Massive isotopic effect in vacuum UV photodissociation of N₂ and implications for meteorite data

Nitrogen isotopic distributions in the solar system extend across an enormous range, from -400‰, in the solar wind and Jovian atmosphere, to about 5,000‰ in organic matter in carbonaceous chondrites. Distributions such as these require complex processing of nitrogen reservoirs and extraordinary isotope effects. While theoretical models invoke ion-neutral exchange reactions outside the protoplanetary disk and photochemical self-shielding on the disk surface to explain the variations, there are no experiments to substantiate these models. Experimental results of N₂ photolysis at vacuum UV wavelengths in the presence of hydrogen are presented here, which show a wide range of enriched δ15N values from 648‰to 13,412‰in product NH₃, depending upon photodissociation wavelength. The measured enrichment range in photodissociation of N₂, plausibly explains the range of δ¹⁵N in extraterrestrial materials. This study suggests the importance of photochemical processing of the nitrogen reservoirs within the solar nebula.