Search results for "Electron nuclear double resonance"
showing 10 items of 15 documents
Structural analysis of Cu(II) ligation to the 5'-GMP nucleotide by pulse EPR spectroscopy.
2007
JBIC Journal of Biological Inorganic Chemistry, 12 (6)
Si29Hyperfine Structure of theE′αCenter in Amorphous Silicon Dioxide
2006
We report a study by electron paramagnetic resonance on the $E^{\ensuremath{'}}{}_{\ensuremath{\alpha}}$ point defect in amorphous silicon dioxide ($a\mathrm{\text{\ensuremath{-}}}{\mathrm{SiO}}_{2}$). Our experiments were performed on $\ensuremath{\gamma}$-ray irradiated oxygen-deficient materials and pointed out that the $^{29}\mathrm{Si}$ hyperfine structure of the $E^{\ensuremath{'}}{}_{\ensuremath{\alpha}}$ consists of a pair of lines split by $\ensuremath{\sim}49\text{ }\text{ }\mathrm{mT}$. On the basis of the experimental results, a microscopic model is proposed for the $E^{\ensuremath{'}}{}_{\ensuremath{\alpha}}$ center, consisting of a hole trapped in an oxygen vacancy with the un…
EPR on Radiation-Induced Defects in SiO2
2014
Continuous-wave electron paramagnetic resonance (EPR) spectroscopy has been the technique of choice for the studies of radiation-induced defects in silica (SiO2) for 60 years, and has recently been expanded to include more sophisticated techniques such as high-frequency EPR, pulse electron nuclear double resonance (ENDOR), and pulse electron spin echo envelope modulation (ESEEM) spectroscopy. Structural models of radiation-induced defects obtained from single-crystal EPR analyses of crystalline SiO2 (alfa-quartz) are often applicable to their respective analogues in amorphous silica (a-SiO2), although significant differences are common.
Similarity and Specificity of Chlorophyll b Triplet State in Comparison to Chlorophyll a as Revealed by EPR/ENDOR and DFT Calculations
2019
An investigation of the photoexcited triplet state of chlorophyll (Chl) b has been carried out by means of electron nuclear double resonance, both in a frozen organic solvent and in a protein environment provided by the water-soluble chlorophyll protein of Lepidium virginicum. Density functional theory calculations have allowed the complete assignment of the observed hyperfine couplings corresponding to the methine protons and the methyl groups, leading to a complete picture of the spin density distribution of the triplet state in the tetrapyrrole macrocycle. The triplet-state properties of Chl b are found to be similar, in many respects, to those previously reported for Chl a, although som…
Au25(SEt)18 a nearly naked thiolate-protected Au25 cluster Struct. analysis by single crystal X-ray crystallograp. and electron nuclear double res
2014
X-ray crystallography has been fundamental in discovering fine structural features of ultrasmall gold clusters capped by thiolated ligands. For still unknown structures, however, new tools capable of providing relevant structural information are sought. We prepared a 25-gold atom nanocluster protected by the smallest ligand ever used, ethanethiol. This cluster displays the electrochemistry, mass spectrometry, and UV-vis absorption spectroscopy features of similar Au25 clusters protected by 18 thiolated ligands. The anionic and the neutral form of Au25(SEt)18 were fully characterized by (1)H and (13)C NMR spectroscopy, which confirmed the monolayer's properties and the paramagnetism of neutr…
Cryogenic 35GHz pulse ENDOR probehead accommodating large sample sizes: Performance and applications.
2009
The construction and performance of a cryogenic 35GHz pulse electron nuclear double resonance (ENDOR) probehead for large samples is presented. The resonator is based on a rectangular TE(102) cavity in which the radio frequency (rf) B(2)-field is generated by a two turn saddle ENDOR coil crossing the resonator along the sample axis with minimal distance to the sample tube. An rf power efficiency factor is used to define the B(2)-field strength per square-root of the transmitted rf power over the frequency range 2-180MHz. The distributions of the microwave B(1)- and E(1)-field, and the rf B(2)-field are investigated by electromagnetic field calculations. All dielectrics, the sample tube, and…
Computational modeling of isotropic electron paramagnetic resonance spectra of doublet state main group radicals
2007
The combined use of theoretical and mathematical methods in the analysis of electron paramagnetic resonance data has greatly increased the ability to interpret even the most complex spectra reported for doublet state inorganic main group radicals. This personal account summarizes the theoretical basis of such an approach and provides an in-depth discussion of some recent illustrative examples of the utilization of this methodology in practical applications. The emphasis is on displaying the enormous potential embodied within the approach. peerReviewed
Electron paramagnetic resonance in a biomedical laboratory
2013
Investigation on the microscopic structure of E' center in amorphous silicon dioxide by electron paramagnetic resonance spectroscopy
2006
The E′δ center is one of the most important paramagnetic point defects in amorphous silicon dioxide ( a-SiO 2) primarily for applications in the field of electronics. In fact, its appearance in the gate oxide of metal-oxide-semiconductor (MOS) structures seriously affects the proper work of many devices and, often, causes their definitive failure. In spite of its relevance, until now a definitive microscopic model of this point defect has not been established. In the present work we review our experimental investigation by electron paramagnetic resonance (EPR) on the E′δ center induced in γ-ray irradiated a-SiO 2. This study has driven us to the determination of the intensity ratio between…
A magnetic look into the protecting layer of Au25 clusters
2016
The field of molecular metal clusters protected by organothiolates is experiencing a very rapid growth. So far, however, a clear understanding of the fine interactions between the cluster core and the capping monolayer has remained elusive, despite the importance of the latter in interfacing the former to the surrounding medium. Here, we describe a very sensitive methodology that enables comprehensive assessment of these interactions. Pulse electron nuclear double resonance (ENDOR) was employed to study the interaction of the unpaired electron with the protons of the alkanethiolate ligands in four structurally related paramagnetic Au25(SR)0 18 clusters (R ¼ ethyl, propyl, butyl, 2-methylpro…