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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.

Restrictions:
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.