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Since the first.EPR/ESR spectrum of a paramagnetic substance was published over 70 years ago, the technical improvements did not occur until after/during World War II with the advent of radar technology. The approaches to biomedic...
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Since the first.EPR/ESR spectrum of a paramagnetic substance was published over 70 years ago, the technical improvements did not occur until after/during World War II with the advent of radar technology. The approaches to biomedical problems started somewhat later with the real burst of activity starting after the birth of the spin label technique about 50 years ago. The applications to proteins, then membranes and nucleic acids, and later applications to cells and eventually in-vivo on small animals and now humans has led EPR/ESR to finally being recognized as a uniquely powerful technique in the toolbox of techniques probing macromqlecules and their interactions, free radical biology and its eventual value as a diagnostic technique. This article gives an overview of EPR/ESR studies of biomedically related systems, including proteins and enzymes. It presents a very personal historical perspective, briefly reviews the origins of the technique and reflects on possible future directions. As with NMR, advances in molecular biology and technology drastically changed the nature and focus of the technique, particularly the site directed spin labeling method that has been invaluable in determining protein and macromolecular structure by both EPR and NMR.
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The ages of fault events of active faults have been estimated using electron spin resonance (ESR) signals of siliceous gouges. This technique of ESR method is limited by obtaining only ages that are greater than tens of millennia....
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The ages of fault events of active faults have been estimated using electron spin resonance (ESR) signals of siliceous gouges. This technique of ESR method is limited by obtaining only ages that are greater than tens of millennia. So this study focuses on developing a new technique of using calcareous gouges to gain an insight into the ages of latest seismogenic event within the Holocene. For the first time, signal B of the ESR method has been used to estimate the age of the Ushikubi fault from calcareous gouge. This technique proved reliable because the mean age (1.9 ka) obtained agrees with previous works on indirect age determination of latest fault events by utilizing radiocarbon dating in the study area. However, the result from the ESR technique showed an increase relative to the age of 1 ka that was obtained by the radiocarbon dating method. This disparity may be due to a high dose rate value of 50 Gy/h of artificial irradiation that was used to determine the equivalent dose (ED). Moreover, isochronal experiment revealed that the gouge did not comprise pure carbonates but consisted of a mixture of calcite and quartz grains. A younger age value would have been obtained if a lower artificial irradiation dose rate and a relatively pure carbonate fault gouge were used in the ED determination.
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We report millimetre-wave electron spin resonance (ESR) measurements on single crystals of the high-spin molecules Cr_(10)(OMe)_(20)(O_2CCMe_3)_(10) and Cr_(12)O_9(OH)_3(O_2,CCMe_3)_(15) within a temperature range of 1.4 K to 50 K...
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We report millimetre-wave electron spin resonance (ESR) measurements on single crystals of the high-spin molecules Cr_(10)(OMe)_(20)(O_2CCMe_3)_(10) and Cr_(12)O_9(OH)_3(O_2,CCMe_3)_(15) within a temperature range of 1.4 K to 50 K and in magnetic fields of up to 5 Tesla. In our experiments it is possible to vary the orientation of the magnetic field with respect to the crystal axes, and thus to study the ESR lireshapes as a function of both temperature and angle. Our results confirm that Cr_(10)(OMe)_(20)(O_2CCMe_3)_(10) behaves as a single-molecule magnet with 5 = 15 and D = - 0.03 K, while Cr_(12)O_9(OH)_3(O_2,CCMe_3)_(15) has S = 6 and D ~ 0.1 1C. A comparison of the experimental spectra with numerical simulations gives good agreement at low temperatures. At higher temperatures, we observe a nairowing of the ESR spectrum that is not explained by simple models.
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EPR studies of Y0.03Ca0.97F2.03 : Gd3+ and Y0.03Cd0.97F2.03 : Gd3+ single crystals revealed the presence of Gd3+ ions embedded in yttrium clusters. The symmetry of the paramagnetic centers was determined, and the fine-structure pa...
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EPR studies of Y0.03Ca0.97F2.03 : Gd3+ and Y0.03Cd0.97F2.03 : Gd3+ single crystals revealed the presence of Gd3+ ions embedded in yttrium clusters. The symmetry of the paramagnetic centers was determined, and the fine-structure parameters were estimated both experimentally and theoretically. (c) 2005 Pleiades Publishing, Inc.
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Light-induced ESR (LESR) measurements have been applied on the halogen-bridged metal complex (MX-chain), Pd(chxn)_2Br_3, to study the dynamics of the photogenerated spin such as neutral soliton and polaron. The time evolution of t...
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Light-induced ESR (LESR) measurements have been applied on the halogen-bridged metal complex (MX-chain), Pd(chxn)_2Br_3, to study the dynamics of the photogenerated spin such as neutral soliton and polaron. The time evolution of the LESR intensity is interpleted in terms of the pair-creaton and recombination model of photogenerated spins which are separated by the finite potential barriers on the chain. The LESR intensity showed the same excitation power dependence with the one in the Pt-Cl compound.
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Electronic and molecular structures of high-spin polycarbenes with dendrimeric structure, which are topologically extended using ethynyl and phenyl groups, have been studied by cw- and pulsed ESR spectroscopy. Two-dimensional elec...
