Thanks for clearing that up.

Are there any plans to introduce more interactions/physical properties
in future versions of SIMPSON? Perhaps the inclusion of T1/T2 or
chemical shift distribution (as in the case of my D20 peak)?

Stevie

--- In simpson-simmol@yahoogroups.com, Thomas Vosegaard <tv@...> wrote:
>
> Hi Stevie
>
> Instead of using computer power on optimizing parameters for the D2O
> peak, I would either only fit the region of the spectrum not
> influenced by this peak. You can do this by specifying optional
> regions to the frms command (syntax would be something like frms $f $g
> {0 10000} {12000 14000}).
>
> If you have important features under the D2O peak so the above idea
> doesn't work, then I would suggest you only optimize the linewidth of
> the D2O peak (if you cannot estimate a fixed value for it) and then
> handle the relative scaling of the two spectra using the approach I
> sketched in a mail to the simpson-simmol user group in June 2002
> (Subject: Re: [simpson-simmol] overlapping lineshapes using simpson).
> This procedure avoids using minuit parameters to fit it - so it's less
> prone to falling into wrong minima.
>
> The maxdt parameter defines the maximum time over which the
> Hamiltonian is considered constant in the case of MAS. This matters
> for the speed of the calculation if you have pulses. With maxdt 1 you
> will split the pulse into 1us steps and diagonalize for each step.
>
> When you have a pulse sequence which only consists of "delay 9999", it
> is probably using the method gcompute and a start operator of I1x. So
> it starts with x coherence on the nucleus you want to detect, so no
> need for pulses. gcompute is a fast method to propagate when you have
> a rotor-synchronized pulse sequence - and a free-induction decay
> sampled with a spectral width of n*spin_rate is rotor synchronized. In
> this case the pulse sequence shouldn't contain any information on the
> sampling - this is specified by the spectral width and spin rate (and
> gamma_angles, which needs to fulfill the requirement sw =
> spin_rate*gamma_angles). The pulse sequence needs only contain the
> information on the first rotor period.
>
> Thomas
>
>
>
>
> On Sep 9, 2008, at 22:43 , Stephen Greenwald wrote:
>
> > Hi guys,
> >
> > I'm a relatively new SIMPSON user. I've managed to figure quite a bit
> > out on my own, with much struggling, but there is something I cannot
> > seem to tackle. what is the best way to handle broadening of peaks
> > caused by something other than the four spinsys interactions?
> >
> > For example, I have fit a static powder pattern of fully deuterated
> > oxalic acid-dihydrate. The spectrum is a clean pake doublet (the
> > oxalic acid deuterons) with a broad D2O peak in the middle. I could
> > not, for the life of me, figure out how to simulate the D2O peak and
> > so ended up zeroing out that portion of the spectrum and fitting only
> > the pake portion.
> >
> > I tried to use faddpeak, but the program would not compile with
> > variables inside the double curly bracket faddpeak takes asw an
> > argument (ie "faddpeaks $f 1e-5 {{0 $mn(int) $mn(lb) 1}}" was not
> > proper syntax).
> >
> > So what is the bet way to handle broadening? "faddpeak" might do the
> > job in some instances but it would fail for any spectra with
> > interacting spins. What if I want to generate a spectrum of two peaks
> > of different broadness that also had jcoupling or dipole interactions?
> >
> > One other question: I have seen a few examples whose pulseseq section
> > contains only "maxdt 1" and "delay 9999". What does this signify?
> > How is a spectrum generated without any pulses?
> >
> > Thanks
> > Stevie
> >
> >
> >
>