THE DIPOLE BOUND-TO-COVALENT ANION TRANSFORMATION IN URACIL

Nucleic acid base anions play an important role in radiation-induced m utagenesis. Recently, it has been shown that isolated (gas-phase) nucl eobases form an exotic form of negative ions, namely, dipole bound ani ons. These are species in which the excess electrons are bound by the dipole fields of the neutral molecules. In the condensed phase, on the other hand, nucleobase anions are known to be conventional (covalent) anions, implying the transformation from one form into the other due to environmental (solvation) effects. Here, in a series of negative io n photoelectron spectroscopic experiments on gas-phase, solvated uraci l cluster anions, we report the observation of this transformation. (C ) 1998 American Institute of Physics.