(* Burkhard Luy and Steffen J. Glaser, Analytical Planar Mixing Transfer Functions for Two Coupled Spin-1 Nuclei Journal of Magnetic Resonance 153, 210-214 (2001). A Hamiltonian of the form H=2 pi J (I1xI2x + I1yI2y) is assumed. The coupling constant has to be defined right after this comment. have to be defined right after the Clear command below. trans11 will give the transfer function for I1z -> I1z and trans12 the transfer function I1z -> I2z. Please cite the above mentioned reference whenever you use this program for scientific work. *) j12 = 10 trans11= 1-(1/6)*(2*(1-Cos[2*Pi*Sqrt[2]*j12*tau]) + (1-Cos[4*Pi*j12*tau])) trans12= (1/6)*(2*(1-Cos[2*Pi*Sqrt[2]*j12*tau]) + (1-Cos[4*Pi*j12*tau])) t11=N[trans11] Plot[t11, {tau, 0, 1}] t12=N[trans12] Plot[t12, {tau, 0, 1}]