EPR spectroscopy on irradiated nickel tetracyanide in NaCl host lattice: mechanism for the simultaneous formation of reduced and oxidized species

The kinetics of oxidized and reduced Ni²⁺ complexes produced by X-ray irradiation on single crystals of NaCl doped with [Ni(CN)₄]²⁻ is studied by Electron Paramagnetic Resonance at room temperature. The interdependent generation of these two complexes is attributed to migration of the charge compensating vacancy from the reduced to the oxidized complex in a reversible reaction. At higher X-ray doses, there is a predominant formation of the reduced complex.     

Hyperfine interactions and lattice distortion of the F center in KCl, NaCl and LiCl crystals

Detailed embedded-cluster quantum-chemistry (ROHF, UHF and UMP2) calculations of hyperfine interactions for the F center in KCl, NaCl and LiCl are presented. Our values for the isotropic hyperfine interaction show a good general agreement with experiments. We show that a careful treatment of the lattice environment, local lattice distortion, spin polarization and correlation are important for this good agreement.     

Quadrupolar interaction in iridium cyanide mixed-ligands complexes in alkali halide matrices by ESR spectroscopy

Quadrupolar interactions in [IR(CN)₅]³⁻, [Ir(CN)₅Cl]⁴⁻ and [Ir(CN)₄Cl₂]⁴⁻ paramagnece a complexes in alkali halide host lattices are systematically analysed by ESR spectroscopy. The measured quadrupolar interactions are shown to have no clear correlation to the measured unpaired electron populations.     

The shear modulus of the human vocal fold in a transverse direction

The aim of this study was to measure the shear modulus of the vocal fold in a human hemilarynx, such that the data can be related to direction of applied stress and anatomical context. Dynamic spring rate data were collected using a modified linear skin rheometer using human hemilarynges, and converted to estimated shear modulus via application of a simple shear model. The measurement probe was attached to the epithelial layer of the vocal fold cover using suction. A sinusoidal force of 3g was applied to the epithelium, and the resultant displacement logged at a rate of 1kHz. Force measurement accuracy was 20microg and position measurement accuracy was 4microm. The force was applied in a transverse direction at the midmembranous point between the vocal process and the anterior commissure. The shear modulus of the three female vocal folds ranged from 814 to 1232Pa. The shear modulus of the three male vocal folds ranged from 1021 to 1796Pa. These data demonstrate that it is possible to obtain estimates for the shear modulus of the vocal fold while preserving anatomical context. The modulus values reported here are higher than those reported using parallel plate rheometry. This is to be expected as the tissue is attached to surrounding structures, and is under natural tension.     

Carbon-13 EPR Hyperfine Interaction in the Complex [Rh(CN)6]in a KCl Host Lattice

The hyperfine interaction with¹³C in nonenriched [Rh(CN)₆]⁴⁻, in a KCl host lattice at 7 K, is measured by continuous-wave X- and Q-band electron paramagnetic resonance, allowing, for the first time, a comparative study of spin densities on the carbon of the axial cyanide in this complex and in the similar [Co(CN)₆]⁴⁻complex. From the experimental data corrected for dipolar interactions,A_iso= 79.80 × 10⁻⁴cm⁻¹andA_anis= 0.76 × 10⁻⁴cm⁻¹.     

Selection of Species in Divalent Rhodium Hexacyanide Using Pulsed EPR

The superposition of paramagnetic species in CW EPR spectra usually prevents the measurement of spectral parameters. Separation of superimposed species can be performed in field-swept pulsed EPR by choosing a convenient pulse sequence in such a way that species with different relaxation times can be distinctly affected. Computer subtraction between spectra taken under different conditions may lead to better species identification. ForT₂-based selection, the difference between FID-detected and long τ echo-detected spectra is used. This technique is successfully applied to the [Rh(CN)₆]⁴⁻paramagnetic species created by radiation damage in [Rh(CN)₆]³⁻in a KCl host lattice, where spectra corresponding to different positions of a charge-compensating positive-ion vacancy are superimposed.     

Electron spin relaxation via vibronic level of rhodium(II) hexacyanide complex in KCl crystal

Electron spin-lattice relaxation rates for the low-spin [Rh(CN)(6)](4-) complex in KCl were measured by the inversion recovery and saturation recovery techniques, in the range of 5 to 30 K. Angular variation experiments indicate that electron spin-lattice relaxation times present axial symmetry. The data fit very well to a relaxation process involving localized anharmonic vibration modes, also responsible for the g tensor temperature dependence.     

Electron spin-relaxation via vibronic level of nickel (I) and nickel (III) cyanide complexes in NaCl single crystals

Electron spin-lattice relaxation rates for the low spin [Ni(CN)(4)](1-) and [Ni(CN)(4)](3-) complexes in NaCl host lattice were measured by the inversion recovery technique in the temperature range 7-50K. The data for both paramagnetic species fit very well to a relaxation process involving localized anharmonic vibration modes, also responsible for the g-tensor temperature dependence.     

COMPOSITION OF INDOOR AEROSOLS AT EMPEROR QIN''''S TERRA-COTTA MUSEUM, XI''''AN, CHINA, DURING SUMMER, 2004

Particle samples were collected in August 2004 both inside and outside Emperor Qin's Terra-Cotta Museum in Xi'an, China. Mass and chemical composition of total suspended particles (JSP, particles with aerodynamic diameter less than-30μm), PM2.5(particles with aerodynamic diameter <2.5μm) were determined. The average levels of indoor PM2.5 and TSP were 108.4 and 172.4 μg·m-3, respectively, with PM2.5 constituting 62.9% of the TSP mass. Sulfate ((32.4±6.2)%), organics ((27.7±8.0)%), and geological material ((12.5±3.4)%) dominated indoor PM2.5, followed by ammonium ((8.9±2.8)%), nitrate ((7.0±2.9)%), and elemental carbon (EC, (3.9±1.5)%). Particle size distribution varied with the number of tourists in the museum. The size of sulfate, organics, EC, nitrate, and ammonium was found to vary in the range of 0.43 to 3.3 μm in fraction. Ion balance indicated that the aerosol was acidic, with insufficient ammonium ions to neutralize the sulfuric and nitric acids. High concentrations of acidic aerosols will erode the Terra-cotta warriors and horses especially in the summer season with high temperature (30℃) and relative humidity (70%) and undesirable solar radiation inside the museum. More attention should be paid to protecting these precious antiques made 2000 years ago.