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Electronic and molecular structures of high-spin polycarbenes with dendrimeric structure, which are topologically extended using ethynyl and phenyl groups, have been studied by cw- and pulsed ESR spectroscopy. Two-dimensional electron spin transient nutation method based on pulsed ESR spectroscopy was applied to the polycarbenes in order to identify their molecular spin multiplicity. We determined the fine-structure parameters of the triscarbene and the molecular structure based on a semiempirical treatment of a fine-structure tensor. It is shown that the stable brominated diphenylcarbenes with the triplet ground state serve as useful building blocks for the super high-spin molecules and the superparamagnetic materials.
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The g-tensor and relaxation mechanism of ground-state high-spin (Fe(III)OEP)Cl (OEP:octaethylporphyrin) magnetically diluted in diamagnetic Ni(II)OEP single crystals were determined by cw- and pulsed-ESR spectroscopy. From cw-ESR ...
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The g-tensor and relaxation mechanism of ground-state high-spin (Fe(III)OEP)Cl (OEP:octaethylporphyrin) magnetically diluted in diamagnetic Ni(II)OEP single crystals were determined by cw- and pulsed-ESR spectroscopy. From cw-ESR measurements the degree of the rhombicity in fine-structure interaction was determined. It was suggested that the rhombicity is attributable to the pseudo Jahn4eller effect and that the line broadening with increasing temperature is due to the dynamic Jahn-Teller phenomenon among the distorted structures. The large fine-structure constant D was determined to be +7 cm~(-1) by measuring the dependences of the spin-lattice relaxation rate on the temperature with the magnetic field perpendicular to the porphyrin plane. The spin-lattice relaxation times highly depend on the direction of the static magnetic field. The orientation dependence was interpreted in terms of the spin sublevel mixing by the spin-orbit interaction.
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A mixture of molecular high-spin species is frequently observed in a variety of model systems for molecule-based magnetics. Two-Dimensional Electron Spin Transient Nutation (2D-ESTN) spectroscopy based on pulsed ESR is useful to d...
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A mixture of molecular high-spin species is frequently observed in a variety of model systems for molecule-based magnetics. Two-Dimensional Electron Spin Transient Nutation (2D-ESTN) spectroscopy based on pulsed ESR is useful to discriminate between high-spin species in spin mixtures and identify unequivocally the spin quantum number of them. In this work, we have performed the spectral simulation of the 2D ESTN spectrum including forbidden transitions for Eu~(2+) ion (S=7/2, I=5/2) in a CaF_2 single crystal, which has two isotopes (~(151)Eu (47.9 percent) and ~(153)Eu (52.1 percent)), based on the transition moment analysis including nuclear spin transitions. The simulated spectrum is reasonably consistent with the experimental one, indicating that the transition moment spectroscopy-based simulation is a powerful tool for the unequivocal identification of the 2D-ESTN spectra from a mixture of electronic and nuclear high-spin systems.
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Electronic and molecular structures of mononitrene1 and bisnitrene 2 derived from 2,4,6-triazide-s-triazine 4 byphotolysis have been studied by powder-pattern and single-crystalESR spectroscopy. The experimentally determined fine-...
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Electronic and molecular structures of mononitrene1 and bisnitrene 2 derived from 2,4,6-triazide-s-triazine 4 byphotolysis have been studied by powder-pattern and single-crystalESR spectroscopy. The experimentally determined fine-structureparameters D and E were 1.402 and 0.011 cm~(-1) for 1 (S=1),and 0.280 and 0.058 cm~(-1) for 2 (S=2), respectively. Thesevalues are much larger than those of phenylnitrenes (S=1) and m-phenylenebisnitrenes (S=2). The fine-structure parameters of thebisnitrene 2 were interpreted by a semiempirical model consideringdominant one-center spin-spin interactions at the monovalentnitrogen atoms, indicating that the #pi#-electron spins are morelocalized on the monovalent nitrogen atoms and that the #pi#-delocalization effect is hampered by introducing heteroatoms intothe #pi#-conjugation system.
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Persisten high-spin polycarbene, 1,3,5-tris(p-ethynyldiphenylmethylene) benzene was studied by Electron SpinTransient Nutation (ESTN) spectroscopy in non-oriented media.2D-ESTN spectra of the polycarbene were measured in order toi...
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Persisten high-spin polycarbene, 1,3,5-tris(p-ethynyldiphenylmethylene) benzene was studied by Electron SpinTransient Nutation (ESTN) spectroscopy in non-oriented media.2D-ESTN spectra of the polycarbene were measured in order toidentify a molecular spin multiplicity of the high-spin state. Theobserved nutation frequencies were assigned to those arising fromthe allowed ESR transitions of the septet ground state (S=3). Itindicates that the high-spin state is generated by ferromagneticinteraction between stable bromosubstituted diphenylmethylenes(S=1) through a 2D topological spin coupling unit with C_3symmetry, 1,3,5-tris(ethynyl) benzene. The high-spin polycarbenehas survied after annealing of the galss matrix. The triplet carbeneunit is supposed to serve as a useful building block for extendedsuperhigh-spin molecular systems and organic superparamagnets.
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