the hyperfine splittings arise from the same radical species. The reduction of succinic anhydride was identified which is formed by the addition of an electron to oxygen of the CO bond. The g values, the hyperfine structure constants and direction cosines of the radiation damage centers observed in succinic anhydride single crystal were obtained.

EPR study of radiation damage in gamma-irradiated 3-nitroacetophenone single crystal

ABSTRACTThis paper presents the results of the electron paramagnetic resonance (EPR) study of the anion radical formed from 3-nitroacetophenone (C8H7NO3) (3NAP) single crystal, by gamma irradiation. The EPR spectra of gamma-irradiated single crystals of 3NAP have been recorded at 10-degree intervals for different orientations of crystals in a magnetic field, at room temperature. The EPR analysis of gamma-irradiated crystals of 3NAP has shown that the radiation damage center produced by gamma irradiation is the carbon-centered 3NAP anion radical. One-electron reduction of 3NAP results in general bond loosening. The single crystals have been investigated between 120 and 450 K. The spectra have been found to be temperature-dependent. The EPR parameters of the 3NAP anion radical have been evaluated.

Electron paramagnetic resonance study of gamma-irradiated potassium hydroquinone monosulfonate single crystal

ABSTRACTGamma-irradiated potassium hydroquinone monosulfonate (PHM) single crystals were investigated between 125 and 300 K using the electron paramagnetic resonance (EPR) technique. Between 125 and 300 K no changes in the spectra have taken place. The spectra were found to be temperature independent. The investigation of EPR spectra of irradiated single crystals of PHM showed the presence of two PHM anion radicals. The g values of the radiation damage centers observed in the PHM single crystal and the hyperfine structure constants of the free electron with nearby protons were obtained.

EPR study of γ-irradiated cholesteryl methyl carbonate

The electron paramagnetic resonance (EPR) of γ-irradiated single crystals of cholesteryl methyl carbonate (C29H48O3) has been studied for different orientations of the crystals in a magnetic field. EPR spectra of cholesteryl methyl carbonate (C29H48O3irradiated by 60Co-γ were recorded between 125K and 300K for different orientations of the crystal in the magnetic field. The spectra were found to be temperature independent. In C29H48O3 single crystal, the radiation damage centers caused by a 60Co-γ source were determined as CḢ3CH2CH radical. For CḢ3CH2CH radical, a value of spectroscopic splitting factor g was calculated and experimentally results were supported by simulation program (WinEPR).

Electron paramagnetic resonance study of radiation damage in isonipecotic acid single crystal

The electron spin resonance spectra of the radical produced by gamma-irradiation of a single crystal of isonipecotic acid (piperidine-4-carboxylic acid) were reported, and the structure of the radical was discussed. Isonipecotic acid single crystals were exposed to 60Co-gamma irradiation at room temperature. The irradiated single crystals were investigated by Electron Paramagnetic Resonance (EPR) Spectroscopy between 115K and 300K. The spectra were found to be temperature independent. The g values of the radiation damage center observed in isonipecotic acid single crystal and the hyperfine structure constants of the free electron with nearby protons were obtained.

EPR Study of Gamma Irradiated Cholestanone Single Crystal

Cholestanone (C27H46O) single crystals were irradiated with Co-γ rays at room temperature. The spectra were recorded for di erent orientations of the crystal in the magnetic eld at 120 K using the EPR technique. Radiation damage center was attributed to ĊHCH2CH2 radical. The principal values of the hyper ne coupling tensor of the unpaired electron with the protons and the principal values of the g tensor were determined. The results were found to be in good agreement with the existing literature.

Radiation Damage Centers in Cholesteryl Heptanoate

Cholesterol takes part signi cantly in many biological mechanisms and as important component for manufacture of bile acids, steroid hormones, and several fat-soluble vitamins. To determine magnetic properties of cholesteryl heptanoate (C34H58O2) which is an important cholesteryl ester in human life and new technology, the single crystals of cholesteryl heptanoate were grown by slow evaporation of concentrated ethyl acetate solution and the grown single crystals were irradiated at room temperature with Co γ ray. The radical produced by gamma irradiation has been investigated in the range of temperatures 123 330 K for di erent orientations of the crystal in a magnetic eld by EPR. Radiation damage center was attributed to radical ĊHαCH2β . The g factor and hyper ne coupling constants have slight dependence on temperature and evident dependence on the orientation of the magnetic eld. Determined g factor and hyper ne coupling constants for the radical ĊHαCH2β were found to be anisotropic with the average values gav = 2.0036, (aCHα)av = 14.52 G, (aCH2β )av = 25.78 G.

Electron paramagnetic resonance of gamma-irradiated single crystals of ethan-1,2 disulfonic acid disodium

ESR spectra of ethan-1,2 disulfonic acid disodium (C2H4Na2O6S2) irradiated by 60Co-γ were recorded between 125K and 300K and for different orientations of the crystal in the magnetic field. The spectra were found to be temperature independent. In C2H4Na2O6S2 single crystal, the radiation damage centers caused by a 60Co-γ source were determined as SO2 radical. For SO2 radical, a value of spectroscopic splitting factor g was calculated.

An EPR study on single crystals of dimethyl-1,3-cyclohexanedione by γ-rays

Single crystals of dimethyl-1,3-cyclohexanedione (C8H12O2) were produced by slow evaporation of the concentrated ethyl acetate solutions. These single crystals were exposed to 60Co γ -rays with a dose speed of 0.950 kGy/h at room temperature for 24, 48, and 72 h. The free radicals of the samples irradiated for 48 and 72 h were detected using electron paramagnetic resonance (EPR)–X-band spectrometer. EPR measurements were performed between 120 and 300 K. The sample irradiated for 48 h by γ -rays was rotated in steps of 10° at 298 K. The spectrum parameters were found to be dependent on the temperature. Two radicals were determined in the molecular structure irradiated. These radiation damage centers were called R1 and R2. The average values of g and the hyperfine coupling constants were calculated as follows: a Ha=6.84 G, a Hb=3.60 G, g=2.0040 for R1, a H=28 G, g=2.0062 for R2.