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Manuscript Title: Photon absorption and scattering cross sections by triaxial nuclei.
Authors: E. Bortolani, G. Maino
Program title: TRIAXI
Catalogue identifier: ACGI_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 70(1992)207
Programming language: Fortran.
Computer: IBM 3090.
Operating system: VM/CMS, VMS.
Word size: 32
Keywords: Nuclear physics, Nuclear reaction, Group theory, Interacting boson model, Nuclear structure, Triaxial shape, Giant dipole resonance, Photoabsorption cross Section, Photon elastic and Inelastic scattering.
Classification: 17.8.

Nature of problem:
A group-theoretical formalism has been developed and implemented in a fast routine in order to deal with photon-induced reactions on triaxial nuclei in the energy region dominated by the giant dipole resonance (GDR), which typically ranges between 10 and 30 MeV. The present approach is based on the interacting boson model of nuclear structure, allowing for coupling between GDR and low-lying collective modes of the nucleus. Isospin degree of freedom can also be included in the calculations. The code computes total photoabsorption cross sections in the GDR region (gamma,p) and (gamma,n) cross sections in the limit of exact isospin symmetry, elastic and inelastic - to the first two 2+ excited levels - photon scattering distributions.

Solution method:
Use is made of group-theoretical techniques to deduce simple expressions for GDR excitation energies and relevant dipole transition strengths; cross sections are then evaluated by means of the usual formalism in terms of nuclear polarizabilities.

The routine assumes a simple form for the low-energy spectrum of triaxial nuclei, corresponding to the exact SU(3) dynamical symmetry of the interacting boson model; moreover, isospin, when included, is assumed to be a good quantum number.

Unusual features:
Use is made of DISSPLA graphics software package in order to plot calculated cross sections and angular distributions. (DISSPLA is a trademark of ISSCO Graphics (Integrated Software Systems Corporation).

Running time:
The evaluation of photon absorption and scattering cross sections by a given nucleus requires less than 10 seconds, including the execution of two plots.