pseumod
Introduced in 1.0
Synopsis

Compute pseudo-modulated EPR spectrum.

yMod = pseumod(x,y,Ampl)
yMod = pseumod(x,y,Ampl,Harmonic)
Description

pseumod computes the effect of modulating the field on the EPR spectrum. Modulation of the external static field is standard in CW EPR spectroscopy. Because of modulation, the recorded signal is approximately the first derivative of the spectral shape and not the absorption spectrum itself. Given an absorption spectrum y over a field range x (in mT), pseumod returns the modulated spectrum in yMod.

The parameter Ampl specifies the peak-to-peak modulation amplitude in mT, as it is usually specified when measuring EPR spectra. Harmonic allows for the selection of the detection harmonic of the modulated spectrum. 1 gives the first derivative and is the default value, higher values give higher derivatives.

The routine returns a pseudo-modulated spectrum in the sense that it only takes into account the effect of the modulation amplitude, completely neglecting possible effects of the modulation frequency on the spectrum, like sidebands for narrow lines.

Examples

Suppose spec is an absorption spectrum over fieldrange. Then the effect of first-harmonic detection with a field modulation amplitude of 50 Gauss (peak-to-peak) is

fieldrange = linspace(340,360,500);
spec = gaussian(fieldrange,350,1);
ModAmplitude = 5; % units are mT !
specMod = pseumod(fieldrange,spec,ModAmplitude);
plot(fieldrange,specMod);
xlabel('magnetic field [mT]');

The modulation amplitude is much bigger than the line width, and the effect of overmodulation is clearly visible.

Algorithm

The function implements a procedure described in

See also

garlic, gaussian, lorentzian, lshape, pepper