Communication: Evidence for dipole-bound excited states in gas-phase I- · MI (M = Na, K, Cs) anionic salt microclusters

Andrew J A Harvey, Naruo Yoshikawa, Jin Guo Wang, Caroline E H Dessent*

*Corresponding author for this work

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We report the first UV laser photodissociation spectra of gas-phase I- · MI (M = Na, K, Cs) alkali halide anionic microclusters. The photodepletion spectra of these clusters display strong absorption bands just below the calculated vertical detachment energies, indicative of the presence of dipole-bound excited states. Photoexcitation at the peak of the transition to the dipole-bound excited state results in production of a primary [MI]- photofragment along with a less intense I- ion. The photofragmentation mechanism of the excited state cluster is discussed in the context of an initial dipole-bound excited state that subsequently relaxes via a vibrational Feschbach resonance. The experiments described have been performed in an electrospray source laser-interfaced quadrupole ion-trap instrument and demonstrated for the first time that dipole-bound excited states can be identified in the relatively high-collision environment of a quadrupole ion-trap, in particular for systems with large dipole moments associated with the presence of charge separation. This indicates considerable potential for future experiments that identify dipole-bound excited states as a "low-resolution" structural probe of biomolecules and molecular charge separation using the instrumentation employed in this work.

Original languageEnglish
Article number101103
JournalJournal of Chemical Physics
Issue number10
Publication statusPublished - 14 Sept 2015

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