SYNOPSIS

#include <cerf.h>

double voigt ( double x, double sigma, double gamma );

DESCRIPTION

The function voigt returns Voigt's convolution

  voigt(x,sigma,gamma) = integral G(t,sigma) L(x-t,gamma) dt

of a Gaussian

  G(x,sigma) = 1/sqrt(2*pi)/|sigma| * exp(-x^2/2/sigma^2)

and a Lorentzian

  L(x,gamma) = |gamma| / pi / ( x^2 + gamma^2 ),

with the integral extending from -infinity to +infinity.

If sigma=0, L(x,gamma) is returned. Conversely, if gamma=0, G(x,sigma) is returned.

If sigma=gamma=0, the return value is Inf for x=0, and 0 for all other x. It is advisable to test input arguments to exclude this irregular case.

RESOURCES

Project web site: http://apps.jcns.fz-juelich.de/libcerf

REFERENCES

Formula (7.4.13) in Abramowitz & Stegun (1964) relates Voigt's convolution integral to Faddeeva's function w_of_z, upon which this implementation is based:

   voigt(x,sigma,gamma) = Re[w(z)] / sqrt(2*pi) / |sigma|

with

   z = (x+i*|gamma|) / sqrt(2) / |sigma|.

AUTHORS

Joachim Wuttke <[email protected]>, Forschungszentrum Juelich,
  based on the w_of_z implementation by Steven G. Johnson [http://math.mit.edu/~stevenj], Massachusetts Institute of Technology.

COPYING

Copyright (c) 2013 Forschungszentrum Juelich GmbH

Software: MIT License.

This documentation: Creative Commons Attribution Share Alike.