(* 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 |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=4.6 j13=10.5 a12=+r1/6 a13=+r2/6 a23=+(r1*r2)/18 b23=2*(r1*r2)/9 r1=(Sqrt[2] Cos[psi] - Sin[psi])^2 r2=(Cos[psi] + Sqrt[2] Sin[psi])^2 psi=ArcTan[(Sqrt[2] /4)* (j12+8*j13-3*Sqrt[j12^2+8*j13^2])/(j12-j13)] delta12=lamb1-lamb2 delta13=lamb1-lamb3 delta23=lamb2-lamb3 lamb1=-Pi j12 lamb2=Pi/2 * (j12-Sqrt[j12^2 + 8*j13^2]) lamb3=Pi/2 * (j12+Sqrt[j12^2 + 8*j13^2]) com1=a12(1-Cos[delta12 t]) com2=a13(1-Cos[delta13 t]) com3=a23(1-Cos[delta23 t]) transfer11= N[1-(a12(1-Cos[delta12 t]) +a13(1-Cos[delta13 t]) +a23(1-Cos[delta23 t]))] transfer33= N[1-(b23(1-Cos[delta23 t]))]