Fragmentation of doubly charged ammonia cations NH
3
++
studied by the photoion-photoion coincidence (PIPICO) method |
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Authors: | D Winkoun G Dujardin |
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Institution: | 1. Laboratoire de Photophysique Moléculaire du CNRS, Université Paris Sud, Orsay, France 2. Laboratoire du CNRS pour l'Utilisation du Rayonnement Electromagnétique, Université Paris Sud, Orsay, France
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Abstract: | Doubly charged NH 3 ++ cations were produced by double photoionization of neutral ammonia molecules by using the synchrotron radiation from ACO as a photon source of variable energy in the 35–49 eV energy range. The fragmentation of NH 3 ++ was studied by the photoion-photoion coincidence (PIPICO) method. NH 3 ++ cations were produced in the \(\tilde X^1 \) A 1 and \(\tilde B^1 \) electronic states of which the onset energies were measured at, respectively, 35.4±0.5 eV and 44.5±0.5 eV. It was shown that the NH 3 ++ ions, initially produced in their \(\tilde X^1 \) A 1 state, rapidly dissociate (in less than 50 ns), into NH 2 + + H+. Furthermore, the comparison with results obtained by other methods indicates that NH 3 ++ ions can either be long-lived (τ>10 µs) or slowly dissociating (1 µs<τ<10 µs) or rapidly dissociating (τ<50 ns), depending on their geometry and/or internal energy in their \(\tilde X^1 \) E A 1 electronic state. |
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