Title of program: HFNX Method of solution Transition probabilities in the allowed decay modes of the Catalogue number: ABVV compound nucleus are calculated (using level density functions wherever the final states are not experimentally identi-Program obtainable from: CPC Program Library, Queen's fied), from values of neutron strength functions supplied to University of Belfast, N. Ireland (see application form in this the program. The cross-sections are then calculated from the issue) HF formula [1] modified by the width fluctuation correction [2]. The procedure is repeated for a set of incident energies, Computer: ICL 2980; Installation: Oxford University Corn-and again for such excited target states as are necessary; the puting Service (n, y) cross-sections obtained are averaged over thermal populations of these states to give astrophysical reaction rates [3] Operating system: VME/B at required temperatures. Programming language used: FORTRAN IV Restrictions on the complexity of the problem High speed storage required: 16 Kwords States with spins from 0 to 10, 1/2 to 2 1/2, can be included. Excited target states are not automatically provided within No. of bits in a word: 64 the program by a level density formula, and must be explicitly described to the program. El, Ml and E2 electrornag-Overlay structure: none netic transitions are included. El transitions are assumed to proceed through a giant dipole resonance [2]. Isotopic spin No. of magnetic tapes required: none effects are not allowed for. Other peripherals used: card reader Typical running time Cards in combined program and test deck: 1038 Depends on target spin, numbers ofscattering and excited target states, and temperature range considered. For tempera-Card punch code: ICL tures up to 3 X i0 9 K, in the most favourable case (0~target, no inelastic scattering or excited target states), typically 3 mm on the OUCS ICL 2980.