ELECTRON-TRANSFER PROCESSES IN BINARY VAN-DER-WAALS CLUSTERS VIA THE N-2(-)((2)PI(G)) RESONANCE

Free-electron attachment in the energy range 0-4 eV to binary van der Waals clusters composed of N-2/SF6 and N-2/O-2 is studied with high re solution (< 0.1 eV). In the gas phase SF6 accepts electrons near O eV and O-2, in the energy range around 0.5 eV. While SF6- is long-lived a nd can easily be observed by mass spectrometry, the lifetime of O-2(-) is in the ps range and thus far off mass spectrometric detection. Ele ctron attachment to mixed clusters, on the other hand, leads to stable ionic complexes of the form (SF6)(n)(-) and (O-2)(n)(-) n = 1, 2,... These ions appear at low energy, but also within a resonant feature ne ar 2.3 eV indicating that the N-2(-)((IIg)-I-2) resonance acts as an e ffective electron transfer state in clusters. The experimental results show that in clusters the electronic energy of the 'chromophore' N-2( -)((IIg)-I-2) is quickly dispersed among the target cluster thus allow ing effective electron transfer. Effective intermolecular energy dispe rsion also removes any possible vibrational structure in the energy-de pendent cross section of the final ionic products.