## Info

I+

90y -

1 I+ 2 I

- 21-

-Iz

I+

90-x -

1 I+ 2 I

+ 21-

-iIz

I+

90-y -

1 I+ 2 I

- 21-

+ Iz

(these can all be calculated using the definitions I+ = Ix + i Iy, I- = Ix - i Iy and the relations Ix = 1/21+ + 1/21-, i Iy = 1/21+ - 1/21-) Note that as we increment the phase of the pulse by 90° (x, y, -x, -y), the phase factor multiplying the resulting I+ component (Ap = 0, no change in coherence order from the original I+ spin state) does not change, whereas the phase of the I- component (Ap = -2) is shifted by 180° each time. The Iz (sometimes written as Io) component (Ap = -1) is shifted in phase by 90° each time if we use the complex plane (x' = real, y' = imaginary) to represent the phase (i, -1, -i, 1 correspond to the /, -x', -y and x axes, respectively, in the rotating frame). In general, the effect of a change in pulse phase A\$p on the phase of the resulting coherence depends on the change in coherence order Ap caused by the pulse

In the above example, A\$p = 90° and A\$c = 0°, 180°, and 90° for Ap = 0, -2, and -1, respectively.