共查询到20条相似文献,搜索用时 93 毫秒
1.
W. D. Hutchison A. V. J. Edge N. Yazidjoglou D. H. Chaplin 《Hyperfine Interactions》1992,75(1-4):291-298
The high resolution hyperfine spectroscopy, modulated adiabatic passage of oriented nuclei (MAPON), has been applied for the
first time to high purity, elemental systems. Detailed comparisons between the electric quadrupole hyperfine interactions
(EQI’s) and, in particular, their distributions, are obtained for60CoCo where the hosts are a single crystal of hcp cobalt and a polycrystalline cobalt foil of predominantly fcc character. For
hcp Co, with the electronic magnetization, M, parallel to the c-axis, the mode value P/h=3e2qQ/4I(2I−1)h=−48.5(5) kHz. This fractional distribution implies the sharpest electric field gradient (efg) measured in a metal
to date, using MAPON spectroscopy, in excess of two times sharper than that of the most dilute impurity efg in a crystallographically
cubic ferromagnetic host. The mode efg is Vzz=−27.3(32)×1019 Vm−2. For the polycrystalline, predominantly fcc foil, prepared by quenching, the EQI mode value is P/h=−6.2(4) kHz with a FWHM
of 12.0(7) kHz yielding a mode efg of Vzz=−3.5(5)×1019 Vm−2. 相似文献
2.
B S Prabhananda 《Pramana》1990,34(6):491-506
The “minimum linewidths” seen in the ESR linewidths against temperature plots, the dependence of line widths on the63Cu nuclear magnetic quantum numbers and the Hubbard relation provide sufficient number of equations to determine the anisotropic
ESR parameters in the case of axially symmetric Cu(II) complexes even when unresolved hyperfine structures make contributions
to linewidths. After testing the method by reanalysing the literature data on Cu(II) bis-acetylacetonate, it has been used
to obtain the anisotropic ESR parameters in the case of bis-salicylaldehydate of Cu(II). Linewidth contributions from unresolved
hyperfine structures associated with the1H of coordinating CHCl3 inferred in these studies, were confirmed by comparing the widths in CHCl3 and CDCl3 under ideal conditions. The temperature dependence of this contribution and the estimate of rate constant at room temperature
(∼ 1010 s−1) suggest that the coordinating solvent exchange is diffusion controlled. 相似文献
3.
Electron spin resonance (ESR) study was done on calcite encrustation on Fili neotectonic fault surface, Greece. Normally such
calcite encrustations on fault surfaces are not observed. Significantly, the ESR study has detected the presence of nitrate
NO32− radical in this calcite encrustation, havingg
⊥=2.0063±0.0001 and hyperfine coupling constantA
⊥=3.44 mT, the second such detection of nitrate NO32− radical following a sample from Scott Glacier, Antarctica. From isochronal thermal annealing measurement the NO32− radical was found to be quite stable, only fully annealed at 475°C. This study also shows that the ESR, as a tool, can be
suitably applied to date the age of formation of the calcite encrustation with SO3− as an ESR dating signal by additive γ-ray irradiation. A preliminary estimation indicates the age of formation of calcite
precipitation at Fili fault, Greece to be about 5600 years. 相似文献
4.
Konstantin Tarasov Patricia Beaunier Michel Che Eric Marceau Yanling Li 《Journal of nanoparticle research》2011,13(5):1873-1887
Following procedures formerly developed for the preparation of supported heterogeneous catalysts, carbon-coated cobalt nanoparticles
dispersed on porous alumina have been prepared by impregnation of γ-Al2O3 with (NH4)2[Co(EDTA)] and thermal decomposition in inert atmosphere. Below 350 °C, Co(II) ions are complexed in a hexa-coordinated way
by the EDTA ligand. The thermal treatment at 400–900 °C leads to the EDTA ligand decomposition and recovering of the support
porosity, initially clogged by the impregnated salt. According to X-ray absorption spectroscopy, and due to in situ redox
reactions between the organic ligand and Co(II), both oxidic and metallic cobalt phases are formed. Characterisation by transmission
electron microscopy, X-ray diffraction and magnetic measurements reveals that an increase in the treatment temperature leads
to an increase of the degree of cobalt reduction as well as to a growth of the cobalt metal particles. As a consequence, the
samples prepared at 400–700 °C exhibit superparamagnetism and a saturation magnetisation of 1.7–6.5 emu g−1 at room temperature, whilst the sample prepared at 900 °C has a weak coercivity (0.1 kOe) and a saturation magnetisation
of 12 emu g−1. Metal particles are homogeneously dispersed on the support and appear to be protected by carbon; its elimination by a heating
in H2 at 400 °C is demonstrated to cause sintering of the metal particles. The route investigated here can be of interest for obtaining
porous magnetic adsorbents or carriers with high magnetic moments and low coercivities, in which the magnetic nanoparticles
are protected from chemical aggression and sintering by their coating. 相似文献
5.
