Free Evolution

During free evolution transverse magnetisation will evolve due to J-coupling and chemical shift. No pulses are applied during the free evolution period.

So for a homonuclear coupled two spin system if we begin the free evolution period with transverse magnetisation (I_1X) then after the free evolution period we would have in phase transverse magnetisation for I₁ modulated by terms in chemical shift for I₁ and J-coupling between I₁ and I₂ as along with antiphase magnetisation for I₁ with respect to I₂ again modulated by terms in chemical shift for I₁ and j-coupling between I₁ and I₂.