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

Rydberg electron transfer spectroscopy is used for the experimental determination of slightly negative electron affinities of N-heterocyclic molecules, pyridine, pyridazine, pyrimidine, pyrazine and DNA bases, adenine, cytosine, thymine and uracil. These molecules are solvated inside clusters of rare gases, water, ammonia or toluene in order to stabilize their anions against 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 estimations of the electron affinities which are compared with the results of other experimental or theoretical determinations. (C) 2000 Elsevier Science BN. All rights reserved.