Journal article
Photo-double-ionization of ethylene and acetylene near threshold

Publication Details
Gaire, B.; Lee, S.; Haxton, D.; Pelz, P.; Bocharova, I.; Sturm, F.; Gehrken, N.; Honig, M.; Pitzer, M.; Metz, D.; Kim, H.; Schöffler, M.; Dörner, R.; Gassert, H.; Zeller, S.; Voigtsberger, J.; Cao, W.; Zohrabi, M.; Williams, J.; Gatton, A.; Reedy, D.; Nook, C.; Müller, T.; Landers, A.; Cocke, C.; Ben-Itzhak, I.; Jahnke, T.; Belkacem, A.; Weber, T.
Publication year:
Physical Review A
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Journal acronym:
Phys. Rev. A
Volume number:

We present kinematically complete measurements of the photo-double-ionization of ethylene (double CCbond) and acetylene (triple CC bond) hydrocarbons just above the double-ionization threshold. We discuss theresults in terms of the coincident kinetic energy of the photoelectrons and the nuclear kinetic-energy release of therecoiling ions.We have incorporated quantum chemistry calculations to interpret which of the electronic states ofthe dication have been populated and trace the various subsequent fragmentation channels.We suggest pathwaysthat involve the electronic ground and excited states of the precursor ethylene dication and explore the stronginfluence of the conical intersections between the different electronic states. The nondissociative ionization yieldis small in ethylene and high in acetylene when compared with the dissociative ionization channels. The reasonfor such a striking difference is explained in part on the basis of a propensity rule that influences the populationof states in the photo-double-ionization of a centrosymmetric closed-shell molecule by favoring singlet ungeradeand triplet gerade final states. This propensity rule and the calculated potential-energy surfaces clarify a pictureof the dynamics leading to the observed dication dissociation products.


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