Efforts towards a dynamically polarised HD-target

Origin of electron paramagnetic resonance signal in anthracite

Magnetic properties and vanadium oxidation state in α-Li3V2(PO4)3/C composite: Magnetization and ESR measurements

High-frequency electron spin resonance (ESR) measurements of S = 1/2 one-dimensional Heisenberg antiferromagnetic zig-zag chain substance (VO)(SO4)(2,2-bpy) were performed in the temperature region from 1.8 to 265 K. ESR measurements at 265 K show typical powder pattern spectra of the V4+ ion and g || = 1.925 ± 0.001 and g ⊥ = 1.976 ± 0.001 were obtained. Although the magnetic susceptibility shows a maximum at 3.1 K suggesting the existence of a short-range order, no g-shift and line width broadening were observed down to 1.8 K. We suggest that these temperature-independent features of ESR can be attributed to the result of frustration in (VO)(SO4)(2,2-bpy).

Electrical, magnetic, and EPR studies of the quaternary chalcogenides Cu 2AIIBIVX4 prepared by iodine transport

Vanadium‐doped La3Ga5.5Ta0.5O14 single crystal (0.05 mol% in the melt with respect to Ga) grown by the Czochralski method has been investigated using electron paramagnetic resonance (EPR) and optical absorption measurements. The optical energy gap of pure La3Ga5.5Ta0.5O14 single crystal is equal to 4.94 eV, while the value for vanadium‐doped La3Ga5.5Ta0.5O14 single crystal is 3.44 eV. Optical absorption measurements have revealed 444 nm, 700 nm and 1100 nm bands arising mainly from V3+ ions at octahedral sites. Moreover, V4+ ions were found at octahedral sites (525 nm band) for the “as‐grown” crystals and at tetrahedral positions (380 nm CT band and 600‐ and 800 nm dd transitions) for crystals irradiated with γ‐quanta with a dose of 1.2 × 105 Gy. The X‐band EPR measurements have been done at room temperature while rotating the single‐crystal sample around a, b * and c crystal axes. For each rotation direction the observed spectra consist of an intense multiline signal centred at ∼340 mT and a second, weak one at ∼150 mT. The dominant signal can be ascribed to the V4+ ions (S = 1/2, I = 7/2) occupying the Ga1, Ta octahedral positions, with an axial D 3 point symmetry. The principal tensor values are determined as g ∥ = 1.925(5), g ⊥ = 1.958(5), A ∥ = 17.0(5) mT and A ⊥ = 5.8(5) mT. Each principal axis of the vanadium paramagnetic centres indeed reveals three different orientations in La3Ga5.5Ta0.5O14 crystal with respect to the space orientation of the Ga3 tetrahedra connected with the Ga1 octahedron. The low‐field resonance signal could neither be ascribed to iron impurities nor to the V4+ ions (S = 1/2, I = 7/2) occupying other (tetrahedral) positions simultaneously creating the vacancy state. This signal was too weak to perform detailed analysis. There are also presented low‐temperature EPR spectra that did not reveal any new lines. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper describes the design considerations for a dual mode X-band continuous wave (CW) Electron Paramagnetic Resonance (EPR) cavity, for simultaneous EPR measurement and microwave heating of the same sample. An elliptical cavity geometry is chosen to split the degeneracy of the TM110 mode, allowing for a well resolved EPR signal with the TM110,a and TM110,b modes resonating at around 10 GHz and 9.5 GHz, respectively, the latter of which is used for EPR measurements. This geometry has the benefit that the TM010 mode used for microwave heating resonates at 6.1 GHz, below the cut off frequency of the X-band waveguide used for the EPR channel, providing effective isolation between the heating and EPR channels. The use of a pair of 9 µm thick copper clad laminates as the flat cavity walls allows for sufficient penetration of the modulation field (Bmod) into the cavity, as well as maintaining a high cavity Q factor (> 5700) for sensitive EPR measurements. Locating the heating port at an angle of 135° to the EPR port provides additional space for easier coupling adjustment and for larger sample access to be accommodated. The associated decrease of EPR signal strength is fully compensated for by using a 7.2 GHz low pass filter on the heating port. EPR spectra using 1.6 mm and 4.0 mm sample tubes are shown at room temperature (298 K) and 318 K for a standard Cu(acac)2 solution, demonstrating the effectiveness of this dual-mode EPR cavity for microwave heating during EPR detection.

