Figure 5: Echo detection of T₁.

The echo signal is shown (as points) as a function of the arrival time of the echo sequence relative to the fixed preparation pulse (τ₁₂). The echo intensity was normalized to its value when the preparation pulse was blocked (A₁=0). At large positive or negative delay the echo is independent of the preparation pulse. At intermediate times the partial relaxation means that the echoes from the excited state and ground state oscillators compete. The solid lines show the theory averaged over the beam profile. NB: for small negative delay −100 ps<τ₁₂<0, the preparation pulse arrives in the middle of the echo read-out sequence and the response does not follow a simple intuitive picture. The different colours are for different preparation pulse areas A₁.