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

Neutral excited radicals formed by ethylene photodissociation in the 8-24 eV region
Neutral excited radicals formed by ethylene photodissociation in the 8-24 eV region
Dissociation pathways following phololysis 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 (A) 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 H-2 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 all easier relaxation of the excited state into pyramidalised states.
vacuum-ultraviolet photodissociation, dissociation dynamics, rydberg states, rate constants, 157 nm, spectroscopy, acetylene, spectrum, methylene, molecules
1463-9076
2093-2100
Alnama, Koutayba
6d5fad49-4db5-4a80-bb59-e1c867af14f1
Boye, Séverine
74f748f4-3522-4737-bced-a6f6e449ea96
Douin, Stéphane
189b6770-00e1-43c8-9c0b-3b1c897e792f
Innocenti, Fabrizio
2e95973e-c7b9-4166-8bf2-8b06a713fdfa
O'Reilly, John
635e3e20-5fe1-43e5-82eb-775f4b5f9619
Roche, Anne-Lise
17fe97ff-b509-4a8f-96a2-bf7357f50655
Shafizadeh, Niloufar
a37b9d60-cce7-4360-bb76-b3185d39e619
Zuin, Lucia
d81b1d9e-03b3-416c-b9cc-1d0d4f4a621b
Gauyacq, Dolores
c8d92e8b-d28a-4a4b-9d7c-5f48065d1714
Alnama, Koutayba
6d5fad49-4db5-4a80-bb59-e1c867af14f1
Boye, Séverine
74f748f4-3522-4737-bced-a6f6e449ea96
Douin, Stéphane
189b6770-00e1-43c8-9c0b-3b1c897e792f
Innocenti, Fabrizio
2e95973e-c7b9-4166-8bf2-8b06a713fdfa
O'Reilly, John
635e3e20-5fe1-43e5-82eb-775f4b5f9619
Roche, Anne-Lise
17fe97ff-b509-4a8f-96a2-bf7357f50655
Shafizadeh, Niloufar
a37b9d60-cce7-4360-bb76-b3185d39e619
Zuin, Lucia
d81b1d9e-03b3-416c-b9cc-1d0d4f4a621b
Gauyacq, Dolores
c8d92e8b-d28a-4a4b-9d7c-5f48065d1714

Alnama, Koutayba, Boye, Séverine, Douin, Stéphane, Innocenti, Fabrizio, O'Reilly, John, Roche, Anne-Lise, Shafizadeh, Niloufar, Zuin, Lucia and Gauyacq, Dolores (2004) Neutral excited radicals formed by ethylene photodissociation in the 8-24 eV region. Physical Chemistry Chemical Physics, 6 (9), 2093-2100. (doi:10.1039/b316056d).

Record type: Article

Abstract

Dissociation pathways following phololysis 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 (A) 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 H-2 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 all easier relaxation of the excited state into pyramidalised states.

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More information

Published date: 7 May 2004
Keywords: vacuum-ultraviolet photodissociation, dissociation dynamics, rydberg states, rate constants, 157 nm, spectroscopy, acetylene, spectrum, methylene, molecules

Identifiers

Local EPrints ID: 20118
URI: https://eprints.soton.ac.uk/id/eprint/20118
ISSN: 1463-9076
PURE UUID: b43a0cfd-994c-402a-a9fa-00c4a8dbf59e

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Date deposited: 22 Feb 2006
Last modified: 15 Jul 2019 19:26

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Contributors

Author: Koutayba Alnama
Author: Séverine Boye
Author: Stéphane Douin
Author: Fabrizio Innocenti
Author: John O'Reilly
Author: Anne-Lise Roche
Author: Niloufar Shafizadeh
Author: Lucia Zuin
Author: Dolores Gauyacq

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