1D NMR line shape for the U model, no temperature/field dependence. This is binary 1:1 binding model.
'Rtotal', 'LRratio', 'K_A', 'k_2_A', 'w0_1', 'w0_2', 'FWHH_1', 'FWHH_2', 'ScaleFactor'
ScaleFactor is, typically, a common multiplier for all slices originating from the same spectrum.