TEMPERATURE DEPENDENCE OF DISSOCIATIVE ATTACHMENT IN N2O

The attachment of low-energy electrons (<4 eV) by the reaction e+N 2O → O- +N2 has been studied as a function of gas temperature from approximately 160 to 1040°K. The ions produced by a monoenergetic electron beam are detected by total ion collection or by mass analysis. The kinetic energy distributions of the O- ions have also been measured and found to be relatively insensitive to the electron energy when the latter exceeds 1.5 eV, in which case the most probable ion energy is 0.38 eV. The shape and magnitude of the cross section below 2 eV is found to be sensitive to gas temperature throughout the range studied. The differences in shape and threshold observed by previous workers occur below 2 eV and to a large extent may be reconciled in terms of the differing gas temperatures employed. The temperature insensitive portion of the cross section is ascribed to electron capture into the highest-energy N2O- state connected to electronic ground state N2+O-. The O- kinetic energy distributions arising therefrom are explained in terms of the N 2O- potential energy surface involved. It is argued that the strongly temperature sensitive portion of the cross section is due predominantly to excitation of the bending mode of vibration, and arises from the dependence on bond angle of the separation in energy of the electronic ground states of N2O and N2O-.