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1.
The Mössbauer spectra of Fe57 in n- and p-type silicon and germanium have been studied. In silicon, iron produced by the decay of cobalt has a dominant, unsplit absorption at − 0.0012 ± 0.0003 cm/sec doppler velocity relative to potassium ferrocyanide. No difference in isomer shift has been observed between n- and p-type silicon, indicating that the iron tested was electrically inactive. The spectrum of substitutional Fe57 has been identified with an absorption at + 0.054 ± 0.004 cm/sec showing less than 3 Mc/sec electric quadrupole splitting. The spectrum of iron produced by the decay of cobalt in germanium is a doublet with an isomer shift of + 0.036 ± 0.001 cm/sec and with a quadrupole splitting of 5 Mc/sec. It is assumed that this splitting is due to the asymmetrical positions of the Fe0 and Fe1− atoms in the germanium lattice. No differences in isomer shift or quadrupole splitting were observed between iron in n- and p-type germanium, indicating that the iron is electrically inactive.  相似文献   

2.
The effect of pressure on the Mössbauer isomer shift and quadrupole splitting was studied with the 77 keV resonance of197Au in the Au(I)-cyanides AuCN and KAu(CN)2 at 4.2 K under pressures up to 80 kbar. We observe an increase of the electron density and a decrease of the absolute value of the electric field gradient at the Au nuclei in both compounds with pressure. This variation is different from the correlation that has been established for these parameters within the chemical series of Au(I) compounds at ambient pressure. It indicates that the-bonding increases strongly under pressure. X-ray diffraction studies on AuCN under pressures up to 115 kbar together with investigations of the Goldanskii-Karyagin-effect on AuCN at ambient pressure support the previous assumption that the sign of the electric field gradient at the Au(I) sites is negative.  相似文献   

3.
The 77.3 keV Mössbauer transition of197Au was used to study the hyperfine interactions and recoilfree fractions of dilute Au impurities in Zn and Cd single crystals at 4 K. Mössbauer sources were prepared by ion implantation of197mHg/197Hg at ambient temperature. From the quadrupole splittings the electric field gradients $$\begin{gathered} eq(Au\underline {Cd} ) = + 11.7(6) \times 10^{17} v/cm^2 and \hfill \\ eq(Au\underline {Zn} ) = ( + )15.0(2.5) \times 10^{17} v/cm \hfill \\ \end{gathered} $$ were determined. The electric field gradients as well as the isomer shifts are in good agreement with the systematics of other impurity host systems. The recoilfree fractions agree with estimates using the mass corrected Debye temperatures of the host lattice.  相似文献   

4.
We present a detailed Mössbauer study of a series of Au and Pt particles in the size range from 1 to 17 nm. All measured spectra can be explained consistently with a refined model, in which the Mössbauer isomer shift varies in the inner core of a small metallic particle due to size effects. The large surface/volume ratio makes surface effects, like screening of considerable importance and even the so-called quantum-size effect may have an influence. The size evolution of the electronic properties of the particles is also discussed.  相似文献   

5.
The effect of pressure on the Mössbauer isomer shift and quadrupole splitting was studied with the 77 keV resonance of197Au in the Au(I)-cyanides AuCN and KAu(CN)2 at 4.2 K under pressures up to 80 kbar. We observe an increase of the electron density and a decrease of the absolute value of the electric field gradient at the Au nuclei in both compounds with pressure. This variation is different from the correlation that has been established for these parameters within the chemical series of Au(I) compounds at ambient pressure. It indicates that the-bonding increases strongly under pressure. X-ray diffraction studies on AuCN under pressures up to 115 kbar together with investigations of the Goldanskii-Karyagin-effect on AuCN at ambient pressure support the previous assumption that the sign of the electric field gradient at the Au(I) sites is negative.  相似文献   

6.
7.
A comparative study of normal human, rabbit and pig oxyhemoglobins and oxyhemoglobin from patients with chronic myeloleukemia and multiple myeloma using Mössbauer spectroscopy with a high velocity resolution demonstrated small variations of the 57Fe quadrupole splitting and isomer shift. These variations may be a result of small structural differences in the heme iron stereochemistry of various hemoglobins.  相似文献   

8.
《Nuclear Physics A》1968,111(2):371-384
The electron spectrum arising from internal conversion in 169Tm has been examined as a function of the chemical environment. The 169Er ions were imbedded after passage through an isotope separator into a variety of targets including tungsten metal, WO3 and Tm2O3. The electron spectra were measured with a double-focussing electron spectrometer. The relative intensities of the converted electrons with the exception of the outermost PI shell were insensitive to the chemical media. The analysis gave MI 100, MII 37 ±1, RmIII 38±1, MV 0.9 ± 0.2, MV 1.0±0.2, NI 22.1±0.6, NII 6.4±0.3, NIII 7.6±0.2, NIV,V 0.20±0.02, OI 3.7±0.1, OII, III 2.08±0.06. This is in agreement with theory based on an M1 transition with 0.108% E2 admixture. The intensity of the PI shell, however, was found to be dependent on the chemical surroundings. The ratio of PI/OI intensities were 0.056±0.007, 0.035±0.006, and 0.030±0.006, respectively, for W, Tm2O3 and WO3. This indicates that the PI conversion in the oxides is 38% (Tm2O3) and 46% (WO3) lower than in the metal. The internal conversion coefficients were compared with electron densities obtained from relativistic wave functions for Tm and Tm ions. From this comparison, it was possible to estimate the changes in electron densities at the nucleus. A discussion is made of the importance of these electron density measurements in evaluating Mössbauer isomer shifts. The transition energy is found to be 8.401±0.008 keV.  相似文献   

