 Examples of inhomogeneous effects include a magnetic field gradient and a distribution of chemical shifts.If the inversion pulse is applied after a period "t" of dephasing, the inhomogeneous evolution will rephase to form an "echo" at time "2t".In simple cases, the intensity of the echo relative to the initial signal is given by "e–2t/T2" where T2 is the time constant for spin-spin relaxation.