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VUV fragmentation of some hydrofluorocarbon cations studied using coincidence techniques

Lookup NU author(s): Dr Dominic Paul Seccombe

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Abstract

Threshold photoelectron-photoion coincidence (TPEPICO) spectroscopy has been used to investigate the decay dynamics of the valence electronic states of the parent cation of several hydrofluorocarbons (HFC), based on fluorine-substituted ethane, in the energy range 11-25 eV. We present data for CF3CHF2, CF3-CH2F, CF3-CH3 and CHF2-CH3. The threshold photoelectron spectra (TPES) of these molecules show a common feature of a broad, relatively weak ground state, associated with electron removal from the highest-occupied molecular orbital (HOMO) having mainly C-C σ-bonding character. Adiabatic and vertical ionisation energies for the HOMO of the four HFCs are presented, together with corresponding values from ab initio calculations. For those lower-energy molecular orbitals associated with non-bonding fluorine 2pπ lone pair electrons, these electronic states of the HFC cation decay impulsively by C-F bond fission with considerable release of translational kinetic energy. Appearance energies are presented for formation of the daughter cation formed by such a process (e.g. CF3-CHF+), together with ab initio energies of the corresponding dissociation channel (e,g. CF3-CHF+ + F). Values for the translational kinetic energy released are compared with the predictions of a pure-impulsive model.

Publication metadata

Author(s): Zhou W, Seccombe DP, Chim RYL, Tuckett RP

Publication type: Article

Publication status: Published

Journal: Surface Review and Letters

Year: 2002

Volume: 9

Issue: 1

Pages: 153-158

ISSN (print): 0218-625X

ISSN (electronic):

Publisher: World Scientific Publishing Co. Pte. Ltd.

URL: http://dx.doi.org/10.1142/S0218625X0200204X

DOI: 10.1142/S0218625X0200204X

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