ADHESION OF AGI MOLECULES TO GASEOUS METALLIC SILVER CLUSTER CATIONS

The evaporative channels for the unimolecular dissociation of metastab le Ag(X)I(Y)+ (X = 5-25; Y = 0-4) clusters made by fast atom bombardme nt of silver foil in the presence of CH3I vapor are observed in the fi rst field-free region of a double-focusing mass spectrometer. We found three dominant neutral evaPorative channels: Ag loss, Ag2 loss, and A gI loss. Only Ag12I3+ is found to have an additional channel involving an (AgI)3 loss. Consistent with our previous studies of stable Ag(X)I (Y)+ clusters, we assume a structural formula of (Ag(X-Y))+(AgI)Y, whe re the metallic part of the cluster conforms to Jellium model predicti ons. In comparing the relative evaporative loss of AgI from these meta stable clusters, we observe: (a) evidence for significant AgI-AgI inte raction for clusters whose metallic part has a 1s2, 1p2, or 1s(2)1p4 J ellium configuration; (b) a near constant fractional loss of AgI as th e number of AgI units in the parent cluster increases for clusters who se metallic part has a closed main Jellium shell; (c) a relative incre ase in the fraction loss of AgI as the number of AgI molecules in the parent cluster increases for clusters with an ''open''-shell configura tion for the metallic part. These observations are discussed in terms of evaporative loss of AgI from structures in which the AgI molecules solvate the metallic part of the cluster. It is proposed that the heat of AgI evaporation is greatly determined by dipole/induced-dipole int eractions between the permanent dipole of AgI and the polarizable delo calized electron density of the metallic part of the cluster.