We report the nuclear orientation of near-stoichiometric samples of ZrZn2 containing trace impurities of radioactive54Mn and60Co in the temperature range 6.5–60 mK and in applied fields between 0.2 and 5.7 T. Analysis of the resullts indicates that
in both cases, the transition-element impurities occupy two sites (the Zr and Zn sites) with about equal probablities. In
one site, most probably that of Zr, both impurities have positive hyperfine fields of +12.0 T and +3.8 T for Mn and Co, respectively;
in the other site, the corresponding hyperfine fields are negative, with the values −6.0 T and −6.9 T. The dynamic hyperfine
interaction of Mn in ZrZn2 has also been studied using the thermal cyclic method with a weak thermal link, and was analyzed for the two relaxation times
corresponding to the different lattice sites. 相似文献
6.
The temperature dependences of the rates of the degenerate electron transfer of various viologens (1,1′-di(hydrocarbyl)-4,4′-bipyridinium
salts) are measured in seven different solvents by means of electron spin resonance (ESR) line broadening. Rates vary between
1.7·108 and 1.1·109 M−1s−1 at room temperature and clearly show a solvent dynamical effect, which is inferred from the dependence of the rate constants
on the longitudinal relaxation time of the solvent. Activation energies ranging from 5.3 to 24.4 kJ mol−1 are found. For the first time, hyperfine coupling constants are reported for the radical cations of the hydroxyethyl viologen
and the amino viologen based on both continuous-wave ESR and electron-nuclear double resonance spectroscopy. Furthermore,
the temperature and the solvent dependence of the hyperfine coupling constants of the methyl viologen radical cation are reported. 相似文献
7.
S. Yu. Paranchich L. D. Paranchich M. D. Andriichuk V. R. Romanyuk V. N. Makogonenko Yu. V. Tanasyuk T. A. Mel’nichuk 《Journal of Applied Spectroscopy》2007,74(1):81-85
We present the results of experimental studies of the optical properties of cobalt-doped Cd
x
H1−x
Se (x = 0.18) single crystals with cobalt ion concentrations of NCo = 5·1018, 5·1019, and 1·1020 cm−3 at T = 90 K and 300 K. The composition (x = 0.18) of the Cd
x
Hg1−x
Se solid solution was selected so that the hypothetical resonance level is found on the bottom of the conduction band. We
show that the cobalt ions in the mercury selenide can form a resonance donor level only for cobalt concentrations NCo < 5·1018 cm−3. For NCo ∼ 5·1018 cm−3, the cobalt ions substitute for mercury atoms, forming a solid solution and leading to an increase in the bandgap width and
a change in the physical properties. The solubility of cobalt in the HgSe lattice can be greater than 5%–10%.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 73–77, January–February, 2007. 相似文献
8.
We obtained57Fe hyperfine field parameters from Fe1−x-Co
x
alloys (0≤x≤0.6) from 77 K to 900 K. We first discuss the origin of the low temperature hyperfine fields in terms of the 3d and 4s electrons
at57Fe atoms. The57Fe hyperfine magnetic field (hmf) of Fe-Co alloys depends more weakly on temperature than the hmf of pure Fe. This temperature
dependence occurs because the alignment of the magnetic moments at both the Fe atoms and at the Co atoms depend on temperature
in the same way as the bulk magnetization of Fe-Co alloys. 相似文献
9.
In order to study the effects of large-surface-area solids on the formation of biomacromolecules, copper(II)-nucleosides complexes
were studied in water at high pH and after contact with the cavity walls of 13X-zeolite. The results were mainly collected
by electron spin resonance in continuous (cw-ESR) and pulsed (ESE) wave. Particular attention was dedicated to adenosine as
a nucleoside model for the formation of compounds which were fully characterized in alkaline water solution and after adsorption
on commercial 13X-zeolite. In aqueous solution, adenosine was coordinated to copper(II) through deprotonated hydroxyl groups
in the 2′ and 3′ positions of the ribose unit, with the formation of [Cu(adenosine)2(H2O)2]2−. When adsorbed on zeolite, both cw-ESR and ESE showed that a fraction of the adsorbed complexes did not change their structure
and showed high mobility in the zeolite faujasite cavity. The remaining fraction directly interacted with27Al nuclei of the zeolite framework. Other copper(II)-nucleosides behaved in the same manner. Surprisingly enough, alkaline
solutions of nucleosides were able to remove copper (II) from zeolite in the form of [Cu(adenosine)2(H2O)2]2− which freely moved in the supernatant aqueous liquid. 相似文献
10.
