Calculations

The idea behind the experiment is to measure the cross sections of molecules for certain excitations.

This measurement must be made indirectly.  The experiment makes this measurement in the following way:

1. Monoenergetic electrons pass through the target gas (NO).
2. Nitric oxide molecules can be excited by the projectle electrons.
3. The excited molecules emit light as they decay from the excited state
4. We detect this emitted light.
5. The intensity of the light detected is related to the size of the cross sections.

The larger the cross section, the more molecules were excited by the electron and the greater the intensity of light emitted (see fig. 4)

We are currently measuring aobsolute emission cross sections for electron-impact excitation of the NO system and their energy dependence.

Optical Method

The emission signal from the excited molecules, S_emission, is related to the cross section by where

	efficiency of the detection optics and detector
	solid angle subtended by the collection optics
	target density
	electron-beam flux

and the integral is over the interaction volume viewed by the detection optics.

We determine the efficiency of the detection optics and detector by substituting a calibrated lamp for the molecular emission signal.

The nitric oxide molecular beam emerges from an array of capillary tubes. To determine the target density we use a molecular flow model.

We determine the electron beam flux by translating a thin wire across the diameter of the electron beam. We can use an Abel transform to convert this one-dimensional beam "profile" into a cylindrically symmetric function, .

Layout and Design: Andrew A. Kucheriavy