Generally phasing is set up to be have 0 0 phase
corrections for the indirect
dimension
Alternatively, it can be 90 -180, if the sampling
delay corresponds to exactly half the dwell
time.
In most experiments the pulseprogramme will make this
so.
However, for some of the Bruker canned experiments,
particularly the 15N edited NOESY and TOCSY
spectra this is not the case.
You can calculate the expected
phases.
For the indirect 1H dimension in the NOESY
experiment the sequence for evolution in t1 is:
90(1H)---d0---180(15N)---d0----90(1H)
the
effective sampling delay tau is therefore given by
4*90(1H)/pi
+ 2*d0 + 180(15N)
in our syntax
(brukers)
4*p1/pi + 2*d0 + p22
The
linear phase is then given by (for states-tppi):
phase(1) =
(tau/in0) *180
As an example: for my NOESY experiment p1
= 16.67; p22 = 70; d0 = 3; in0 = 79.34
so tau = (4*16.67/pi) +
6 + 70
thus tau = 97.22
so the linear phase correction is
97.22/79.34 * 180
= 220.56
the zero order phase
correction is half this: = -110.28
so input phc0 =
-110.28
phc1 = 220.56
NOTE: you do not need to scale the
first point
CAVEAT: the bruker spectrometer sometimes applies
a phase correction (usually 90), it should not affect
this unless you are processing in the echo anti-echo
mode.
When I find the inclination I will change the setup so the
phase correction is 0 0, but in the meantime this works.
For
more info see:
Bax et al.. JMR 91, 174-178 (1991)
or me.