Vibrationally mediated photodissociation of ethylene cation by reflectron multimass velocity map imaging

Myung Hwa Kim, Brian D. Leskiw, Arthur G. Suits

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A new imaging technique, reflection multimass velocity map ion imaging, is used to study the vibrationally mediated photodissociation dynamics in the ethylene cation. The cation ground electronic state is prepared in specific vibrational levels by two-photon resonant, three-photon ionization via vibronic bands of (π, nf) Rydberg states in the vicinity of the ionization potential of ethylene, then photodissociated through the (B̃ 2A g) excited state. We simultaneously record spatially resolved images of parent C 2H 4 + ions as well as photofragment C 2H 3 + and C 2H 2 + ions originating in dissociation from the vibronic excitations in two distinct bands, 7f 4 0 2 and 8f 0 0 0, at roughly the same total energy. By analyzing the images, we directly obtain the total translation energy distributions for the two dissociation channels and the branching between them. The results show that there exist differences for competitive dissociation pathways between H and H 2 elimination from C 2H 4 + depending on the vibronic preparation used, i.e., on the vibrational excitation in the ground state of the cation prior to photodissociation. Our findings are discussed in terms of the possible influence of the torsional excitation on competition between direct dissociation, isomerization, and radiationless transitions through conical intersections among the numerous electronic states that participate in the dissociation.

Original languageEnglish
Pages (from-to)7839-7842
Number of pages4
JournalJournal of Physical Chemistry A
Issue number35
StatePublished - 8 Sep 2005


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