Electron interactions are well known to drive much of the physics and chemistry that is important in our everyday lives. These processes extend from gas discharge-based lights and lasers, plasma processing technologies, pollution remediation and atmospheric and astrophysical phenomena. In all cases, low energy electron impact of atoms and molecules plays a crucial role, either as a pre-cursor in a complex chain of interactions, or as the main driving mechanism.

In this talk we shall provide an example of how ‘microscopic’ electron collision processes, on the angstrom scale, can drive large-scale processes in our upper atmosphere. We shall use electron impact excitation of the NO molecule as a particular example. NO can form a stable negative ion, which supports long-lived vibrationally excited levels as well as several low-lying electronically excited levels. These excited levels are readily populated by low energy electron scattering. A number of recent experiments from our group [1,2], and others [3] have demonstrated and quantified, for the first time, that when the negative ion decays, there is a strong propensity for leaving the neutral molecule in a vibrationally excited level (NO*).

We have used these recent absolute cross section measurements, in conjunction with statistical equilibrium simulations [4], to model the role that electron-driven processes play in infra-red emissions from NO in the earth’s aurora. Previous work, which did not have access to these new cross section measurements, had indicated that the dominant mechanism for formation of NO*, was chemiluminescence, whereby excited nitrogen atoms collide with oxygen molecules to form the NO*. However, the present studies [5] show that electron impact may be responsible for as much as 30% of the excited NO* found in the auroral regions. Details of the experimental measurements, a brief account of the model, and its results, will be presented.

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