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 parts per thousand, in the solar wind and Jovian atmosphere, to about 5,000 parts per thousand 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 N-2 photolysis at vacuum UV wavelengths in the presence of hydrogen are presented here, which show a wide range of enriched delta N-15 values from 648 parts per thousand to 13,412 parts per thousand in product NH3, depending upon photodissociation wavelength. The measured enrichment range in photodissociation of N-2, plausibly explains the range of delta N-15 in extraterrestrial materials. This study suggests the importance of photochemical processing of the nitrogen reservoirs within the solar nebula.