Relayed-COSY The considerations about transfer functions become more important in experiments with fixed delay e.g., for coupling evolution. The simplest homonuclear experiment here is the Relayed-COSY, with the following pulse sequence t It allows to correlate the chemical shifts of spins that are connected by a common coupling partner, as in the linear coupling network I1-12-I3, with the coupling constants J12 and J After the tI evolution period and the second 90 pulse we get(cf. COSY) I1z cos(Q2jt1) cos(TJ12tD) 211,2x cos(Q2jt1) sin(TJ12t1) Ily sin(Q21t1)cos(IJ12tD) +211zI2x sin(Q21t1)sin(TJi2t1) During the period A, chemical shift evolution is refocussed(180% pulse in the center!), but J12 coupling evolution continues I1zcos(Ω21t1)cos(πJt1) (no coupling evolution, Iz D) 211 2x cos(@ t1 sin(IJ12t1) (no coupling evolution, MQC!) ly sin(S2 t1) cos(IJ12t1) cos(TJ124) 2I1xI2zsin(2t1)cos(πJ1t1)sin(J12△) (evolution of antiphase) 211212x sin( Q2jt1) sin(TJ12t1) CoS(TJ124) L2y sin(21t1)sn(πJt)sin(πJ2A) (refocusing to in-phase)52 Relayed-COSY The considerations about transfer functions become more important in experiments with fixed delay, e.g., for coupling evolution. The simplest homonuclear experiment here is the Relayed-COSY, with the following pulse sequence: It allows to correlate the chemical shifts of spins that are connected by a common coupling partner, as in the linear coupling network I1 — I2 — I3 , with the coupling constants J12 and J23 . After the t1 evolution period and the second 90° pulse we get (cf. COSY): ¾® - I1z cos(W1 t1 ) cos(pJ12t1 ) + 2I1yI2x cos(W1 t1 ) sin(pJ12t1 ) + I1y sin(W1 t1 ) cos(pJ12t1 ) + 2I1zI2x sin(W1 t1 ) sin(pJ12t1 ) During the period D, chemical shift evolution is refocussed (180° pulse in the center!), but J12 coupling evolution continues: J12 ¾® - I1z cos(W1 t1 ) cos(pJ12t1 ) (no coupling evolution, Iz !) + 2I1yI2x cos(W1 t1 ) sin(pJ12t1 ) (no coupling evolution, MQC!) + I1y sin(W1 t1 ) cos(pJ12t1 ) cos(pJ12D) - 2I1xI2z sin(W1 t1 ) cos(pJ12t1 ) sin(pJ12D) (evolution of antiphase) + 2I1zI2x sin(W1 t1 ) sin(pJ12t1 ) cos(pJ12D) + I2y sin(W1 t1 ) sin(pJ12t1 ) sin(pJ12D) (refocusing to in-phase)