(* Oliver Schedletzky, Burkhard Luy and Steffen J. Glaser, Analytical Polarization and Coherence Transfer Functions for Three Coupled Spins 1/2 under Planar Mixing Conditions Journal of Magnetic Resonance 130, 27-32 (1998). A Hamiltonian of the form H=2 pi J (I1xI2x + I1yI2y) is assumed (expanded to 3 spins, of course). The effective planar couplings between spins 1 and 2 is called j12 etc.. The coupling constants have to be defined right after the Clear command below. The variable transfer12 will give the polarization transfer function for I1z -> I2z under the above mentioned Hamiltonian. Correspondingly transfer13 or transfer11 corresponds to I1z -> I3z and I1z -> I1z, respectively. Transfer functions to zero quantum operators should be clear from the name given (e.g. transfer11y2z corresponds to the coherence transfer function I1z -> I1yI2z). Please cite the above mentioned reference whenever you use this program for scientific work. SPECIAL CASE J12=J13=J23 *) Clear[j12,j13,j23,x1,x2,x3,y1,y2,y3,z1,z2,z3,v1,v2,v3,w1,w2,w3, n1,n2,n3,c1,c3,lamb1,lamb2,lamb3,delta12,delta13,delta23, h, phi,s,p] j12=10 a12=4/9 b12=4/9 b0=5/9 delta12=lamb1-lamb2 lamb1=2 Pi j12 lamb2=-Pi j12 transfer12= N[(a12*Sin[delta12/2 t]^2)] transfer11= N[(b0+b12*Cos[delta12 t])] Plot[transfer12, {t,0,1}] Plot[transfer11, {t,0,1}]