Consider the pulse sequence shown below.

Starting with equilibrium magnetization on spin one, 1z, show that the sequence generates a mixture of double- and zero-quantum coherence. Find the value of r which gives the maximum amount of multiple-quantum coherence. [Can you spot the spin echo? If so, the calculation is much simpler.)
Show that if we start with equilibrium magnetization on both spins one and two, i.e. lz + 2, the sequence generates only double-quantum coherence.