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Journal of Physical Chemistry A, Vol.102, No.15, 2624-2633, 1998
Electronic structure of dipole-bound anions
Dipole-bound anionic states of HCN, (HF)(2), CH3CN, C3H2, C4H2, C5H2, and stretched CH3F are studied using extended one-electron basis sets at thr coupled cluster level of theory with single, double, and noniterative triple excitations (CCSD(T)). Orbital relaxation and electron correlation corrections to the Koopmans' theorem prediction of electron binding energy an analyzed, and a physical interpretation of low-order corrections is proposed. It is demonstrated that the second-order dispersion interaction between the loosely bound electron and the electrons of the neutral host should be included into physical models of dipole-bound anions. Higher-order electron correlation corrections are also found to be important, and a slow convergence of the Moller-Plesset series for electron binding energies is documented. Modifications of the potential energy surfaces of the above polar molecules upon electron attachment are studied at the second-order Moller-Plesset level, and Franck-Condon factors for the anion/neutral pairs an calculated. It is predicted that photoelectron spectra of the dipole-bound anions of C4H2 and C5H2 should display vibrational structure.
Keywords:FRANCK-CONDON PRINCIPLE;VIBRONIC TRANSITIONS;POLYATOMIC-MOLECULES;DYNAMICAL SYMMETRY;POLAR-MOLECULES;EXCITED-STATES;BASIS-SETS;BINDING;ATOMS;PROPADIENYLIDENE