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Mossbauer resonant isotope

Mossbauer resonance of Zn to study the influence of the gravitational field on electromagnetic radiation. A Ga ZnO source (4.2 K) was used at a distance of 1 m from an enriched ZnO absorber (4.2 K). A red shift of the photons by about 5% of the width of the resonance line was observed. The corresponding shift with Fe as Mossbauer isotope would be only 0.01%. The result is in accordance with Einstein s equivalence principle. Further gravitational red shift experiments using the 93.3 keV Mossbauer resonance of Zn were performed later employing a superconducting quantum interference device-based displacement sensor to detect the tiny Doppler motion of the source [66, 67]. [Pg.262]

Table 7.8 Summary of results obtained for the four Os Mossbauer transitions studied. The absorber thickness d refers to the amount of the resonant isotope per unit area. The estimates of the effective absorber thickness t are based on Debye-Waller factors / for an assumed Debye temperature of 0 = 400 K. For comparison with the full experimental line widths at half maximum, Texp, we give the minimum observable width = 2 S/t as calculated from lifetime data. Table 7.8 Summary of results obtained for the four Os Mossbauer transitions studied. The absorber thickness d refers to the amount of the resonant isotope per unit area. The estimates of the effective absorber thickness t are based on Debye-Waller factors / for an assumed Debye temperature of 0 = 400 K. For comparison with the full experimental line widths at half maximum, Texp, we give the minimum observable width = 2 S/t as calculated from lifetime data.
Lamb-Mossbauer factor of the absorber, the number of resonant isotope species... [Pg.313]

In Mossbauer spectroscopy of 57Fe, the radiation is specific for the 57Fe which eliminates the complications caused by the presence of other atoms. Most elements do not have a suitable isotope available for Mossbauer spectroscopy. Because iron is of such paramount importance in the molecules of life it is indeed fortunate that 57Fe exhibits such a good Mossbauer resonance. If a biological molecule contains iron, it is almost... [Pg.60]

The nuclide with the lowest mass for which a Mossbauer resonance has been recorded is °K. This isotope has a natural abundance of 0-012% and is itself radioactive with a half-life = 1-26 X 10 y. The 29-4-keV first excited state is not populated by any radioactive parent, but can be reached during the course of nuclear reactions on the predominant potassium isotope K. Two basic methods have been used a ([Pg.433]

Gadolinium is unique in having eight known MOssbauer resonances in six isotopes ... [Pg.558]

Corrosion of Metals. Corrosion phenomena of iron, cobalt, tin, and their alloys have been investigated by a variety of Mossbauer techniques by the transmission and scattering methods and by the emission technique in which the specimen under study is doped with a Mossbauer source isotope (e.g., Co) and measured against a single-line resonant... [Pg.506]

In Mbssbauer spectroscopy the y-rays from the source are passed through the absorber to a detector, as shown in Fig. 1. Transmission of the y-rays is reduced because of resonant absorption in the absorber followed by re-emission over a 4tx solid angle. When the Mossbauer active isotope in the somce exists in a different chemical environment to the same isotopic species in the absorber then the energy of the y-ray, emitted by the somce will differ from that required for... [Pg.520]

It is important to realize that isomer shifts (in mm/s) cannot be compared for different resonances. Not only does ot vary widely (and can have a positive or negative sign) but the transition energy q so enters [e.g. in eq. (19)]. For any given isotope the isomer shifts are commonly referred to a certain compound representing the zero point of the isomer shift scale. For example, in Np the intermetallic NpAl2 serves as reference. For other Mossbauer resonances see Cohen and Kalvius (1970). [Pg.552]

For the high-energy transitions ( Gd, Yb, Np, Am) cooling of the source to liquid He temperatures (or thereabout) is essential. Even with this condition fulfilled it is difficult to obtain good spectra for absorber temperatures much above lOOK. This is a most serious restriction. Especially for Yb the use of isotopically enriched samples can be helpful. For Eu and Dy the / factors are high. The source can conveniently be kept at room temperature and absorbers may be heated well above room temperature, quite analogous to the case of the standard Mossbauer resonance, Fe. [Pg.565]

In addition to the preparation of a solid sample, one should also notice that the content of iron as well as the natural abundance of its Mossbauer isotope Fe is manifestly low. Thus, the intensity of Mossbauer resonance may have difficulty in meeting the requirement since the resonance absorption cross-section is relatively low. More often, samples containing iron have to be enriched with the isotope If the samples are purified from bacteria or cells in... [Pg.144]

A typical device for accumulating the Mossbauer spectrum is the multichannel analyser, where the count rate is a function of a definite value of the Doppler velocity. The count rate is normalized relative to the off-resonance count rate. Hence, for transmission-mode Mossbauer spectroscopy relative intensities are always less than unity (or 100%). In Mossbauer scattering experiments relative intensities always exceed 100% and can reach several hundred percent in the case of electron detection from samples with a high abundance of the resonant isotope. It is most often that the -y ,ax value corresponds to the first channel and the +y ,ax value to the last channel. The quality of a Mossbauer spectrometer is determined by how accurately the modulation of the y-quanta energy follows the chosen mode of movement. [Pg.154]