H. Keller R. F. Kiefl Hp. Baumeler W. Kündig B. D. Patterson J. Imazato K. Nishiyama K. Nagamine T. Yamazaki R. I. Grynszpan 《Hyperfine Interactions》1986,31(1-4):461-466
The hyperfine field (B
μ
hf
) at the negative muon μ− in ferromagnetic iron was investigated by means of the zero-field μ− spin precession technique. In the temperature range 320–690 K,B
μ
hf
for μ− Fe departs from the magnetization curve of pure iron in the same way as the hyperfine field seen by a55Mn impurity in dilute MnFe measured by NMR. The hyperfine anomaly for μ− Fe relative to dilute (1.5 at.%)55Mn in iron is found to be −0.9(3)% and temperature independent over the temperature range investigated. 相似文献
11.
Electron paramagnetic resonance studies have been carried out at 300 K on the Cu(II)-doped [Zn(C3H2O4)2(H2O)2] system in single-crystal and powder forms in order to rationalize the low parallel 63Cu hyperfine value. Angular variation of the hyperfine resonances in the three orthogonal planes shows the presence of only
one magnetic site with g and A values equal to g
zz
= 2.455, g
yy
= 2.121, g
xx
= 2.105 and A
zz
= 160.9 · 10−4 cm−1, A
yy
= 12.5 · 10−4 cm−1, A
xx
= 7.35 · 10−4 cm−1. The crystal structure of the host lattice is isostructural with the corresponding cobalt complex and contains two molecules
per unit cell. The low magnitude of A
zz
value for the complex is rationalized in terms of an admixture of the
ground state with the
excited state and delocalization of the unpaired spin density onto the ligands. In addition, the highest hyperfine value
obtained from the single-crystal data (160.9 · 10−4 cm−1) is considerably larger than that obtained from the powder spectrum (138 · 10−4 cm−1).
Authors' address: P. Sambasiva Rao, Department of Chemistry, Pondicherry University, Pondicherry 605014, India 相似文献
12.
N. P. Baran V. M. Maksimenko V. V. Teslenko A. A. Bugay 《Journal of Applied Spectroscopy》2008,75(1):15-20
EPR spectra of barium dithionate hydrate single crystals γ-irradiated at low (80 Gy) and high (10 kGy) doses are studied.
Four lines, the strongest of which is due to the SO3− radical, are observed in the EPR spectrum of the low-irradiated samples. Another line seems to belong to SO2−. The strong line and weak lines with hyperfine structure and lines for pairs of closely spaced SO3− centers with a strong angular dependence are observed at high irradiation doses. The main values of the SO3− hyperfine coupling tensor and the dipole-dipole coupling constants of the SO3− pairs are determined. A quantum-chemical calculation of the electronic structure of isolated SO3− and SO2− radicals is performed. Values of the g tensors and hyperfine couplings are calculated.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 1, pp. 18–22, January–February, 2008. 相似文献
13.
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. 相似文献
14.
L. Tian J. L. Zhu L. Chen B. An Q. Q. Liu K. L. Huang 《Journal of nanoparticle research》2011,13(8):3483-3488
α-Cobalt hydroxide was synthesized by a facile hydrothermal process from Co(Ac)2 and NH3·H2O in the presence of 1,3-propanediol. The large-scale-prepared cobalt hydroxide has a uniform nanobelt morphology with a considerably
high aspect-ratio more than 20 which may be advantageous for exploration of their physicochemical properties. This synthetic
method is convenient, economical, and controllable. The samples were characterized by powder X-ray diffraction, energy dispersive
spectrum, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, CHN element
analysis, thermogravimetric and differential-thermogravimetric analysis, which revealed the compound is lamellar structural
cobalt organic–inorganic hybrid with the chemical formula of Co(OH)1.49(NH3)0.01(CO3
2−)0.22(Ac−)0.07(H2O)0.11 and single-crystalline. 相似文献
15.
