  Measuring the Hamiltonian of dipolar coupled spin systems is usually a
difficult task due to the high complexity of their spectra. Currently,
molecules with unknown geometrical structure and low symmetry are extremely
tedious or impossible to analyze by sheer spectral fitting. We present a novel
method that addresses the problem of spectral analysis, and report experimental
results of extracting, by spectral fitting, the parameters of an oriented
6-spin system with very low symmetry in structure, without using a priori
knowledge or assumptions on the molecular geometry or order parameters. The
advantages of our method are achieved with the use of a new spectral analysis
algorithm - NAFONS (Non-Assigned Frequency Optimization of NMR Spectra), and by
the use of simplified spectra obtained by transition selective pulses. This new
method goes beyond the limit of spectral analysis for dipolar coupled spin
systems and is helpful for related fields, such as quantum computation and
molecular structure analysis.
