Mossbauer synchrotron stroboscopy
[Mossbauer radioactive source]
After this decission for a theory of a Mossbauer transmission experiment Effi may ask on 4 levels for theories (or even trees of theories): Level 0 (global theory), level 1 (device), 2 (module),and 3 (component).
The geometry of the Mossbauer transmission experiment belongs to the global theory, which handels the results of the devices. For this example EFFI asks for:
cosine smearing & aperture effect
misalignment: point source-absorber-detector
This example has no theories on level 1 and 2. The source device is restricted (by the programmer - not by EFFI) to one module/layer. Each layer is oriented in space and exposed to an external field. Such parameters are offered and if they are not taken EFFI put them to zero. At the component level for each site a theory tree is presented.
[scalar refraction index (static,sad)]
scalar refraction index (dynamic,sad-interpol.)
scalar refraction index (dynamic,sad)
2x2 refraction index (static,sad)
2x2 refraction index (static,f_anisotrop,sad).
In the case of a scalar refraction index of the sample (a powder sample without polarisation) 6 simple theories are offered:.
[singlet: width, position and intensity]
doublet: width, position and intensity
sextet : width, position and intensity
(this choice corresponds to a single line source or absorber).
Each of these 'theories' could have an own decission tree (not the case here). Effi allows up to 8 recursive branches. It should also be mentioned that the decission for each device, module, component can be a different one. The tree structure guarantees that all theories arriving at a special branch have available the full structure of this branch down to all its levels.
Simultaneous fit of several data sets is achieved by correlation of parameters of theories defined somewhere in the decission tree. EFFI provides a group of commands to correlate parameters with no restriction to the meaning/type of parameters. Principally the user can produce a lot of nonsense. The correlation is obtained by transformation matrices which were introduced by L. Pócs in the late sixties. The use and handling is described in the help files of EFFI.Installation
The program runs under LINUX and is not portable to WINDOWS. Till version 5.n.n the
distribution of EFFI follows an unusual procedure
which leaves to the user to compile the source code of the
theories. The theories are written mainly in Fortran and the
plot routines for X-Window in C-language. The EFFI part was hidden by
the binary code and collected in an archive (static library named areffi.a).
The last version which can be translated with the GNU compiler g77 is
effi_3.3.0. The fortran files have the extension .f. The modern GNU
compiler gfortran translates the syntax of fortran90 and higher which
have the extension .f90.
There are several README files, the one for detailed instructions for the compilation procedure and linking are found in README.1 which follows the syntax of the command man: man ./README.1 (see README). There is also an install script which does the job.
Since version 6.0.0 the complete source code is compiled by the install script which in turn calls the script compile for areffi.a.
This procedure should give the user a closer contact to the theories (something may be changed in order to look for the effect or printouts are put in). The use of the debugger makes visible what theories do in different steps. This way the routines may be improved, such that there is a chance for the whole program to survive.
After translation of the program several examples can be inspected. They are found in subdirectories of effi/project. effi/project/Mossbauer_source containes some examples of Mossbauer measurements. The directories Au197/, Eu151/, Eu153/, Ni61/, Gd155/, Gd156/, Sb121/, hsls_tr/, calibration/, mtz/, collins/, mohrsalt/, relaxation/, spinham/ contain README files and measurements (partly taken from the literature) simultaneously fitted, which demonstrate features of effi. A simultaneous fit of 19 spectra of different orientations of a single crystal can be found in the almandine and mohrsalt directories. The spectra of almandine have been fitted with 2 inequivalent sites in a crystal of cubic symmetry split by quadrupole interaction. The 2x19 second rank tensors are correlated by the transformation matrices, a good example to see how the transformation matrices work.