The collision of low-energy electrons with neutral atoms and molecules is one of the many processes governing the behavior of the atmospheres surrounding the planets and the tenuous plasmas surrounding comets and planets and their moons. The information on electron collision processes is fragmentary even for the most common atoms and molecules. To improve the information, researchers in SPRL are conducting measurements of these cross sections. The measurements are performed by colliding a monoenergetic beam of electrons with a beam of the particular atoms or molecules of interest. The collisions take place at a right angle and under conditions of extremely high vacuum.
Electrons emerge from the collision at various angles and with a variety of energies.
They are then sorted by specialized detection apparatus according to the angles and energies. The cross sections thus produced provide information crucial to the understanding of atmospheric and plasmaspheric processes. As a byproduct, information is provided which is critical for the understanding of the quantum mechanics of atoms and molecules. Using this technique, the researchers have recently determined the cross sections for excitation of a set of the quantum states of oxygen molecules known as the Schumann-Runge continuum. This new information is of direct consequence to atmospheric and environmental studies.