Struktura elektronowa anionów związanych dipolowo

Recent photodetachment, photoelectronspectroscopy, and charge transfer collision studies of dipole-bound anions revealed deficiencies in theoretical predictions based on the electrostatic model. The experimental electron binding energies were much larger than theoretical estimations obtained at the Koopmans' theorem or self-consistent field levels. Moreover, photoelectron spectra of dipole-bound anions frequently display vibrational structure whereas a common view was that a dipole-bound anion may be regarded as a neutral molecule with the excess distant electron tethered so weakly to the dipole that the equilibrium geometries of the neutral and the anion are practically the same and therefore no vibrational structure was anticipated on the basis of Franck-Condon factors. In this review we summarize our recent work on electron binding energies in dipole-bound anions as well as on molecular relaxation upon electron attachment. We demonstrate that electron correlation effects contribute significantly to electron binding energies. In particular the dispersion interaction between the excess electron and electrons of the neutral molecule was recognized as a sizable stabilizing contribution. The molecular relaxation upon electron attachment was found to be significant and clearly detectable for hydrogen bonded clusters and small but still noticeable for some valence bonded polar molecules.