The Kramers Kronig Transformation is used for obtaining absorbance and
refractive index information from reflectance data. Measuring a reflectance
spectrum from an optically dense material will yield a complex spectrum
with two components - the absorbance spectrum and the refractive index
spectrum. The Kramers Kronig transformation will extract these components
from the complex reflectance spectrum.
The Kramers Kronig transformation assumes reflectance angles near zero.
The output of the transformation strongly depends on the measurement quality,
artefacts in the low wavelength region need to be eliminated properly
or the transformation will yield inadequate results.
Because of the material constants - which are required for the calculation
but are unknown to the software - the spectrum has to be extrapolated
to zero wavelengths. Consequently it is necessary, depending on the available
equipment and IR-Spectrometer, to measure as close as possible to the
lowest available wavelength. This will decrease the influence of the extrapolation
on the Kramers Kronig transformation.
The dialog for the Kramers Kronig transformation looks like this:
The following options are available for the
Specifies the calculation method for the Kramers Kronig transformation:
Uses Fast-Fourier-Transformation for the calculation
Uses MacLaurins formula for the calculation
Specifies the material constant. The default setting is 25 which represents
a conductive material. The material constant has influence on the algorithm
used for extrapolation and may be used to adapt the calculation to the
Controls the automatic normalization of the resulting spectra:
Theresulting spectra will
be automatically normalized between 0 and 2.
The resulting spectra will not be normalized.
Create Refractive Index Spectrum
Controls the type of result spectrum for the transformation:
A refractive index spectrum will be created and displayed as result.
An absorbance spectrum will be created and displayed as result.