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Manuscript Title: Calculation of (n, gamma) cross-sections and astrophysical reaction rates by the nuclear statistical model.
Authors: M.J. Harris
Program title: HFNX
Catalogue identifier: ABVV_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 21(1981)407
Programming language: Fortran.
Computer: ICL 2980.
Operating system: VME/B.
RAM: 16K words
Word size: 64
Keywords: Nuclear physics a, Strophysics, Theoretical methods, Low energy s, Tatistical model, Giant dipole resonance, Cross-sections e, Lectro Magnetic transitions, Width fluctuation r, Eactions, Nuclear processes, Activity detection.
Classification: 17.6, 17.16.

Nature of problem:
Calculation of (eta,gamma) cross-sections for large numbers of target nuclei with A greater than 50 by the Hauser-Feshbach (HF) method. Calculation of astrophysical nuclear reaction rates, allowing for thermal population of excited states of the target.

Solution method:
Transition probabilities in the allowed decay modes of the compound nucleus are calculated (using level density functions wherever the final states are not experimentally identified), from values of neutron strength functions supplied to the program. The cross-sections are then calculated from the HF formula modified by the width fluctuation correction. The procedure is repeated for a set of incident energies, and again for such excited target states as are necessary; the (n,gamma) cross-sections obtained are averaged over thermal populations of these states to give astrophysical reaction rates at required temperatures.

Restrictions:
States with spins from 0 to 10, 1/2 to 21/2, can be included. Excited target states are not automatically provided within the program by a level density formula, and must be explicitly described to the program. E1, M1 and E2 electromagnetic transitions are included. E1 transitions are assumed to proceed through a giant dipole resonance. Isotopic spin effects are not allowed for.

Running time:
Depends on target spin, numbers of scattering and excited target states, and temperature range considered. For temperatures up to 3 X 10**9K, in most favourable case (0+ target, no inelastic scattering or excited target states), typically 3 min on the OUCS ICL 2980.