Looks to me like it's just a logic problem.

Your code skips the if {} when t1=1, so your first propogator 4 is null,
but gets time indexed for the beginning of the rotor cycle (equivalent to
having used "reset 0" before your if {} statment. Your next t1 incr
executes prop 1 which takes 2 x 5.5 us, but then tries to use prop 4 which
was calculated to start at the beginning of a rotor period. Hence the
error.

Cheers
john


> Hello Everyone,
>
> I am trying to simulate 1H-15N dipolar lineshape using R18(1,7). I have
> attached my simpson code at the end. I get the following error message
> when I run it.
>
> ---------------------------------------------------------------------
> error: a propagator was calculated at time 0usec
> relative to the start of the rotor period but reused at time 11.1usec.
> ---------------------------------------------------------------------
>
> The rotor period is 100 us (10 kHz spinning speed) and the dwell time is
> 11.1 us (two 180 pulses at 90 kHz rf field strength)
> Does this error message have anything to do with dw not being
> synchronized with the rotor period?
>
> Can anyone help?
>
> Thanks in advance,
>
> Sivakumar
>
>
> Here is my code (I used Example 6, SLF experiment on simpson paper as a
> template to code this one)
>
> ----------------------------------------------------------------------
> spinsys {
> channels 1H 15N
> nuclei 1H 15N
> dipole 1 2 11800 0 0 0
> shift 1 0p -1.0p 0.0 0 0 0
> }
>
> par {
> start_operator I2x
> detect_operator I2p
> spin_rate 10000
> gamma_angles 36
> crystal_file rep320
> np 32
> verbose 1101
> proton_frequency 599.781541e6
> variable rf 90000
> variable tau 800
> sw 90090.090
> }
>
>
> proc pulseq {} {
> global par
>
> maxdt 2.5
>
> set t180 [expr 0.0555e6/$par(spin_rate)]
> set tsw [expr 0.111e6/$par(spin_rate)]
> set rf $par(rf)
>
> pulse $t180 $rf 70 0 0
> pulse $t180 $rf -70 0 0
> store 1
>
> for {set t1 1} {$t1 < $par(np)} {incr t1} {
> reset
> if {$t1 > 1} {
> prop 4
> prop 1
> }
> store 4
> set tdec [expr $par(tau)-$tsw*($t1-1.0)]
> pulse $tdec $rf 0 0 0
> pulseid 2 0 0 250e3 0
> pulse $par(tau) $rf 0 0 0
> acq
> }
> }
>
>
> proc main {} {
> global par
>
> set f [fsimpson]
> fsave $f $par(name).fid
> }
>
> --------------------------------------------------------------------
>
>


--
John Gehman
Research Fellow
School of Chemistry
Bio21 Institute
University of Melbourne (Australia)