User Tools

Site Tools


documentation:fittey
math plugin disabled: PHP's gd library is missing or unable to create PNG images

Documentation for FitTEY

The program FitTEY is a toolbox to fit the total electron yield (TEY) or calculated spectra to off-resonant tables (optical constants delta, beta or scattering factors f1, f2) and to do Kramers-Kronig calculations in one step. Furthermore it can create new optical constants for compounds.

Fit

Usage: FitTEY is a console application.

FitTEY.exe fit mode file1 file2 element model cutmin cutmax fitmin1 fitmax1 fitmin2 fitmax2 a b c shift
fit [string]

This is the command and should be exactly this string

mode [string]

“db” or “ff” or “cF” dependent what you want to fit

  • mode=“ff”: atomic conductivity to atomic scattering factor
  • mode=“F” : atomic conductivity tensor to atomic scattering tensor
  • mode=“db”: conductivity to refractive index
file1 [string]

file containing the measured or calculated data dependent on the mode variable.

  • mode=“ff”: filename with data to merge with columns [energy 0 conductivity]
  • mode=“F” : filename with columns [energy conductivity tensor(18 entries)]
  • mode=“db”: filename with data to merge with columns [energy 0 conductivity]

Look in the file formats section of this documentation for more information

file2 [string]

File containing the off-resonant data dependent on the mode variable

  • mode=“ff”: filename with columns [energy f1 f2]
  • mode=“db”: filename with columns [energy delta beta]
  • mode=“F” : filename with columns [energy f1 f2]

Look in the file formats section of this documentation for more information

element [string]

Chemical element or Chemical formula dependent on the mode variable

  • mode=“ff”: chemical element e.g. Ni
  • mode=“F” : chemical element e.g. Ni
  • mode=“db”: chemical formula e.g. LaNiO3
model [string]

the model describes the different fitting models

model mode formula fit parameters fixed parameters Comments
A db beta(E) = (t(E) / E) * a + b + c * E a b c
B db beta(E) = (t(E) / E * a + b + c * E a b c
C db beta(E) = (t(E) / E) * a + b + c * E a b c
N db beta(E) = (t(E) / E) * a + b + c * E a b c
D db beta(E) = (t(E)*a*sin( c*pi/180. ) / (1. - t*a) / b) / ((5.067769e-4 * E * 2.) a b c
E db beta(E) = (t(E)*a*sin( c*pi/180. ) / (1. - t*a) / b) / ((5.067769e-4 * E * 2.) a b c
F db beta(E) = (t(E) / E) * (a + c * E) + b a b c
A ff f2(E) = (t(E) * E) * a + b + c * E a b c
B ff f2(E) = (t(E) * E) * a + b + c * E a b c
C ff f2(E) = (t(E) * E) * a + b + c * E a b c
F ff f2(E) = (t(E) * E) * (a + c * E) + b a b c
G db/ff beta(E)/ff(E) = t(E) * a + b + c * E a b c not officially supported
H db/ff beta(E)/ff(E) = t(E) * a + b + c * E a b c not officially supported
I db/ff beta(E)/ff(E) = t(E) * a + b + c * E a b c not officially supported
J db/ff beta(E)/ff(E) = t(E) * a + b + c * E a b c not officially supported
K ff ff(E) = t(E)*E*E * a + b + c * E a b c not officially supported

In all models the parameters a acts like a scaling factor for the TEY data. The variables t is the TEY signal and the parameter e is the energy in eV.

Model D and E take the self-absorption into account. (Reiko Nakajima “Electron-yield saturation effects in L-edge x-ray magnetic circular dichroism spectra of Fe, Co and Ni” PRB Volume 59, Number 9 (1999) ) by the formulas

with

Parameter a is a scaling factor for the TEY signal. Parameter b is the escape length of the electrons in Angstrom. Paramter c corresponds to the Variable and is the angle (in degrees) of the incoming beam (perpendicular incoming ray is c=90). Variable k0 is the wavenumber of the incoming ray.

cutmin [number], cutmax [number]

Energy range in eV for the measurement which should be merged with the off-resonance data.

fitmin1 [number], fitmax1 [number]

Energy range used for fit before resonance

fitmin2 [number], fitmax2 [number]

Energy range used for fit after resonance

a [number]

Initial value for fit parameter a. Depends on the used model. In most cases a good initial value is a = 1.

b [number]

Initial value for fit parameter b Depends on the used model. Good initial starting could be b = 0.

c [number]

Initial value for fit parameter c. Depends on the used model. Good initial starting could be c = 0.

shift [number]

Energy shift of the measurement. If unsure set it to zero.

output merged.??

The output of the program is a file called merged.db or merged.ff with the fitted and merged TEY-data. It is dependent on the mode variable

  • mode=“ff”: filename with columns [energy f1 f2]
  • mode=“db”: filename with columns [energy delta beta]
  • mode=“F” : filename with columns [energy conductivity tensor(18 entries)]

Create

To create the off resonant values of the refractive index for a compound you can use following command

FitTEY.exe create chemical_formula density shift
density [number]

density of the compound in units of g/cm^3

shift [number]

Energy shift of the off resonant values. If unsure set it to zero.

Convert

This command converts the fitted refractive index to atomic scattering factors

FitTEY.exe convert file1 chemical_formula density element cutmin cutmax shift
file1

fitted .db file with resonances

element

Element to extract from the file

cutmin, cutmax

Lowest and highest energy values for the resonance you want to merge.

shift [number]

Energy shift of the off resonant values. If unsure set it to zero.

documentation/fittey.txt · Last modified: 2013/11/28 11:45 by macke