Some notes and tips on phasing:

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Interactive Phasing

NMRDraw will automatically reconstruct imaginary data as needed,

so it is always possible to interactively rephase any 1D spectral

vector being viewed, from any dimension:

1. Use "1D/1D Vertical", "1D/Z-Axis" etc to activate 1D viewing mode.

2. Use the mouse to select a 1D vector of interest.

3. Click the "Phase" button in the command "On" to activate

interactive phasing.

4. Use the "P0" and "P1" sliders or text entries to adjust the phase as

needed.

Note that in any 1D viewing mode, when the mouse pointer is outside

the 1D viewing area in the bottom or right border, dragging with

the rightmost mouse button will change the position of the phase pivot

point. The position of the pivot will be indicated on the 1D display

by arrows. The pivot shows the position in the spectrum whose phase

will stay fixed as P1 is adjusted.

It is also possible to phase correct two or more vectors

simultaneously. To keep a given vector on the screen,

use the "1D/Append 1D" command. Then, continue to select

other vectors to view with the mouse as usual. Any phase

adjustments selected as above will be applied to all 1D

vectors at once.

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Big FD's phase correction hints:

0. When possible, take great care to acquire the data so that the

indirect phases are known in advance.

1. Always use trial processing of the first XY and XZ planes

of a 3D to confirm overall phase corrections etc.

2. Try at first to process the direct dimension without any

first order phase.

3. If you are not sure of the phase in an indirect dimension,

try the "standard" values -90,180 and -180,360 before

resorting to interactive phasing. If these don't work,

try keeping the P1 at 180 or 360, and then adjusting only

P0 interactively.

4. If the "standard" values don't work, move the pivot to

the exact center of the spectrum, set P0 to 0.0, and try phasing

the spectrum with just the P1 sliders. Having the pivot at the

center will force the phases to obey: P1 = -2*P0. The center

of the spectrum is point N/2 + 1 (e.g. point 65 of 128).

5. If the "constrained" phases don't work, try completely interactive

P0 and P1 phasing by the usual methods:

i. Select one or more spectral vectors which have

peaks over the full range of the spectrum.

ii. Move the pivot to point to a "good" peak.

iii. Change P0 until that peak is phased.

iv. Change P1 until the overall spectrum is phased.

v. Repeat (iii) and (iv) for minor adjustments if needed.

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Using NMRDraw Phase Corrections in a Script

The phase corrections reported by NMRDraw can be used directly

in an NMRPipe processing scheme, regardless of the pivot position

used to phase the spectrum. You can usually simply add the P0 and

P1 values reported by NMRDraw to the -p0 and -p1 parameters in the

original processing script. The exception to this is if you have

interactively re-phased an extracted (EXT) dimension with a first

order correction. In this case, you should be sure that the phase

correction is applied after the EXT extract in the processing scheme:

| nmrPipe -fn EXT -left -sw \

| nmrPipe -fn PS -p0 43 -p1 180 -di \

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Initial Delay and Phase Correction

If a dimension is acquired with:

No delay:

1. No first-order phase correction.

2. Scale first FID point by 0.5 (window -c 0.5)

Half point delay:

1. 180 first-order phase correction (Usually -90,180)

2. Don't scale first FID point (window -c 1.0)

One point delay:

1. 360 first-order phase correction (Usually -180,360)

2. Don't scale first FID point (window -c 1.0)

3. Apply zero-order baseline correction to spectrum

(POLY -auto -ord 0)