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Manuscript Title: Vibrational energies of CO2.
Authors: W.C. Maguire
Program title: VIBOCO
Catalogue identifier: ABWC_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 10(1975)368
Programming language: Fortran.
Computer: IBM 360/91.
Operating system: OS/360.
RAM: 10K words
Word size: 32
Keywords: Molecular physics, Vibrational energy, Carbon dioxide, Infrared transmission, Fermi resonance, Planetary, Atmosphere.
Classification: 16.3.

Nature of problem:
Atmospheric temperature profiles and pressure values for planetary atmospheres can be determined using infrared spectra. Carbon dioxide bands observed in the spectra of planets are conveniently used for such calculations. Consequently, theoretical energy levels of this molecule, including various isotopic species, are required.

Solution method:
A molecular hamiltonian describing carbon dioxide, which is a linear triatomic, is diagonalized. The effect of Fermi reasonance is considered. The vibrational energies and rotational constants as well as mixing coefficients are obtained for levels from the ground state (v1,v2,v3;l) = (0,0,0,0) to the energy level (0,24,0;24). Here vi is is the vibrational quantum number associated with the ith normal mode and l is the angular momentum quantum number.

Only vibrational levels having unperturbed energy less than the energy of a state (v1,v2,v3;l) = (0,24,0;24) (see long write-up) are considered. For the main isotope 16O12C16O with a ground-state energy at 2534.682 cm-1 the energies range up to slightly more than 20000 cm-1.

Running time:
A complete run for one isotope, consisting of more than 1800 energy levels, associated mixing coeficients and rotational constants takes less than a minute on an IBM 360/91.