Mossbauer spectroscopy quadrupole interaction

Equation (4.15) would be extremely onerous to evaluate by explicit treatment of the nucleons as a many-particle system. However, in Mossbauer spectroscopy, we are dealing with eigenstates of the nucleus that are characterized by the total angular momentum with quantum number 7. Fortunately, the electric quadrupole interaction can be readily expressed in terms of this momentum 7, which is called the nuclear spin other properties of the nucleus need not to be considered. This is possible because the transformational properties of the quadrupole moment, which is an irreducible 2nd rank tensor, make it possible to use Clebsch-Gordon coefficients and the Wigner-Eckart theorem to replace the awkward operators 3x,xy—(5,yr (in spatial coordinates) by angular momentum operators of the total... 

C. P. Slichter s textbook on magnetic resonance [4] may be recommended for further reading. It presents a very educational introduction into this issue of operator equivalence. A comprehensive, elaborate article on quadrupole interaction in Mossbauer spectroscopy is provided by H. Spiering in [5],... 

Two other publications on Ir (73 keV) Mossbauer spectroscopy of complex compounds of iridium have been reported by Williams et al. [291,292]. In their first article [291], they have shown that the additive model suggested by Bancroft [293] does not account satisfactorily for the partial isomer shift and partial quadrupole splitting in Ir(lll) complexes. Their second article [292] deals with four-coordinate formally lr(l) complexes. They observed, like other authors on similar low-valent iridium compounds [284], only small differences in the isomer shifts, which they attributed to the interaction between the metal-ligand bonds leading to compensation effects. Their interpretation is supported by changes in the NMR data of the phosphine ligands and in the frequency of the carbonyl stretching vibration. 

We have learned from the preceding chapters that the chemical and physical state of a Mossbauer atom in any kind of solid material can be characterized by way of the hyperfine interactions which manifest themselves in the Mossbauer spectrum by the isomer shift and, where relevant, electric quadrupole and/or magnetic dipole splitting of the resonance lines. On the basis of all the parameters obtainable from a Mossbauer spectrum, it is, in most cases, possible to identify unambiguously one or more chemical species of a given Mossbauer atom occurring in the same material. This - usually called phase analysis by Mossbauer spectroscopy - is nondestructive and widely used in various kinds of physicochemical smdies, for example, the studies of... 

Besides NQR spectroscopy and the study of nuclear quadrupole interaction effects in broad-line NMR spectroscopy, paramagnetic electron resonance 6°1, Mossbauer spectroscopy, and the study of perturbed angular correlation of y-rays, are suitable methods for studying nuclear quadrupole interactions in solids. Indirect methods are also available for acquiring information about the nuclear quadrupole couplinjg constant from the liquid state (particularly NMR spectroscopy in liquids and in liquid crystals in some cases gives information about this constant). By microwave spectroscopy, the nuclear quadrupole interaction may be studied in the gaseous phase (see the paper by Zeil). We shall deal here only with the aspect of NQR spectroscopy in solids since this method has the broadest applicability to chemical problems in comparison with the other methods mentioned. 

Mossbauer spectroscopy senses the hyperfine interactions, which are present at the nucleus of the Mossbauer isotope. The electrical monopole interaction causes the isomer shift and the electric quadrupole interaction leads to the quadrupole splitting, which in the case of Fe causes a two-line Mossbauer pattern. The magnetic dipole interaction leads to a magnetically split six-line pattern (Figure 4). In the following text, these interactions and their deduction from Mossbauer spectra will be discussed. 

The recently synthesized Au(V) complex fluorides of the form A AuFjwith A = Xe2F, XeRJ, and Cs have been studied by Mossbauer spectroscopy with the 77.3 keV gamma resonance of Au. The values obtained for isomer shift and electric quadrupole interaction are in harmony with the assigned oxidation state Au(V), as well as with the octahedral shape of the AuFj anion. 

Rancourt DG (1994a) Mossbauer spectroscopy of minerals 1. Inadequacy of Lorentzian-line doublets in fitting spectra arising from quadrupole sphtting distributions. Phys Chem Minerals 21 244-249 Rancourt D(3 (1994b) Mossbauer spectroscopy of minerals 11. Problem of resolving cis and trans octahedral Fe sites. Phys Chem Minerals 21 250-257 Rancourt DG (1998) Mossbauer spectroscopy in clay science. Hyper Interact 117 3-38 Rancouit DG, Dang MZ, Lalonde AE (1992) Mossbauer spectroscopy of tetrahedral Fe in trioctahedral micas. Am Mineral 77 34-43... 

The existence of an electric quadrupole interaction is one of the most useful features of Mossbauer spectroscopy. The theory is closely related to that used in nuclear quadrupole resonance spectroscopy [14, 15). Any nucleus with a spin quantum number of greater than / = 4 has a non-spherical charge distribution, which if expanded as a series of multipoles contains a quadrupole term. The magnitude of the charge deformation is described as the nuclear quadrupole moment Q, given by... 

The scope of the conference is less restrictive than the title implies the conference deals with all aspects of quadrupole interactions, including NMR, Mossbauer, and other spectroscopies. Meetings occur in odd years world wide. 

---