If there are two peaks in the spectrum, we can work out the effect of a pulse sequence by treating the two lines separately. There is a separate magnetization vector for each line.
Suppose that a spectrum has two lines, A and B. Suppose also that line A is on resonance with the transmitter and that the offset of line B is 100 Hz.
Starting from equilibrium, we apply the following pulse sequence:
90° (x) - τ - 90°(x)
Using the vector model, work out what happens to the magnetization from line A.
Assuming that the delay r is set to 5 ms (1 ms = 10-3 s), work out what happens to the magnetization vector from line B.
Suppose now that we move the transmitter so that it is exactly between the two lines. The offset of line A is now +50 Hz and of line B is -50 Hz.
Starting from equilibrium, we apply the following pulse sequence:
90°(x) - τ
Assuming that the delay τ is set to 5 ms, work out what happens to the two magnetization vectors.