Dissociation dynamics and multiphoton ionization mechanism of ammonia clusters

F. Misaizu, P. L. Houston, N. Nishi, H. Shinohara, T. Kondow, M. Kinoshita

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Two-color, two-photon ionization of ammonia has been used to investigate the ionization and dissociation mechanisms of ammonia clusters. By observing the ion signals in a reflectron time-of-flight mass spectrometer as a function of the delay time between the two laser pulses, it is found that the lifetime of the intermediate to formation of (NH3)2H+ and higher mass cluster ions is at least 500 times longer than that to formation of NH4+ and (NH3)2+. Similar results are found for deuterated ammonia. The intermediate is formed by one-photon excitation in the energy range accessing the à 1A2 state of ammonia. This observation confirms that the mechanism of ionization of the dimer in this energy region is two-photon ionization followed by the rapid intracluster proton-transfer reaction (NH3)2+ → NH4+ + NH2. The mechanism for ionization of larger clusters is discussed.

Original languageEnglish
Pages (from-to)7041-7044
Number of pages4
JournalJournal of Physical Chemistry
Issue number20
Publication statusPublished - 1989


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