π-Pimer, π-Dimer, π-Trimer, and 1D π-Stacks in a Series of Benzene Triimide Radical Anions: Substituent-Modulated π Interactions and Physical Properties in Crystalline State

Theory of excitation modes in diamond chain compound [formula omitted

Dynamic electron spin resonance (ESR) measurements compare the paramagnetic and antiferromagnetic (AF) properties of superconducting oxides in the range 4 K to room temperature, at 8 MHz and 9.36 GHz. Two are derivatives of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$: I: Nd(${\mathrm{Nd}}_{0.05}$${\mathrm{Ba}}_{0.95}$${)}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$, ${\mathit{T}}_{\mathit{c}0}$=72 K and II: ${\mathrm{Y}}_{0.2}$${\mathrm{Ca}}_{0.8}$${\mathrm{Sr}}_{2}$[${\mathrm{Cu}}_{2}$(${\mathrm{Tl}}_{0.5}$${\mathrm{Pb}}_{0.5}$)]${\mathrm{O}}_{7}$, ${\mathit{T}}_{\mathit{c}0}$=108 K and two are cases where AF ordering dominates the weak superconductivity: III: ${\mathrm{NbO}}_{1.1}$, 1.25\ensuremath{\le}${\mathit{T}}_{\mathit{c}0}$\ensuremath{\le}10 K and IV: ${\mathrm{La}}_{2}$${\mathrm{NiO}}_{4.00}$, 70 K \ensuremath{\ge}${\mathit{T}}_{\mathit{c}0}$\ensuremath{\ge}40 K. At temperatures 298\ensuremath{\ge}T\ensuremath{\ge}64 K, the ESR absorption by I indicates orthorhombic symmetry. The peaks at ${\mathit{g}}_{\mathit{c}}$=2.06, ${\mathit{g}}_{\mathit{b}}$=2.13, and ${\mathit{g}}_{\mathit{a}}$=2.24 are identified with the presence of 5% ${\mathrm{Nd}}^{3+}$${(}^{4}$${\mathit{I}}_{9/2}$) in the Ba layer because the characteristic ${\mathrm{Cu}}^{2+}$ impurity hyperfine structure is absent and the ESR signal disappears several degrees below ${\mathit{T}}_{\mathit{c}}$. Near ${\mathit{T}}_{\mathit{c}}$ the ESR absorption is reduced by two orders of magnitude.Proximity effects give rise to interference fringes with period ${\mathrm{\ensuremath{\tau}}}_{\mathit{f}}$(T) independent of the field B and the rate of sweep ${\mathit{dB}}_{\mathit{z}}$/dt. ESR is observed below ${\mathit{T}}_{\mathit{c}}$ because flux penetrates the superconductor. The temperature dependence of ${\mathrm{\ensuremath{\tau}}}_{\mathit{f}}$ leads to an activation energy for the flux motion ${\mathit{E}}_{\mathit{a}}$(I)/R\ensuremath{\le}16 K and ${\mathit{E}}_{\mathit{a}}$ (III)/R\ensuremath{\simeq}3 K \ensuremath{\simeq}${\mathit{T}}_{\mathit{c}}$/4. In the superconducting state a coherent flux expulsion response to a change in ${\mathit{B}}_{\mathit{z}}$ from 500 mT to zero is observed in times ${\mathrm{\ensuremath{\tau}}}_{\mathit{r}}$=8 to 10 s. The inverse rate of noise spikes due to flux expulsion, when the samples are cooled through ${\mathit{T}}_{\mathit{c}}$ in a magnetic field, varies from ${\mathrm{\ensuremath{\tau}}}_{\mathrm{noise}}$=3.5 s for III to 21 s for IV. The microwave absorption spectra identify three temperature regimes: (i) For 3.5 K T${\mathit{T}}_{\mathit{m}}$\ensuremath{\simeq}${\mathit{T}}^{\mathrm{*}}$${\mathit{T}}_{\mathit{c}}$, superconducting behavior was confirmed by the energy loss near zero magnetic field and the kinetics of high-field noise due to flux expulsion. Near g=2.00 ESR absorption is observed for all materials. A broad absorption near 50 to 100 mT at 9.36 GHz has been attributed to AF resonance. (ii) ${\mathit{T}}_{\mathit{m}}$\ensuremath{\simeq}${\mathit{T}}^{\mathrm{*}}$\ensuremath{\le}T\ensuremath{\le}${\mathit{T}}_{\mathit{c}}$ identifies the range where flux motion gives rise to interference fringes in the ESR absorption. (iii) ESR and AF resonance are observed immediately after warming above ${\mathit{T}}_{\mathit{c}}$.

