Band Spectrum Intensities for Symmetrical Diatomic Molecules. II

In a previous paper the writer derived an approximate expression for intensities in the electronic vibrational bands of symmetrical diatomic molecules, based upon the Franck-Condon theory of transition probabilities. In the present paper the approximation is carried further, by removing the restriction that the oscillations be linear. An extended formula is given making use of the Schr\"odinger theory of perturbations.Calculations using this perturbation theory formula are carried out for the hydrogen absorption band spectrum. It is shown that the agreement with experiment is much improved over that obtained on the assumption of harmonic oscillations. Calculations are also made using Morse's potential function in which case the agreement is still further improved, especially for the higher transitions.