The true diatomic potential as a perturbed Morse function

✍ Scribed by Mounzer Dagher; Mounif Kobersi; Hafez Kobeissi

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 384 KB
• Volume: 16
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/jcc.540160608

✦ Synopsis

The problem of representing a diatomic (true) Rydberg-Klein-Rees potential U ' by an analytical function U" is discussed. The perturbed Morse function is in the form U" = U M + Cb, y", where the Morse potential is U M = Dy2, y = 1exp( -a(rre)). The problem is reduced to determination of the coefficients b, so UYr) = U ' ( r ) . A standard least-squares method is used, where the number N of b, is given and the average discrepancy n = I(U' -U a ) / U ' I is observed over the useful range of r. N is varied until n is stable. A numerical application to the carbon monoxide X 'C state is presented and compared to the results of Huffaker' using the same function with N = 9. The comparison shows that the accuracy obtained by Huffaker is reached in one model with N = 5 only and that the best is obtained for N = 7 with a gain in accuracy. Computation of the vibrational energy E, and the rotational constant B,, for both potentials, shows that the present method gives values of and a that are smaller than those found by Huffaker. The dissociation energy obtained here is 2.3% from the experimental value, which is an improvement over Huffaker's results. Applications to other molecules and other states show similar results.