On the convergence of iterative computation in the LAOCOON 3 program

The reasons which sometimes cause failure of convergence in the iteration of NMR spectra by LAOCOON 3 are discussed. The problem can be avoided by retaining the sequence of the eigenfunctions throughout the iterative process. In addition, assignment of the lines to start the iterative analysis can be facilitated by considering the dependence of the transitions on the NMR parameters in the simulation stage. LAOCOON 3, modified and extended to handle eight spin systems, has been successfully tested in the iterative analysis of the ¹H NMR spectrum of naphthalene.