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Manuscript Title: Rovibrational cross sections from reactance matrices calculated in adiabatic nuclei approximation.
Authors: R.J.W. Henry
Program title: VIBAD
Catalogue identifier: ACWI_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 10(1975)375
Programming language: Fortran.
Computer: CDC 6400.
Operating system: SCOPE.
RAM: 40K words
Word size: 60
Keywords: Molecule, Scattering, Electron-molecule, Cross section, Reactance matrix, Adiabatic nuclei Approximation, Rotational, Racah coefficient.
Classification: 16.5.

Nature of problem:
Body frame reactance matrices obtained from elastic scattering calculations at fixed internuclear separations are transformed into laboratory frame matrices to compute differential and integral cross sections for simultaneous rotational and vibrational excitation of a molecule.

Solution method:
Transformation for vibrational excitation is obtained by integrating the real and imaginary parts of the body-frame t-matrices over interbuclear separation. Vibrational wave functions are assumed to be given. The rotational transformation involves an eight-fold sum over angular momenta. The summands involve A lambda-coefficients and Legendre polynomials, which are each evaluated by separate subprograms. differential, integral, and momentum transfer cross sections are computed from the transformed t-matrices.

The array lengths should be adjusted to suit the user's problem and the core available on his computer. The algebraic transformations may introduce numerical inaccuracies for angular momenta > 15, if single precision is used on a machine with shorter word length.

Running time:
The sample data, comprising one energy, 8 internuclear separations, and electron orbital angular momenta <= 3, took 14 s CPU time.