Nitrogen isotopic fractionations in the low temperature (80 K) vacuum ultraviolet photodissociation of N₂

N ₂ is a diatomic molecule with complex electronic structure. Interstate crossings are prominent in the high energy domain, introducing significant perturbations to the system. Nitrogen mainly photodissociates in the vacuum ultraviolet (VUV) region of the electromagnetic spectrum through both direct and indirect predissociation. Due to the complexity introduced by these perturbations, the nitrogen isotopic fractionation in N ₂ photodissociation is extremely hard to calculate, and an experimental approach is required. We present new data of N-isotopic fractionation in N ₂ photodissociation at low temperature (80 K), which shows a distinctly different15N enrichment profile compared to that at relatively higher temperatures (200 and 300 K). The new data, important to understanding the N-isotopic compositions measured in meteorites and other planetary bodies, are discussed in light of the knowledge of N ₂ photochemistry and calculated photoabsorption cross sections in the VUV. Authors: