CONTRIBUTION OF ELECTRON CORRELATION TO THE STABILITY OF DIPOLE-BOUNDANIONIC STATES

It has long been assumed that electron correlation effects are relativ ely unimportant for describing dipole-bound anionic states. It is show n here that this assumption is incorrect: high-level electronic struct ure calculations on the dipole-bound anion states of CH3CN, C3H2, and C5H2 reveal that for these species a large fraction of the electron bi nding energy derives from the dispersion-type interaction between the loosely bound electron and the neutral molecule. The predicted values of the electron affinities of the dipole bound states of CH3CN and C3H 2. 108 and 173 cm(-1), respectively, are in excellent agreement with t he recent experimental results, 93 cm(-1) and 171 +/- 50 cm(-1), respe ctively. The predicted value for C5H2 is 614 cm(-1).