Electron paramagnetic resonance studies were conducted on the photoinduced charge transfer and also hyperfine interaction
of U5+ stabilized in photorefractive matrix LiNbO3. This work deals with: (i) first observation of hyperfine structure due to233U (I=5/2) in its pentavalent state at octahedral sites and comparison with other possible site symmetries, (ii) photoinduced charge
transfer as observable by EPR and its relevance to photorefractive behaviour of LiNbO3. The effect of chemical bonding on the hyperfine interaction of 5f
1 configuration was also studied by converting the existing literature data on235U5+ to that of233U5+ by standard methods. This suggests that progressive substitution of oxygen by F−, in the series UO
6
7−
, (UO5F)6− and (UO4F2)5− drastically decreases the hyperfine coupling constantA
∥, along the local distortion axis. This trend is explained as being due to the absence of ligand ion along the distortion
axis at U5+ site in trigonal LiNbO3. The effects of illumination by copper vapor laser (CVL) on the intensity of the U5+ signal was studied in the 10–300K region. The kinetics of decay and restoration of U5+ was also studied between 10–100K range. The decay kinetics was found to obey double exponential. The reduction of concentration
of U5+ with CVL-illumination and its restoration in the absence of light show that pentavalent uranium takes part in the photorefractive
effects in LiNbO3. 相似文献
16.
I. N. Antsigin S. V. Gorbunov A. V. Kruzhalov B. V. Shulgin 《Hyperfine Interactions》1990,60(1-4):881-884
The hyperfine structure of ESR spectra of new paramagnetic centres in neutron exposed and X-rayed beryllium single crystals
was identified. A new data on hyperfine interaction in Zn+ and P− centres are presented. Spin-Hamiltonian parametres were obtained. 相似文献
17.
The magnetic hyperfine splitting frequencies of187WFe,182Re(j
π=2+)Ni,183ReNi,186ReNi,186ReFe and203PbFe in a zero external magnetic field have been determined by the NMR-ON method at about 7 mK as 225.56(6), 130.9(1), 98.17(4),
136.6(4), 1007.0(3) and 58.43(3) MHz, respectively. With the knowng-factors ofg(186Re, 1−)=1.739(3) andg(203Pb, 5/2−)=0.27456(20), the following hyperfine fields were deduced:B
HF(186ReNi)=−103.05(35) kG;B
HF(186ReFe)=−759.7(13) kG;B
HF(203PbFe)=+279.18(25) kG. Taking hyperfine anomalies into account, theg-factor of183Re was deduced as |g(183Re, 5/2+)|=1.267(6). With the assumption of Knight shift factorK=0, theg-factors of182Re and187W and the hyperfine field of187WFe were determined as |g(182Re, 2+)|=1.63(5), |g(187W, 3/2−)|=0.414(10) andB
HF(187WFe) =−714(18) kG. The large hyperfine anomaly was deduced to be183W Δ187W =−0.124(22). 相似文献
18.
Corrections of order α
5 and α
6 to the hyperfine structure of S- and P-wave energy levels of the muonic-helium ion are calculated. Electron-vacuum-polarization effects, corrections for the nuclear
structure, and recoil effects are taken into account. The numerical values obtained for respective hyperfine splitting, −1334.73
meV (1S), −166.64 meV (2S), −58 712.90 μeV (2P
1/2), and −24 290.69 μeV (2P
3/2), can be viewed as a reliable estimate for a comparison with experimental data, and the hyperfine-structure interval of Δ12 = 8ΔE
hfs(2S) − ΔE
hfs(1S) = 1.59 meV can be used to test QED predictions. 相似文献
19.
The paramagnetic hyperfine splitting of Ir4+ (5d5) in K2IrCl6 diluted into diamagnetic K2PtCl6 has been observed at 4.2 K and Ir∶Pt ratios of 1∶10 and 1∶25. In the latter case a narrow paramagnetic pattern with a hyperfine
coupling constant ofA=−13.1(2) mm/s was observed, but both samples also exhibit a single Ir4+ line typical for fast relaxation, either because of macroscopic inhomogeneities in the Ir distribution or because part of
the Ir spins are still coupled to nearest Ir neighbours. 相似文献
20.
Single crystal E.P.R. and cobalt ENDOR measurements on N,N′-ethylenebis(acetylacetonatiminato)Co(II), Coacacen, diluted in Niacacen·1/2 H2O are reported. Forbidden Δm Co = 1,2 transitions in the E.P.R. spectra have been observed. The g-tensor (E.P.R.) and the cobalt hyperfine and quadrupole tensors (ENDOR) have been determined. The g- and cobalt hyperfine tensors are discussed. They support the |2 A 2,yz? groundstate proposed for four coordinated low-spin Schiff base complexes of cobalt(II). The measured quadrupole coupling is also compatible with a |2 A 2,yz? groundstate, if anisotropic contraction of the cobalt 3d orbitals is taken into consideration. 相似文献