Subject: Fourier transformation of autocorrelation functions

From: Hannes Loeffler <[email-masked]>
Date: Thu, 20 Jun 2002 18:31:07 +0200

Hi,

I have some practical question regarding Fourier transformations of
autocorrelation functions:

1) Is there some way to determine the "correlation length" (time until
   autocorrelation function is "sufficiently" zero) a priori?

2) The long time behavior is usually statistically less well determined.  At
   which time may I cut/ignore the function values?  Any rules of thumb?

3) If only the short time correlation function is used for Fourier
   transformation do I need to smooth the correlation function to let it go
   smoothly to zero at the cutoff limit?  If yes, which window function should
   choose?

4) When should I use filtering (e.g. Golay-Skalitzky) of the Fourier transform?
   May I use a filter if the autocorrelation function has already been smoothed
   or would the final result be too artificial?

I would be grateful for any comments,
Hannes.

-- 
Hannes Loeffler | tel: +43-(0)512-507-5166 | fax: +43-(0)512-507-2714
http://www-c724.uibk.ac.at/staff/loeffler/ | mailto:[email-masked]
Institute for General, Inorganic and Theoretical Chemistry
University of Innsbruck, Austria