THEORETICAL-STUDY OF THE DIPOLE-BOUND ANION (HF)(2)(-)

It has long been assumed that dipole-bound anionic states possess two properties;,(i) the electron binding energy is dominated by the electr ostatic electron-dipole interaction, and (ii) the geometrical distorti on of the polar molecule upon attachment of a distant electron is negl igible. Our results indicate, however, that the dispersion interaction between the loosely bound electron and the electrons of the neutral d imer is as important as the electrostatic electron-dipole stabilizatio n. In addition, the hydrogen bond in (HF) is susceptible to a deformat ion upon attachment of a distant electron. This deformation enhances b oth the electrostatic and dispersion components of the electron bindin g energy. The calculated Franck-Condon factors indicate that neutral d imers formed in electron photodetachment experiments may be vibrationa lly excited in both stiff intramolecular HF stretching modes and soft intermolecular modes. The predicted value of the adiabatic electron de tachment energy for (HF)(2)(-) is 396 cm(-1) and the theoretical photo electron spectrum is in remarkable agreement with the experimental dat a of Bowen et. al. J. H. Hendricks, H. L. de Clercq, S. A. Lyapustina, and K. H. Bowen, Jr. [J. Chem. Phys. 107, 2962 (1997)]. (C) 1997 Amer ican Institute of Physics.