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276. MOSSBR: Curve-Fitting Program for Mössbauer Spectra
by A. J. Stone, University Chemical Laboratory, Lensfield Road, Cambridge, England MOSSBR fits a set of Lorentzian lines to an experimental Mössbauer spectrum, using the Gauss-Newton least-squares procedure. The main feature of this program is the ability to constrain any parameter or linear combination of parameters; the fitting process is carried out in a number of stages, and at each stage the constraints can be changed, usually by removing some or all of the constraints enforced in the previous stage. This procedure is a powerful aid in fitting complex spectra, where attempts at an unconstrained fit normally lead to divergence or very slow convergence, depending on the least-squares algorithm used. It also provides a simple means of introducing information, such as the positions of impurity lines, which may be known in advance much more accurately than the data could determine them; and it yields a convenient criterion for evaluating the statistical significance of phenomena such as differences in intensity between the two lines of a quadrupole doublet. The normal version, SINGLET, of the program fits a number of single Lorentzian lines, but other versions are provided which fit a number of quadrupole doublets or a number of magnetic sextets more efficiently than would be the case for the SINGLET program with the appropriate constraints.The program has been extensively tested in use over a period of more than six years. The language used is close to ANSI FORTRAN, but uses a small number of IBM 360/370 language extensions. Lines of Code: 2636 (including 700 COMMENT cards) Recommended Citation: A. J. Stone, QCPE 11, 274 (1975). |