Electron attachment to van der Waals polymers of carbon dioxide and nitrous oxide

Negative ions formed by electron attachment to carbon dioxide and nitrous oxide, expanded through a sonic nozzle, are reported. In each case the dominant ions have the formula O−(M)n, where M is the parent monomer. The appearance potential of O− in each case indicates the absence of ’’hot bands.’’ Ions with the formula (CO2)−n, with n?2, evidently formed by evaporative electron attachment, seem to be stable with respect to autodetachment. The ’’three-body’’ mechanism for attachment of thermal electrons to nitrous oxide and oxygen is discussed.