9.
The magnetite/maghemite content within iron oxide nanoparticles can be determined using the mean isomer shift (\(\overline {\delta }\)). However, accurate characterisation of the composition is limited by the uncertainty associated with \(\overline {\delta }\). We have identified four independent sources of uncertainty and developed a quantitative expression for the uncertainty budget. Sources of uncertainty are categorised as follows: that from the fitting of the Mössbauer spectrum (σ fit), that of the calibration of the α-Fe reference spectrum (σ cal), thermal corrections to the spectrum due to second order Doppler shift (SODS) (σ Δδ ) and other experimental errors (σ err). Each contribution is discussed in detail using 57Fe Mössbauer spectra obtained from an iron oxide nanoparticle system at temperatures between 16 K and 295 K on different spectrometers in two different laboratories.  相似文献   

10.
The chemical state of gold adsorbed on activated carbon from solutions of KAu(CN)2 has been studied by197Au Mössbauer spectroscopy as a function of the pH and concentration of the solution, the loading of the carbon, and the drying conditions of the samples. On freshly prepared specimens Au(CN) 2 ? is always the dominant species. Drying leads to the formation of other forms of gold, mainly in samples loaded from strongly acidic media. An oligomeric form of AuCN is, however, also formed when samples loaded at high pH values are dried at temperatures around 100°C.  相似文献   

11.
In this review some aspects are shown of the role of Mössbauer spectrometry in the understanding and the development of catalysts for the hydrogenation of CO, such as Fe/ZrO2 for the production of light olefins, Fe/SiO2 to study the formation of iron pentacarbonyl and Co/Al2 O3. Applying this Fischer-Tropsch process fuels of high purity, chemical feedstocks and special chemicals by leading a mixture of CO and H2 over an iron (cobalt) based catalyst are produced.  相似文献   

12.
Radioactive125I was ion-implanted into 7 different metal matrices. Al, Au, In, Pt, Sn, Te and Zn, and internal conversion and Mössbauer spectra associated with the 35.46 keV M1 transition of125Te were measured for the same samples. A value R/R=(0.853±0.115)×10–4 was derived for the relative difference of the nuclear charge radius for the 35.46 keV M1 transition of125Te.  相似文献   

13.
《Physica B+C》1977,86(3):366-368
The probabilities for recoilles resonant absorption of 77.3 keV λ-rays by 197Au and 23.8 keV λ-rays by 119Sn in matrices of gold, palladium and platinum have been calculated in the temperature ranges 4.2–100 K and 80–400 K, respectively. The calculated results show a good agreement with the experimental data.  相似文献   

14.
15.
Acetylene hydrochlorination catalysts consisting of activated carbon impregnated with a solution of HAuCl4·xH2O in aqua regia have been studied by197Au Mössbauer spectroscopy. The relative amounts of AuCl 4 ? , of Au(0), and of an Au(J) species formed under certain process conditions were determined quantitatively. Deactivation of the catalyst at low and high temperatures was shown to be due to different mechanisms, and the reactivation of the catalyst by Cl2 gas was studied.  相似文献   

16.
We have investigated the structures and electronic states of a series of glutathionate-protected Au clusters, Au n (SG) m with n = 10 ? ~55, using 197Au Mössbauer spectroscopy, which allows us to probe the local environment of the constituent Au atoms via isomer shift (IS) and quadrupole splitting (QS). The spectral profile abruptly changes on going from Au22(SG)17 to Au25(SG)18, then it smoothly changes to that of Au~55(SG)m. However, the spectral profile dramatically changes on going from Au~55(SG)m to the dodecanethiolate-protected Au cluster with average diameter of 2 nm. The 197Au Mössbauer spectra of glutathionate-protected Au clusters and dodecanethiolate-protected Au clusters were successfully analyzed on the basis of the structure and electronic state of Au25(SG)18.  相似文献   

17.
A historical outline is given of the discovery of recoilless nuclear resonance absorption of γ-radiation, also called the Mössbauer (M-) effect.  相似文献   

18.
The temperature dependence of the intensity of the Mössbauer line and the shift of its centre on passing through the points of phase transitions was studied. Both quantities exhibit discontinuity at transitions of the first kind while only the shift of the line centre does so at transitions of the second kind. The possibility of using the Mössbauer effect for the exact localization or even classification of phase transitions is shown.  相似文献   

19.
A hypothesis based on the literature data on the Mössbauer, structural, and magnetic parameters of different iron oxidation states is proposed, according to which changes in the electronic configuration of an iron ion that are caused by an electron (or a change of iron oxidation state by one) can vary the isomer shift by a constant (~0.33 mm s?1), if it is assumed that the structure of the iron’s valent shell and iron spatial environment remain unchanged.  相似文献   

20.
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