Constant-time period with J evolution

There is only evolution of J_XY coupling in systems where X and Y are heteronulei (2*d4=1/4J_XY).

   

Evolution of X chemical shift: (t₁/2)+d4+(d5-d4)-(d5-t₁/2)=t₁
Evolution of J_IX coupling constant: (t₁/2)-d4-(d5-d4)+(d5-t₁/2)=0
Evolution of J_XX' coupling constant: (t₁/2)+d4+(d5-d4)+(d5-t₁/2)=2*d5
Evolution of J_XY coupling constant: (t₁/2)+d4-(d5-d4)+(d5-t₁/2)=2*d4

Example 1: Constant-time  ¹³CA period and evolution of J_CACO in a 3D CT-HCA(CO)N experiment with I=HA, X=CA and Y=CO.

A particular case is when d4=d5.

Easy implementation on AVANCE spectrometers.