ELECTRIC QUADRUPOLE INTERACTION OF 178Hf IN NONCUBIC METALS

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Valence Determination in EuM2X2\mathrm{EuM_2X_2} Compounds : LIII\mathrm{L_{III}} -Edge Versus Mössbaur Isomer Shif

A comparative study by Eu-LIII X-ray absorption and $^1$$^5$$^1$Eu-Mossbauer spectroscopy is presented for the EUPd $_2$$_-$$_x$AU$_x$S$_2$ series. Possible ways to distinguish between mixed-valent behavior and final-state effects in the LIII-edge spectra are discussed

VALENCE DETERMINATION IN EuM2X2 COMPOUNDS : LIII-EDGE VERSUS MÖSSBAUER ISOMER SHIFT

A comparative study by Eu-LIII X-ray absorption and 151Eu-Mössbauer spectroscopy is presented for the EuPd2-xAuxSi2 series. Possible ways to distinguish between mixed-valent behaviour and final-state effects in the LIII-edge spectra are discussed

Temperature and pressure dependence of the mean valence of Eu in EuNi<SUB>2</SUB>P<SUB>2</SUB>

The effects of temperature and pressure on the mean valence &#957;&#x0305; of Eu in EuNi2P2 were studied by M&#246;ssbauer spectroscopy. The observed variation of &#957;&#x0305; with pressure proves the strongly mixed-valent state of Eu in this compound even at liquid-helium temperature

Effects of chemical substitution on the valence of Eu in EuNi<SUB>5</SUB>

The effects of substituting Eu by other rare-earth elements on the valence of Eu in EuNi5 was studied using the 21.7-keV M&#246;ssbauer resonance of 151Eu. The experimental results support the view of a dominant influence of the local electronic structure on the valence of Eu as compared to the unit-cell volume

Valence state of Eu and unit-cell volume anomaly in EuPd<SUB>2</SUB>P<SUB>2</SUB>

M&#246;ssbauer isomer shift and magnetic susceptibility measurements clearly prove the divalent nature of Eu in EuPd2P2, a new compound recentlu classified as intermediate valent on grounds of its unit-cell volume anomaly. We explain the relatively small positive deviation in unit-cell volume from the systematic trend in trivalent REPd2P2 compounds as a consequence of strong chemical bonding between the divalent Eu ion and the ligands

Critical evaluation of Eu valences from LIII\mathrm{L_{III}} -edge x-ray-absorption and Mössbauer spectroscopy of EuNi2Si2−xGex\mathrm{EuNi_2Si_{2-x}Ge_x}

In the quasiternary $EuNi_2Si_{2−x}Ge_x$ system most of the Eu ions exhibit an intermediate-valence character, depending on the number of Si neighbors and the temperature. A detailed study of $EuNi_2Si_{0.5}Ge_{1.5}$ by Eu L$_{III}$ x-ray-absorption and $^{151}Eu$ Mössbauer spectroscopy reveals a sharp temperature-induced valence change, which is more complete than in any other Eu system. A linear correlation between the mean Eu valence, (L$_{III}$), derived from L$_{III}$-edge measurements, and the mean Mössbauer isomer shift is only observed if a variation of the recoil-free fraction at the different Eu sites is taken into account. The Eu L$_{III}$ spectra of $EuNi_2Ge_2$, in which the Eu is divalent according to Mössbauer and magnetization measurements, result in v(L$_{III}$)=2.15, which is similar to other divalent intermetallic Eu systems. This observation is attributed to final-state effects due to covalency. The magnetic susceptibility of $EuNi_2Si_{0.5}Ge_{1.5}$ is in accord with the intermediate-valence character of this compound, which orders ferromagnetically at 25 K

MÖSSBAUER STUDY OF SbF5- DOPED POLYACETYLENE

Nous avons étudié la spectroscopie Mössbauer du 121Sb du polyacétylène dopé au SbF5 avec des concentrations de 0,1 à 8,4 % molaire. Les spectres révèlent la présence de molécules de SbF3, SbF5 et SbF-6. A partir des intensités relatives des spectres, nous avons pu déterminer les fractions relatives des trois espèces en fonction de la concentration en dopant.SbF5-doped polyacetylene was studied on samples with dopant concentrations ranging from 0.1 to 8.4 mol%, using 121Sb Mössbauer spectroscopy. The spectra reveal the presence of SbF3, SbF5, and SbF-6, respectively. From the relative intensities of the well-separated subspectra we could determine the relative fractions of the three molecular species as a function of dopant concentration