Formation of NO− following electron attachment to NO clusters

Low-energy (0–1 eV) electron attachment to NO clusters is studied with high-energy resolution (15 meV, FWHM). The dominant signal is NO− which has not been observed in previous Rydberg electron transfer studies to NO clusters. The relative cross-section for NO− formation shows a sharp peak close to 0 eV and a series of further weak peaks with a spacing of about 190 meV. The `0 eVʹ peak is ascribed to `s-wave captureʹ by the entire target cluster. Due to the low adiabatic electron affinity of NO (26 meV), NO− cannot be the result of an evaporative attachment reaction. It is suggested that neutral products like N2, via the strongly bound (ONNO)− intermediate, are involved. The weak structures are tentatively assigned as arising from transitions to vibrational excited states of solvated NO−.