Half Mossbauer spectroscopy

In studies of superparamagnetic relaxation the blocking temperature is defined as the temperature at which the relaxation time equals the time scale of the experimental technique. Thus, the blocking temperature is not uniquely defined, but depends on the experimental technique that is used for the study of superparamagnetic relaxation. In Mossbauer spectroscopy studies of samples with a broad distribution of relaxation times, the average blocking temperature is commonly defined as the temperature where half of the spectral area is in a sextet and half of it is in a singlet or a doublet form. 

Promethium is another poor candidate for chemical Mossbauer spectroscopy as it is not a naturally occurring element. A resonance has been observed for the Pm isotope (half-life 2-62 y) using sources of Nd prepared by an (n, y) reaction on NdzOa [6]. Nine compounds as absorbers all gave a 91-06-keV single resonance line at 4-2 K with no detectable chemical isomer shift. No further details are available. 

The heteronuclear mixed-valence complexes 16b,c were obtained from H2L 15, triethylamine, and iron(III) chloride in the presence of an excess of cobalt(II) chloride or copper(II) chloride. In neutral 16b,c iron is present only in the oxidation state 3 , as unambiguously confirmed by Mossbauer spectroscopy, which reveals only one quadruple doublet. Cyclic voltammetric investigation of the redox-active metal centers of neutral 16b shows a reversible three-potential one-electron transfer process. The half-wave potentials of -660 and -1310 mV correspond to the redox processes [(Fe )2Co"OLf ] [Fe Fe Co OLf ]" [(Fe")2Co"OLf ] , whereas... 

Iron-57 is the most important Mossbauer nuclide even though it has a natural abundance of only 2.2%. The half-life of its 14.41 keV excited state is 98.1ns and the half-life of its precursor source, cobalt-57, is 270 days. As a result, the resolution of iron-57 Mossbauer spectroscopy, 6.5 X 10 —the ratio of the linewidth to the 7-ray energy—is excellent. Because the typical iron-57 hyperfme parameters are of the order of a few millimeters per second and range up to many times the natural linewidth of 0.194mm s they are easily measured with excellent resolution. 

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