Electron paramagnetic resonance EPR experiments

Recently, approximate MO theories have been applied to a wide range of solid-state phenomena in addition to those reviewed in this paper. A short review of some of these problems indicates its versatility. Messmer and Watkins (3) have used EH to predict the position of N impurity levels in diamond using a 35-atom C lattice. Their calculations indicated the presence of a Jahn-Teller effect in accordance with electron paramagnetic resonance (EPR) experiments. The calculation was successful in explaining the deepening of the N donor level as due to Jahn-Teller distortion. 

Nitroarenes can react with reducing radicals in two general pathways, radical-addition or outer-sphere electron-transfer, although electron transfer can proceed via adducts in an inner-sphere addition/elimination reaction [98]. Prototypical behaviour was established from electron paramagnetic resonance (epr) experiments [99], which showed that hydroxymethyl radicals reduced nitrobenzene via an intermediate adduct, relatively stable in acid but which underwent base-catalyzed heterolysis ... 

To understand the nature of the spins in the polymers, electron paramagnetic resonance (EPR) experiments were carried out using a Bruker ESP 300 spectrometer equipped with a rectangular cavity that has a TE102 mode fi-equency of 9.5 GHz (X band). An ESR-900 continuous flow He cryostat from Oxford Instruments provided temperature control from 4 to 300 K. 

Analyses of polymer microstractures do not allow these possibilities to be unambiguously distinguished. However, electron paramagnetic resonance (EPR) experiments demonstrate that radicals add exclusively to one of the terminal methylenes. When used in conjimction with imsymmetrical dienes with substituents in the 2-position, the term tail addition has been used to refer to addition to the methylene remote from the substituent. Head addition then refers to addition to the methylene bearing the substituent (i.e., head addition =... 

Recently, an artificial DNA, which consists of a DNA-like base sugar, and phosphoric acids, has taken much attention [38]. The artificial DNA has a selectivity of metal ions, which are captured by DNA-like bases, so that the metal ions could be arrayed hierarchically. In fact, many artificial DNAs with various metal ions have been synthesized and reported [39-41], In 2004, Tanaka succeeded in arraying five [H-Cu(II)-H] (H hydroxypyridone) into a DNA duplex [42,43]. Although details of the structure by NMR or X-ray experiments have not yet been available, they revealed that the distance between the copper ions are 3.7 0.1A with electron paramagnetic resonance (EPR) experiments at 1.5 K. Since the available structural information by the experiments is limited, the computational chemistry might contribute to get a deep understanding of the structure of the artificial DNA. 

In electron paramagnetic resonance (EPR) experiments transitions between the Zeeman components of the ground state of the lanthanide ion are studied. These transitions are found in the microwave region of the spectrum. With EPR the crystal-field levels of the ground state can be determined with a much higher accuracy than is possible with optical methods. A clear introduction to EPR and its instrumentation has been given by... 

Electron spin is the basis of the experimental technique called electron paramagnetic resonance (EPR), which is used to study the structures and motions of molecules and ions that have unpaired electrons. This technique is based on detecting the energy needed to flip an electron between its two spin orientations. Like Stern and Gerlach s experiment, it works only with ions or molecules that have an unpaired electron. 

Deep state experiments measure carrier capture or emission rates, processes that are not sensitive to the microscopic structure (such as chemical composition, symmetry, or spin) of the defect. Therefore, the various techniques for analysis of deep states can at best only show a correlation with a particular impurity when used in conjunction with doping experiments. A definitive, unambiguous assignment is impossible without the aid of other experiments, such as high-resolution absorption or luminescence spectroscopy, or electron paramagnetic resonance (EPR). Unfortunately, these techniques are usually inapplicable to most deep levels. However, when absorption or luminescence lines are detectable and sharp, the symmetry of a defect can be deduced from Zeeman or stress experiments (see, for example, Ozeki et al. 1979b). In certain cases the energy of a transition is sensitive to the isotopic mass of an impurity, and use of isotopically enriched dopants can yield a positive chemical identification of a level. 

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