Stabilities of nanohydrated thymine radical cations: insights from multiphoton ionization experiments and ab initio calculations*
1 School of Physical Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
2 CIMAP, UMR 6252 (CEA/CNRS/ENSICAEN/Université de Caen Normandie), Caen, France
3 Laboratório de Colisões Atómicas e Moleculares, CEFITEC, Departamento de Física, FCT – Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
Received: 30 December 2016
Received in final form: 21 April 2017
Published online: 11 July 2017
Multi-photon ionization experiments have been carried out on thymine-water clusters in the gas phase. Metastable H2O loss from T+(H2O)n was observed at n ≥ 3 only. Ab initio quantum-chemical calculations of a large range of optimized T+(H2O)n conformers have been performed up to n = 4, enabling binding energies of water to be derived. These decrease smoothly with n, consistent with the general trend of increasing metastable H2O loss in the experimental data. The lowest-energy conformers of T+(H2O)3 and T+(H2O)4 feature intermolecular bonding via charge-dipole interactions, in contrast with the purely hydrogen-bonded neutrals. We found no evidence for a closed hydration shell at n = 4, also contrasting with studies of neutral clusters.
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