The U-model-LRcorrection model written to fit a doublet (a resolved or unresolved coupling).
A required condition is that J-coupling constant is NOT dependent on exchange process. This is the case with most non-covalent binding interactions. The example of J-coupling altered by exchange would be GMP+P=GDP reaction. If a coupling is different in two exchanging states---the formalism used for simulation of line shapes BECOMES INVALID.
'Rtotal', 'LRratio', 'K_A', 'k_2_A', 'w0_1', 'w0_2', 'FWHH_1', 'FWHH_2', 'ScaleFactor', 'LRcorrection', 'Jconst'