WWW-Messbauer.Last Reviews
   WWW-Messbauer ABOUT WHAT'S NEW LAST REVIEWS

  WWW-Messbauer >> Last Reviews


Next · Previous

MESSBAUER SPECTRA OF AXIAL TEXTURES


Axial texture gives asymmetric doublet spectra of 57Fe and 119Sn, excess of Iπ component (δIπ) could be evaluated for perfect axial textures in different geometries of Messbauer experiments. The δIπ dependency on asymmetry parameter η and on the orientation of EFG tensor principal axes in single particle relatively the axial texture axis can be presented as

δIπ = Iπ - 0.5 = 3 [8 (1+a2)]-1 * (1 - 3cos2 γ0 )]*
*[1/3 (a2 - 1) + 0.5 sin2 Θ0 (1 - a2 + 2 * 3-1/2 * a cos 2 Β0)],

where

a = η [31/2 (1 + (1 + η2/3 )1/2)] -1

γ0 is the angle between the gamma-rays and the normal to the sample plain (axial texture);
Θ0 is the angle between the EFG tensor main axis (z) and the preferential crystallographic direction n of nonisometric particles in the texture.
Β0 - the angle between x-axis and the line, which is common for the xy plain and the plane, perpendicular to the n direction.
The δIπ value depends on two factors. The first one depends just on geometry of Messbauer experiment (the angle γ0 ), the second - just on the sample properties: local field parameter η and features of axial texture used - Θ0 and Β0.







The two-doublets spectra of Fayalite (300K) could not be evaluated completely without simplifying assumptions - the left their components are too close. To distinguish these two doublets completely one can by using two textured samples: axial texture and texture-90. Left and right components of each doublet could be definitely characterized numerically without any simplifying assumptions.

This method permits one to distinguish partial doublets in poorly resolved, complex spectra of minerals and to evaluate them without simplifying assumptions.