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Issue 9, 2004
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Neutral excited radicals formed by ethylene photodissociation in the 8–24 eV region

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Dissociation pathways following photolysis of ethylene C2H4 in the 6.2–24.8 eV energy range, and leading to excited fragment production are investigated. The dispersed visible fluorescence of the products has been recorded for a large range of excitation energies, allowing for the determination of experimental energy thresholds for the different pathways. It is found that the C2H (Ã) radical is the dominant fragment, emitting in the visible range. It is formed with a considerable amount of vibrational excitation energy, as was previously reported in the photodissociation study of acetylene C2H2. From the dissociation threshold measurements, several barrierless processes are evidenced. In particular, the excited CH* (A or B) radical is formed via an intermediate isomer, ethylidene, with no excess energy. More surprisingly, all channels involving one H2 molecular elimination are observed without any barrier, unlike the dissociation processes occurring on the ground state potential energy surface (PES) of C2H4. Most probably, this observation originates from an easier relaxation of the excited state into pyramidalised states.

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Publication details

The article was received on 09 Dec 2003, accepted on 04 Feb 2004 and first published on 02 Mar 2004

Article type: Paper
DOI: 10.1039/B316056D
Phys. Chem. Chem. Phys., 2004,6, 2093-2100

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    Neutral excited radicals formed by ethylene photodissociation in the 8–24 eV region

    K. Alnama, S. Boyé, S. Douin, F. Innocenti, J. O'Reilly, A. Roche, N. Shafizadeh, L. Zuin and D. Gauyacq, Phys. Chem. Chem. Phys., 2004, 6, 2093
    DOI: 10.1039/B316056D

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