Reconstruction of doses absorbed by radiotherapy patients by means of EPR dosimetry in tooth enamel

ROS: a step closer to elucidating their role in the etiology of light-induced skin disorders.

Room-temperature ferromagnetism and hydrogen shallow donors in rare-earth Eu-doped ZnO nanorods

ABSRTACTIn this article, we report low-temperature electron spin resonance (ESR) investigations carried out on solution processed three-layer inverted solar cell structures: PC61BM/CH3NH3PbI3/PEDOT:PSS/Glass, where PC61BM and PEDOT:PSS act as electron and hole transport layers, respectively. ESR measurements were conducted on ex-situ light (1 Sun) illuminated samples. We find two distinct ESR spectra. First ESR spectra resembles a typical powder pattern, associated with gx = gy = 4.2; gz = 9.2, found to be originated from Fe3+ extrinsic impurity located in the glass substrate. Second ESR spectra contains a broad (peak-to-peak line width ∼ 10 G) and intense ESR signal appearing at g = 2.008; and a weak, partly overlapped, but much narrower (peak-to-peak line width ∼ 4 G) ESR signal at g = 2.0022. Both sets of ESR spectra degrade in intensity upon light illumination. The latter two signals were found to stem from light-induced silicon dangling bonds and oxygen vacancies, respectively. Our controlled measurements confirm that these centers were generated during UV-ozone treatment of the glass substrate –a necessary step to be performed before PEDOT:PSS is spin coated. This work forms a significant step in understanding the light-induced- as well as extrinsic defects in perovskite solar cell materials.

Innovating dosimetric materials, which includes design and development of new dosimetric materials based on rare earth oxides, is challenging. Yttrium oxide (Y[Formula: see text]O[Formula: see text] is one of the most important sesquioxides and presents crystal characteristics that enable doping with rare earth ions, making it a promising material for radiation dosimetry. This paper reports on the development and measurement of Electron Paramagnetic Resonance (EPR) signal response for Y[Formula: see text]Eu[Formula: see text]O[Formula: see text][Formula: see text]micro rods that have undergone facile low-pressure hydrothermal synthesis and bio-prototyping. As- synthesized powders with narrow sub-micrometer particle size distribution with d[Formula: see text][Formula: see text] of 584 nm exhibited a reactive surface, which led to the formation of stable aqueous suspensions by controlling the surface charge density of particles through alkaline pH adjustment. Ceramic samples with dense microstructure were formed by sintering at 1600 [Formula: see text]C for 4h at ambient atmosphere. Y[Formula: see text]Eu[Formula: see text]O[Formula: see text][Formula: see text]micro rods were irradiated using a [Formula: see text]Co source with doses from 1 to 100 kGy, and EPR spectra were measured at room temperature in X-band microwave frequencies. Sintered samples exhibited linearity of the main EPR signal response from 10 Gy to 10 kGy. Supralinearity was observed for higher doses, which is possibly ascribed to formation of more defects. Using europium as a dopant enhanced the EPR signal of yttrium rods remarkably, due to 4f–4f transitions of the Eu[Formula: see text] ion. These innovative findings make europium-doped yttrium oxide a promising material for radiation dosimetry.

EPR study of radiation damage to DNA irradiated with synchrotron soft X-rays around nitrogen and oxygen K-edge