Temperature dependence of Mossbauer

Fig. 4. Temperature dependence of Mossbauer parametrs ofe frozen solution of (a) Fe Cl2, (b) Fe (NH4)2 (S04)2, (c) FeS04, and (d) Fe (C104)2 71 line width. / intensity of the absorption lines. AEq-. quadrupole splitting. [Taken from Ref. (54)]...

Figure 3. Temperature dependence of Mossbauer parameters of a ferrous Nafion deduced from a one-site fit of spectra in Figure 2a.

The temperature dependence of Mossbauer parameters of celadonite was charac-... 

The temperature dependence of MOssbauer parameters can be very useful in qualitative analysis. As the temperature dependence of the different spectrum components is usually different, measuring the same sample at different temperatures may help distinguish between species whose fingerprints are similar under standard conditions (i.e., at room temperature in the given instance) but different at lower or higher temperatures. 

Fig. 33. (a) Temperature dependence of Mossbauer spectra for 6 ADy/33 Ape (b) temperature dependence of the average angle between the film tli sp " direction of Fe estimated from the Mflssbauer spectra... 

The recoil-free fraction depends on the oxidation state, the spin state, and the elastic bonds of the Mossbauer atom. Therefore, a temperature-dependent transition of the valence state, a spin transition, or a phase change of a particular compound or material may be easily detected as a change in the slope, a kink, or a step in the temperature dependence of In f T). However, in fits of experimental Mossbauer intensities, the values of 0 and Meff are often strongly covariant, as one may expect from a comparison of the traces shown in Fig. 2.5b. In this situation, valuable constraints can be obtained from corresponding fits of the temperature dependence of the second-order-Doppler shift of the Mossbauer spectra, which can be described by using a similar approach. The formalism is given in Sect. 4.2.3 on the temperature dependence of the isomer shift. 

In addition to the four detectors used to detect backscattered radiation from the sample, there is a fifth detector to measure the transmission spectrum of the reference absorber (a- Fe, a- Fe203, Fc304 see Fig. 3.16). Sample and reference spectra are recorded simultaneously, and the known temperature dependence of the Mossbauer parameters of the reference absorber can be used to give a measurement of the average temperature inside the SH, providing a redundancy to measurements made with the internal temperature sensor (see Sect. 3.3.4). 

Fig. 4.2 Temperature dependence of the isomer shift due to the second-order Doppler shift, sod- The curves are calculated for different Mossbauer temperatures 0m by using the Debye model whereby the isomer shift was set to (5 = 0.4 mm s and the effective mass to Meff =100 Da, except for the dashed curve with Meff = 57 Da...

Fig. 6.19 Temperature dependence of the total magnetic field, 5tot, for the three sextets in the Mossbauer spectra of Mno.25Zno.75Fe204, shown in Fig. 6.18. (Adapted with permission from [84] copyright 2003 by Elsevier)...

With the observed temperature shift data for (dSldT)p and calculated (within the framework of the Debye model) numbers for the temperature shift of SOD and with the known thermal expansion coefficient as well as results from Ta Mossbauer experiments under pressure, the authors [191] were able to evaluate the true temperature dependence of the isomer shift, (dSisIdT) as —33 10 " and —26 10 " mm s degree for Ta and W host metal, respectively. 

Another study of the temperature dependence of the 6.2 keV Mossbauer resonance of Ta has been carried out by Salomon et al. [197] for sources of WAV metal and W/Ta metal in the temperature range from 15 to 457 K. In more recent investigations, Salomon et al. [198] have extended such studies of the temperature behavior of the 6.2 keV Mossbauer transition of Ta in tantalum metal to temperatures up to 2,300 K which has been the highest temperature range for any Mossbauer study so far. 

Mossbauer spectroscopy with started only in 1965, when Harris et al. [322] measured the Mossbauer absorption spectra of the 99 keV transition of Pt in platinum metal as a function of temperature (between 20 and 100 K) and of absorber thickness and derived the temperature dependence of the Debye-Waller factor. 

The long-wavelength IR spectra of trigonal prismatic technetium clusters and a number of unusual physico-chemical properties of the clusters with ferrieinium cations [108] support the latter assumption. The discovered properties of the clusters with ferrieinium cations may be accounted for by the formation of the conductivity bands and, probably, hard-fermion bands in these compounds by the 5s(5p)-AO s of technetium atoms and 4s(4p)-AO s of the iron atoms. The formation of these bands may be supported by the following facts the ESR spectra of these compounds with geft close to that of a free electron temperature independent conductivity and an unusual temperature dependence of the Mossbauer and X-ray photoelectron spectra [108]. 

The relaxation fits of the Mossbauer spectra of [Fe(HB(pz)3)2] yield [30] the temperature dependence of both the population of the iron(II) high-spin and low-spin states and the relaxation rate between these two states. The resulting population of the high-spin state has a striking resemblance to that of the magnetic moment shown in Fig. 1 and these populations provide clear support both for the spin-state crossover and for the difference in populations upon heating and cooling. 

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