Larsen, Kirk A.Rescigno, Thomas N.Severt, TravisStreeter, Zachary L.Iskandar, WaelHeck, SaijoschaGatton, AverellChampenois, Elio G.Strom, RichardJochim, BethanyReedy, DylanCall, DemitriMoshammer, RobertDörner, ReinhardLanders, Allen L.Williams, Joshua B.McCurdy, C. WilliamLucchese, Robert R.Ben-Itzhak, ItzikSlaughter, Daniel S.Weber, Thorsten2023-12-072023-12-072020-10-09https://hdl.handle.net/2097/44069We report measurements on the H++H+ fragmentation channel following direct single-photon double ionization of neutral NH3 at 61.5 eV, where the two photoelectrons and two protons are measured in coincidence using three-dimensional (3D) momentum imaging. We identify four dication electronic states that contribute to H++H+ dissociation, based on our multireference configuration-interaction calculations of the dication potential energy surfaces. The extracted branching ratios between these four dication electronic states are presented. Of the four dication electronic states, three dissociate in a concerted process, while the fourth undergoes a sequential fragmentation mechanism. We find evidence that the neutral NH fragment or intermediate NH+ ion is markedly rovibrationally excited. We also identify differences in the relative emission angle between the two photoelectrons as a function of their energy sharing for the four different dication states, which bare some similarities to previous observations made on atomic targets.Creative Commons Attribution 4.0 International licensehttps://creativecommons.org/licenses/by/4.0/Text