Application of the Pariser and Parr Method to Dye Ions with Amidinium Resonance

The transition energies and transition probabilities for the family of dye ions Me2N–(CH=CH)n−1–CH=N lim +Me2are calculated using the method of Pariser and Parr. The nitrogens are taken into account by a perturbation method. Configuration interaction considering single excitations from the ground configuration is employed, though in the comparison with experiment it is judged better to use the diagonal matrix elements for the transition energies.