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

Abstract

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

High-spin Iron Complexes

“…Goldanskii etal. However, a counter-claim by Housley et al [49] refutes their results on the grounds that no allowance was made for the polarisation dependence of the molecular absorption cross-sections, and therefore the calculated areas for y-ray directions not parallel to the c axis are incorrect. A substantial anisotropy was claimed to be derived from the angular variation of the line intensities of the quadrupole doublet.…”

Nuclear level mixing-induced interference in FeCO3

“…In a pure single crystal the principal axis of the axially symmetrical electric field gradient (efg) then coincides with this symmetry axis, which will be referred to as the c axis. Natural siderite, however, is usually impure, with impurities quoted up to 17% [5][6][7][8][9][10][11], mainly Mg and Mn, possibly Ca and Zn. All of them are chemically equivalent to Fe.…”

“…Goldanskii et al [18] first reported a highly anisotropic f , which was explained as the Goldanskii-Karyagin effect. This was later refuted by the work of Housley et al [8,19], which correctly included the polarization dependence of the absorption lines. The most recent values of the Lamb-Mössbauer factor in FeCO 3 are f k c = 0.72(2) and f k⊥c = 0.75(2) (at 300 K) [11], which confirm the lack of spatial anisotropy.…”

“…Due to the absence of the second doublet in the parallel geometry, the splitting of the first doublet is taken as a reference. From the values for v 1 and v 3 a value for β e for both geometries is calculated according to equation (8). They are shown in the upper left part of figure 6.…”

“…Thirdly, the areas of the doublets remain more or less constant in this low-temperature interval. Because the area of a Mössbauer absorption line depends on the effective thickness T e , the angle of incidence θ and the magnetic quantum numbers of the levels involved (see, e.g., [8]), it is expected that this value is indeed temperature-independent.…”