Subject: Re: [nmr_sparky] exponential decay
From: Stefano Ciurli
Date: Jun 2, 2010
Previous: 720 Next: 722
Hi Tom,
thanks a lot. I would know how to use eq. b with another fitting
program but I will try to implement it in the python script within
Sparky. However, my question was also a bit more general: I wanted to
know how the community of NMR people deals with this problem, as it
is not clear from the literature and I am dealing with this problem
for the first time.
I hope someone in the list could also respond.
Stefano
On Jun 2, 2010, at 9:29 PM, Tom Goddard wrote:
Hi Stefano,
A modification to the Sparky relax.py file (sparky/python/sparky/
relax.py) could add the parameter C to the fitting. I think I did
this once upon a time but I cant find any code for it. Youd
modify the a_exp_bx_function class in the relax.py code. Maybe an
hours work to figure out change and test if you are familiar with
Python.
Tom
Hello,
when fitting T1 or T2 relaxation data one could use two equations:
a: A*exp(-t/B)
b: A*exp(-t/B) + C
In the first case one assumes that the maximum tau used in the set
of experiments is sufficient to bring to zero the intensity of the
signal, while in the second case one assumes that there may be a
residual intensity. Following my logic, I would prefer the second
case, because the spectrum with the largest tau still has non-zero
signals. However, Sparky uses the first equation. Of course, the
relaxation rates that are calculated in the two cases can be very
different. What is the commen/preferred protocol?
Stefano
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