Electron transfer processes in binary van der Waals clusters via the N2−(2Πg) resonance

Free-electron attachment in the energy range 0–4 eV to binary van der Waals clusters composed of N2/SF6 and N2/O2 is studied with high resolution (< 0.1 eV). In the gas phase SF6 accepts electrons near 0 eV and O2 in the energy range around 0.5 eV. While SF6− is long-lived and can easily be observed by mass spectrometry, the lifetime of O2− is in the ps range and thus far off mass spectrometric detection. Electron attachment to mixed clusters, on the other hand, leads to stable ionic complexes of the form (SF6)n− and (O2)n−, n = 1, 2, … These ions appear at low energy, but also within a resonant feature near 2.3 eV indicating that the N2−(2Πg) resonance acts as an effective electron transfer state in clusters. The experimental results show that in clusters the electronic energy of the ‘chromophore’ N2−(2Πg) is quickly dispersed among the target cluster thus allowing effective electron transfer. Effective intermolecular energy dispersion also removes any possible vibrational structure in the energy-dependent cross section of the final ionic products.