Cluster size effects upon anion solvation of N-heterocyclic molecules and nucleic acid bases

Rydberg electron transfer spectroscopy is used for the experimental determi nation of slightly negative electron affinities of N-heterocyclic molecules , pyridine, pyridazine, pyrimidine, pyrazine and DNA bases, adenine, cytosi ne, thymine and uracil. These molecules are solvated inside clusters of rar e gases, water, ammonia or toluene in order to stabilize their anions again st autodetachment, and the anion formation process is studied as a function of the number of solvent atoms or molecules. Determination of the cluster size thresholds above which valence anions are observed provides estimation s of the electron affinities which are compared with the results of other e xperimental or theoretical determinations. (C) 2000 Elsevier Science BN. Al l rights reserved.