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Manuscript Title: A Fortran program to interpret pulsed field-gradient spin-echo diffusion data.
Authors: E.D. von Meerwall
Program title: DIFFUS2
Catalogue identifier: ABNE_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 17(1979)309
Programming language: Fortran.
Computer: IBM 370/158.
Operating system: OS/MVS.
RAM: 10K words
Word size: 32
Keywords: Nuclear physics, Molecular, General experiment, Nuclear magnetic Resonance, Spin echo, Pulsed magnetic field Gradient method, Steady gradient method, Science polymer, Diffusion.
Classification: 17.4.

Nature of problem:
NMR spin echo attenuation of the diffusing species, caused by steady and pulsed magnetic field gradients, is interpreted in terms of diffusion constants.

Solution method:
Various least-squares techniques are used to find the diffusion constant, and optionally, the constant spin echo of a non-diffusing species and to detect deviations from the model. Comprehensive error analysis and plot are provided.

The present limit of 40 data points is easily extended.

Unusual features:
(1) Three or more data points (spin echo height +- error vs. field gradient pulse length) are required for a least-squares determination of diffusion coefficient;
(2) arbitrary diffusing nuclear species, steady and pulsed field gradients, and rf and gradient pulse timings are accommodated;
(3) non-diffusing nuclear species can be accounted for, and true multi- component diffusion and restricted diffusion can be detected;
(4) a full error analysis coupled with chi-square considerations provides uncertainties of all derived parameters and checks the applicability of the selected model. A plot of data and fit is provided on the line printer.

Running time:
On the IBM 370/158 III, the program compiles (G1 compiler) in about 6 s CPU; a single case with full analysis takes slightly over 1 s CPU.