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Manuscript Title: TRIATOM, SELECT and ROTLEV: for the calculation of the ro-vibrational levels of triatomic molecules.
Authors: J. Tennyson
Program title: ROTLEV
Catalogue identifier: AALQ_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 42(1986)257
Programming language: Fortran.
Computer: CRAY-1.
Peripherals: disc.
Keywords: Molecular physics, Vibration, Rotationally excited State, Coriolis coupling, Secondary variational Method.
Classification: 16.3.

Subprograms used:
Cat Id Title Reference
AALO_v1_0 TRIATOM CPC 42(1986)257

Nature of problem:
ROTLEV performs the second step in a two-step variational calculation for the bound ro-vibrational levels of a triatomic system, especially those with large total angular momentum, using the generalised body- fixed coordinates developed by Sutcliffe and Tennyson.

Solution method:
A basis is constructed from Coriolis decoupled solutions of the problem. The resulting sparse secular matrix is then diagonalised to give the solutions.

The size of the matrix that can practically be diagonalised. ROTLEV allocates arrays dynamically at execution time and in the present version the total space available is a single parameter which can be preset as required.

Unusual features:
Most of the data input is read in directly from TRIATOM.

Running time:
Case dependent. A problem with 902 basis functions takes 20 seconds on the CRAY-1.