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Manuscript Title: A Fortran program for reduction of NMR relaxation data.
Authors: E.D. von Meerwall, D. Thompson
Program title: T12FIT
Catalogue identifier: ACFT_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 31(1984)385
Programming language: Fortran.
Computer: IBM 3033.
Operating system: OS/MVS/SE.
RAM: 86K words
Word size: 32
Keywords: Solid state physics, Experiment, Resonance, Spin-spin, Least-squares fit, Relaxation time, Rotating frame, Nuclear magnetic Spin-lattice, Carr-purcell.
Classification: 7.4.

Nature of problem:
NMR relaxation data (free induction decay or spin echo amplitude vs. time) is automatically interpreted in terms of one or two relaxation rates.

Solution method:
Chi-square criteria based on experimental uncertainties are used to decide whether relaxation follows a single expotential or Gaussian model, or whether an additional slow expotential component is present. Output includes relaxation times and relative component intensities with their uncertainties, chi-square goodness of fit, and plot of data and fitted model.

Restrictions:
The limit of 50 data points is easily removed by redimensioning and altering one loop parameter. The strategy may be extended to more than two relaxation components and to alternate relaxation models.

Unusual features:
(1) Program processes data from Tl,Tlp,and T2 (spin-echo, Carr-Purcell or Meiboom-Gill methods) experiments;
(2) Program decides whether relaxation has one or two components, and whether the fast-relaxing component is expotential or (for T2 relaxation) Gaussian.
(3) Core of program is small enough to fit on typical spectrometer computer for on-line data reduction.

Running time:
On the IBM 3033U, compilation takes 1.4 s CPU time. Typical cases with 30 data points are analyzed in approximately 0.5 s CPU time.