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Dissociative double photoionization of benzene molecules in the 26-33 eV energy range

A TOF mass spectrometric study affords the dissociative double dissociation of benzene by UV synchroitron radiation. M. Alagia et al Phys. Chem.Chem. Phys. 13 (2011) 82454


A time-of-flight mass spectrometer with a position sensitive ion detector was used to study the
dissociative double ionization of benzene by UV synchrotron radiation. The threshold energy for
the main dissociative processes, leading to CH3+ + C5H3+, C2H3+ + C4H3+ and C2H2+ + C4H4+
ion pairs were characterized by exploiting a photoelectron-photoion-photoion-coincidence
technique, giving 27.8 ± 0.1, 29.5 ± 0.1, and 30.2 ± 0.1 eV, respectively. The first reaction also
proceeds via the formation of a metastable C6H6
2+ dication. The translational kinetic energy of
the ionic products was evaluated by measuring the position of ions arriving to the detector.
Theoretical calculations of the energy and structure of dissociation product ions were performed
to provide further information on the dynamics of the charge separation reactions following the
photoionization event.
 

By comparison with cytosine spectra, we conclude that the methylation of C5 carbon atoms hardly changes the fraction of hydroxy tautomers but changes significantly the imino–oxo versus amino–oxo tautomeric equilibrium. In 5-methylcytosine, these tautomers are present with nearly the same population, while in the case of cytosine, the concentration of the amino–oxo form was higher by a factor of 2. The substitution of hydrogen by fluorine in the C5 position leads to a strong dominance of the hydroxy tautomer. For isocytosine, the tautomeric amino–oxo and amino–hydroxy forms coexist, with the amino–oxo form less stable by 2.07 kcal/mol at 425 K.

Retrive article

Dissociative double photoionization of benzene molecules in the 26–33 eV energy range
Michele Alagia, Pietro Candori, Stefano Falcinelli, Fernando Pirani, Maria S. Pedrosa Mundim, Robert Richter, Marzio Rosi, Stefano Stranges, Franco Vecchiocattivi
Phys. Chem. Chem. Phys.13 (2011) 8245
doi: 10.1039/c0cp02678f

 

Last Updated on Thursday, 18 October 2018 12:07