EWVoigt
EWVoigt as part of EWWIN 2012 or as a stand-alone DOS program is designed for
simulation/optimization of inhomogeneously broadened EPR spectra, which are very common in EPR
spectroscopy (e.g., anisotropy broadening, hyperfine interaction, inhomogeneities in the magnetic
field and others).
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One simple example of an inhomogeneous line is a Voigt function which is a convolution of a Lorentzian and Gaussian line. Lorentzian/Gaussian convolution integrals cannot be integrated in a closed form, therefore different approximation techniques were previously applied.
The main application of the package is least squares simulation of solution spectra in regime of fast motion. The program is very advantageous in studies of microviscosity using nitroxide spin label/probe technique, it drastically improves the accuracy in EPR oximetry measurements (including low frequency EPR oximetry with a significant phase distortion of the spectra) and nitroxide reduction studies.
EWVoigt offers:
- the most accurate way of computing Voigt functions using a precision Fast Convolution algorithm;
- SPEED; it computes the Voigt function in a matter of seconds;
- optimization of simulated parameters to fit experimental data which is accomplished by a modified Levenberg Marquart algorithm which usually converges in 4 7 iterations;
- estimates of parameter uncertainties;
- sequential mode of processing of similar data automatic fit to a sequence of up to 100 data files.
The current version is capable of:
- reading any sequential ASCII or EW data file of up to 2048 datapoints (no limit in EWWIN 2012 version);
- accounting for up to 3 different types of paramagnetic centers with a common envelope function (no limit in EWWIN 2012 version);
- accounting for any number of non equivalent nuclei with 1/2 spins and optimization of corresponding hyperfine structure;
- optimizing spectra in "first integral" or "first derivative" mode;
- optimizing a dispersion contribution to the experimental spectra;
- accounting for a "fixed" hyperfine pattern which can be entered as any function digitized in a sequential file.
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Sample applications:
- Fitting a single component of CTPO EPR spectrum and extracting parameters of the hyperfine structure.
- Fitting an entire fast motion nitroxide spectrum and extracting Lorentzian contributions to each of hyperfine lines, Gaussian contribution to the linewidth, and the hyperfine constants.
- A precision extraction of Lorentzian broadening in EPR in vivo oximetry experiments, where the lineshapes are commonly distorted by dispersion contributions.
- Fitting a sequence of TEMPO spectra taken at different temperatures and extracting the aqueous and membrane spectra.
Coming soon...
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