|
378. DAVINS: Direct Analysis of Very Intricate NMR
Spectra
by David S. Stephenson and Gerhard Binsch, Institute of Organic Chemistry, The University of Munich, Munich, West Germany DAVINS is a flexible and efficient computer program for the fully automated analysis of high-resolution NMR spectra.It extracts chemical shifts, indirect coupling constants and the linewidth from an experimental spectrum consisting of n (N < 10200) digitized signal intensities, recorded in CW or FT mode. The raw spectral data may be subjected to several stages of pretreatment, including data format conversion, pretruncation, noise calculation, baseline flattening, smoothing and post-truncation. The resulting preprocessed experimental spectrum, the specification of the spin system, a set of trial spectral parameters and a number of control constants represent the starting point of an iterative least- squares calculation for which no assignments of energy levels or transitions are necessary (or indeed, possible). The algorithm has the capability to home in on the global minimum of the least-squares functional in the presence of a multitude of false local minima and is designed to do so efficiently and without the possibility of divergence. In the majority of cases, DAVINS will produce the correct solution from starting trial parameters chosen randomly within specified boundaries in a single pass; in difficult cases of extremely tightly coupled spectra, more than one pass through DAVINS may be required. In addition to the standard input mode, in which n 16-bit integer data words are read from a 9-track magnetic tape prepared by an NMR instrument computer, three optional alternative input routines are provided: (a) tape simulation card input; (b) card input of hand-digitized spectra; (c) input of line frequencies and intensities on cards. The program outputs information about the progress of the iteration, the final parameters, a complete error analysis and two types of global agreement factors, and optionally produces plots of the original, the preprocessed experimental and the computer spectra, either on separate sheets or as superimposed traces. DAVINS may also be used for spectral synthesis only and for generating output of digitized synthetic spectral data. NOTE: This system was developed using the CDC NOS operating system. NOS assumes a segment loader as opposed to the usual OVERLAY loader found in many CDC operating systems. FORTRAN IV EXTENDED (CDC) Lines of Code: 3501 Recommended Citation: D. S. Stephenson and G. Binsch, QCPE 11, 378 (1979). |