SETTING UP YOUR EXPERIMENT
	Acquire data (continued).
	However, recall that most of the nuclei are precessing at rates slightly faster than the Larmor frequency. In other words, their motion will combine motion in the x-y plane with a return to equilibrium. This gives rise to an oscillating signal, as shown below (click on the image to start; roll your mouse over it to replay). When the magnetization lies along the the +x axis, the signal is both positive and at a maximum value, as shown by the red arrow. As it moves toward the +y axis (90o), the projection (green vector) decreases in intensity, but is still positive. The signal goes through zero at the +y axis, then increases (but with negative sign), until it reaches a minimum at 180o. From this point, it increases steadily, passing through zero again at 270o.
	After the magnetization returns to the starting point, on the +x axis, the whole cycle starts over again. The resulting signal, you might recognize, is described by the cosine function:
	If you combine this oscillation with the T1-induced exponential decay, the result is a damped cosine wave:
	The curve above describes the theoretical behavior of an off-resonance signal, if it were observed for a time equal to the experimental acquisition time plus the pulse delay (assuming the delay is 5-10X T1). However, we have seen that a real NMR FID decays much faster, during the acquisition time alone. Why does the experimental signal decay so much more rapidly than the theoretical? Click below to find out!