Pulse delay is the distance between the first and the second
pulse of the spin echo pulse sequence in microseconds. In the
intermediate motion regime the pulse spacing influences the line shape considerably.
For spin 1/2 systems Weblab takes the Hahn echo π/2x-πy, for spin=1 the quadruploar echo sequence π/2x-π/2y.
Weblab always assumes ideal pulses of infinite strength. In reality one has to use proper phase cycling to compensate for pulse imperfections.