AUTHOR=Hrodmarsson Helgi R. , Thissen Roland , Dowek Danielle , Garcia Gustavo A. , Nahon Laurent , Govers Thomas R. TITLE=Isotope Effects in the Predissociation of Excited States of N2+ Produced by Photoionization of 14N2 and 15N2 at Energies Between 24.2 and 25.6 eV JOURNAL=Frontiers in Chemistry VOLUME=7 YEAR=2019 URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2019.00222 DOI=10.3389/fchem.2019.00222 ISSN=2296-2646 ABSTRACT=

Photoelectron/photoion imaging spectrometry employing dispersed VUV radiation from the SOLEIL synchrotron has been used to study the predissociation of N₂⁺ states located up to 1.3 eV above the ion's first dissociation limit. Branching ratios for unimolecular decay into either N₂⁺ or N⁺ were obtained by measuring coincidences between threshold electrons and mass-selected product ions, using a supersonic beam of either ¹⁴N₂ or ¹⁵N₂ as photoionization target. The results confirm that predissociation of the C2Σu+ state of ¹⁴N₂⁺ is faster than emission to the electronic ground-state by a factor 10 or more for all vibrational levels v′ ≥ 3, while for ¹⁵N₂⁺ the two decay modes have comparable probabilities for the levels v′ = 3, 4, and 5. In contrast, no significant isotope effect could be observed for the other states of N₂⁺ identified in the photoelectron spectrum. For both ¹⁴N₂⁺ and ¹⁵N₂⁺ isotopologues all vibrational levels of these other states decay to an extent of at least 95% by predissociation.