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Issue 26, 2019
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Energetics and ionization dynamics of two diarylketone molecules: benzophenone and fluorenone

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Abstract

Single photon ionization and subsequent unimolecular ion decomposition were studied on jet-cooled benzophenone and fluorenone separately, using VUV synchrotron radiation in a photoion/photoelectron coincidence setup. Slow PhotoElectron Spectra (SPES) were recorded in coincidence with either the parent or the fragment ions for < 12.5 eV. Dissociative ionization is observed for benzophenone only. The full interpretation of the measurements, including the identification of the neutral and ionic species when dissociative ionization is at play, benefits from high level ab initio computations for determining the equilibrium structures and the energetics of the neutral and ionized molecules and of their fragments. Electronically excited states of the parent molecular ions were calculated also. From this analysis, an accurate experimental determination of the energetics of the benzophenone and fluorenone ions and of their fragmentation channels is available: adiabatic ionization energies of benzophenone at 8.923 ± 0.005 eV and of fluorenone at 8.356 ± 0.007 eV; and appearance energies of benzophenone fragment ions at 11.04 ± 0.02 eV (loss of C6H5), 11.28 ± 0.02 eV (loss of H) and 11.45 ± 0.02 eV (loss of CO). The corresponding fragmentation mechanisms are explored, showing likely concerted bonds rearrangement. Possible pre-ionizing fragmentation is discussed in light of the spectra presented. The structural rigidity of fluorenone diarylketone seems to be the origin of the inhibition of the fragmentation of its cation.

Graphical abstract: Energetics and ionization dynamics of two diarylketone molecules: benzophenone and fluorenone

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Publication details

The article was received on 26 Apr 2019, accepted on 06 Jun 2019 and first published on 06 Jun 2019


Article type: Paper
DOI: 10.1039/C9CP02385B
Phys. Chem. Chem. Phys., 2019,21, 14453-14464

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    Energetics and ionization dynamics of two diarylketone molecules: benzophenone and fluorenone

    Z. Gouid, A. Röder, B. K. Cunha de Miranda, M. Gaveau, M. Briant, B. Soep, J. Mestdagh, M. Hochlaf and L. Poisson, Phys. Chem. Chem. Phys., 2019, 21, 14453
    DOI: 10.1039/C9CP02385B

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