  Isotope effects associated with gas phase N2 photolysis are used to interpret
Martian atmospheric evolution, icy satellite atmospheric chemistry and
meteorite isotopic anomalies from nebular N2 photochemistry. To interpret
observations at the highest level, fundamental understanding of the precise
wavelength dependency of the process must be known. In this paper VUV isotopic
photodissociation effects are calculated as a function of wavelength at
different wavelength slices in the 12.5-15 eV range. A very strong wavelength
dependence is observed, which is significant for experiments. An observable
effect is possible for the width of the beam profile at the advanced light
source, ALS that may produce sufficient photolysis product for high precision
isotopic analysis. A significantly more pronounced effect is predicted for a
beam narrower by a factor of four providing a potential experimental test of
the model. The spectrum is computed ab initio. It manifests two physical
mechanisms for the isotope effect and they can be discriminated using a narrow
beam. The fractionation is larger for the rarer heaviest isotopomer 15N15N and
half as large for 15N14N.