Resonance Raman studies of the recombinant proteins showed vibrational bands at the 200-430 cm region characteristic of iron-sulfur clusters (124). Most interestingly, on Fe and O isotope sensitive band was detected at 801 cm which could be attributed to either a Fe(IV)=0 species or a monobridged Fe-O-Fe structure. This observation, together with Mossbauer analysis, which indicated a mixed N, 0, and S ligand environment for cluster 2, suggests a Fe-O-Fe or Fe=0 unit as part of the structure for cluster 2. [Pg.380]

The Mossbauer effect, discovered by Rudolf L. Mossbauer in 1957, can in short be described as the recoil-free emission and resonant absorption of gamma radiation by nuclei. In the case of iron, the source consists of Co, which decays with a half-life of 270 days to an excited state of Fe (natural abundance in iron 2%). The latter, in turn, decays rapidly to the first excited state of this isotope. The final decay generates a 14.4 keV photon and a very narrow natural linewidth of the order of nano eV. [Pg.147]

Fig. 2.1 Nuclear resonance absorption of y-rays (Mossbauer effect) for nuclei with Z protons and N neutrons. The top left part shows the population of the excited state of the emitter by the radioactive decay of a mother isotope (Z, N ) via a- or P-emission, or K-capture (depending on the isotope). The right part shows the de-excitation of the absorber by re-emission of a y-photon or by radiationless emission of a conversion electron (thin arrows labeled y and e , respectively)... Fig. 2.1 Nuclear resonance absorption of y-rays (Mossbauer effect) for nuclei with Z protons and N neutrons. The top left part shows the population of the excited state of the emitter by the radioactive decay of a mother isotope (Z, N ) via a- or P-emission, or K-capture (depending on the isotope). The right part shows the de-excitation of the absorber by re-emission of a y-photon or by radiationless emission of a conversion electron (thin arrows labeled y and e , respectively)...
Mossbauer spectra of Dy, Sb, and other isotopes may show resonances at... [Pg.33]

For nuclear y-resonance absorption to occur, the y-radiation must be emitted by source nuclei of the same isotope as those to be explored in the absorber. This is usually a stable isotope. To obtain such nuclei in the desired excited meta-stable state for y-emission in the source, a long-living radioactive parent isotope is used, the decay of which passes through the Mossbauer level. Figure 3.6a shows such a transition cascade for Co, the y-source for Fe spectroscopy. The isotope has a half-life time //2 of 270 days and decays by K-capmre, yielding Fe in the 136 keV excited state ( Co nuclei capmre an electron from the K-shell which reduces the... [Pg.34]

Mossbauer nuclei per square centimetre, the Debye-Waller factor/a of the absorber material, and the resonance cross-section Gq of the Mossbauer isotope. For a multiline spectrum, the result must be split into separate values for each line, which are obtained by weighting t with the relative transition probability of each line. [Pg.46]

There are two iridium isotopes, ir and Ir, suitable for Mossbauer spectroscopy. Each of them possesses two nuclear transitions with which nuclear resonance absorption has been observed. Figure 7.58 (from [266]) shows the (simplified) nuclear decay schemes for both iridium Mossbauer isotopes the Mossbauer transitions are marked therein with bold arrows. The relevant nuclear data known to date for the four Mossbauer transitions are collected in Table 7.1 at the end of the book. [Pg.320]

The first Mossbauer measurements involving mercury isotopes were reported by Carlson and Temperley [481], in 1969. They observed the resonance absorption of the 32.2 keV y-transition in (Fig. 7.87). The experiment was performed with zero velocity by comparing the detector counts at 70 K with those registered at 300 K. The short half-life of the excited state (0.2 ns) leads to a natural line width of 43 mm s Furthermore, the internal conversion coefficient is very large (cc = 39) and the oi pj precursor populates the 32 keV Mossbauer level very inefficiently ( 10%). [Pg.373]

In 1971, Walcher [326] succeeded in observing a resonance effect of about 0.6% in as a function of the Doppler velocity using a TI2O3 source and an enriched (81% ° Hg) HgO absorber at 4.2 K. The half-width turned out to be Fexp = 76 (10) mm s corresponding to a lower limit of the half-life of fi/2 > 0.1 ns. It is clear that the properties of the ° Hg Mossbauer isotope do not render it an interesting isotope from a chemical point of view. [Pg.373]

Potential Mossbauer isotopes for nuclear resonance scattering, which are within the spectral reach of synchrotron radiation sources, are summarized in Table 9.5 [118-120], and the synchrotron radiation sources which provide dedicated beam lines for specific Mossbauer isotopes are listed in Table 9.6 (adopted from [85]). [Pg.534]


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