Sign of the Nuclear Quadrupole Coupling Constants in Some Ionic Ferrous Compounds

Grant, R. W.; Wiedersich, H.; Muir, A. H.; Gonser, U.; Delgass, W. Nicholas

doi:10.1063/1.1727651

Cited by 68 publications

(20 citation statements)

References 14 publications

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“…The immediate iron environment in both cases is a distorted octahedron of oxygens so that the compound contains [Fe(H2 0)6]2+. The signs of the coupling constants have been confirmed as positive by the magnetic perturbation method [32], and the electronic excited states estimated assuming only one type of site [5,19]. Such measurements have been made [43], and indicate an 1 xy) ground state (positive e 2 qQ) and an asymmetry parameter of 1] = 0·1 for both the A and B sites.…”

Section: Fes04mentioning

confidence: 68%

“…The sign of eZqQ was also shown to be positive by using the applied magnetic field method [32]. The sign of eZqQ was also shown to be positive by using the applied magnetic field method [32].…”

Section: Feci2 ·4h20mentioning

confidence: 85%

“…The first experiments [40] used a single-crystal absorber and a polarised magnetic foil source. The intensities of the spectral components show that the coupling constant eZqQ is negative as required for a I zZ) state, and this sign has also been checked by the magnetic perturbation technique [32]. The quadrupole splitting is large (3'612 mm S-1 at 29 K [32]) because of the lack of appreciable state mixing.…”

Section: Iron(ii) Salts Of Oxyacids and Other Anionsmentioning

confidence: 95%

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High-spin Iron Complexes

Greenwood

Gibb

1971

Mössbauer Spectroscopy

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Section: Fes04mentioning

confidence: 68%

Section: Feci2 ·4h20mentioning

confidence: 85%

Section: Iron(ii) Salts Of Oxyacids and Other Anionsmentioning

confidence: 95%

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High-spin Iron Complexes

Greenwood

Gibb

1971

Mössbauer Spectroscopy

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“…Gibb [3] and Spiering and Vogel [4] re-determined the macroscopic efg of FCL at 300 K, each making thickness corrections including polarization. Gibb in addition used polarized source (i.e., magnetically perturbed) measurements and obtained e 2 qQ (= e Q Pẑẑ in the nomenclature of this paper; note that, throughout, we shall use the notation Tαα to denote a principal value of a matrix T) positive in agreement with Zory [1] and independent measurements of Grant et al [5]. Ono et al [6] also inferred a positive value from measurements below the Néel temperature.…”

Section: Introductionmentioning

confidence: 65%

Microscopic 57 Fe electric-field-gradient and anisotropic mean-squared-displacement tensors: ferrous chloride tetrahydrate

2010

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This paper reports the determination of the electric-field-gradient and mean-squared-displacement tensors in 57 Fe symmetry-related sites of1 Laue class in monoclinic FeCl 2 .4H 2 O at room temperature by single-crystal Mössbauer spectroscopy. Contrary to all previous work, the mean-squared-displacement matrix (tensor), , is not constrained to be isotropic resulting in the determination of physically meaningful estimates of microscopic (local) electric-field gradient (efg) and tensors. As a consequence of anisotropy in the tensor the absorber recoilless fractions are also anisotropic. As expected of a low-symmetry site, Laue class1 in this case, no two principal axes of the efg and tensors are coaxial, within the combined errors in the two. Further, no principal direction of the efg tensor seems related to bond directions in the unit cell. Within error, and in agreement with an earlier study of sodium nitroprusside, it appears that the tensor principal directions lie close to the crystallographic axes suggesting that they are determined by long wavelength (phonon) vibrations in the crystal rather than by approximate local symmetry about the 57 Fe nucleus. Concurrent with the Mössbauer measurements, we determined as part of a new X-ray structural determination, precise atomic displacement parameters (ADPs) leading to an alternative determination of the matrix (tensor). The average of the eigenvalues of the Mössbauer-determined exceeds that of the average of the X-ray-determined eigenvalues by a factor of around 2.2. Assuming isotropic absorber recoilless fractions leads to substantially the same (macroscopic) efg tensor as had been determined in earlier work. Taking 1 3 × the trace of the anisotropic absorber recoilless fractions leads to an isotropic value of 0.304 in good agreement with earlier single crystal studies where isotropy was assumed.

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“…The energy separation E z -E 1 is equal to ftu) x + fiw 2 , where o> x and oo 2 are the emitted complementary frequencies. Levels E 3 and E x have the same parity if the system has inversion symmetry, but the following discussion need not be limited to such systems. The existence of a virtual state E 2 inside the energy interval E 3 -E l is helpful for two-photon emission, but is not essential.…”

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confidence: 99%

Mössbauer Determination of the Debye-Waller Factor in Single-Crystal Absorbers

1968

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The equation which must be used to obtain the Debye-Waller factor/' from Mossbauer absorption measurements on single-crystal samples with resolved and hence generally polarized lines is given. The polarization terms for a crystal having the symmetry of siderite are explicitly presented and theoretical area ratios are compared with recently reported values calculated from a theory neglecting polarization. New experimental data indicate that/' 5=0.6 for all directions in siderite. PHYSICAL REVIEW LETTERS 3 JUNE 1968

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Sign of the Nuclear Quadrupole Coupling Constants in Some Ionic Ferrous Compounds

Cited by 68 publications

References 14 publications

High-spin Iron Complexes

High-spin Iron Complexes

Microscopic 57 Fe electric-field-gradient and anisotropic mean-squared-displacement tensors: ferrous chloride tetrahydrate

Mössbauer Determination of the Debye-Waller Factor in Single-Crystal Absorbers

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