1. Nuclear spin/parity dependent spectroscopy and predissociation dynamics in vOH = 2 → 0 overtone excited Ne-H2O clusters: Theory and experiment.
- Author
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Ziemkiewicz, Michael P., Pluetzer, Christian, Loreau, Jérôme, van der Avoird, Ad, and Nesbitt, David J.
- Subjects
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MOLECULAR clusters , *EXCITED states , *NUCLEAR spin , *PARITY (Physics) , *MOLECULAR vibration , *PREDISSOCIATION (Chemistry) , *QUANTUM theory , *NEON - Abstract
Vibrationally state selective overtone spectroscopy and state- and nuclear spin-dependent predissociation dynamics of weakly bound ortho- and para-Ne-H2O complexes (D0(ortho) = 34.66 cm-1 and D0(para) = 31.67 cm-1) are reported, based on near-infrared excitation of van derWaals cluster bands correlating with vOH = 2 ← 0 overtone transitions (|02-≻ and |02+≻) out of the ortho (101) and para (000) internal rotor states of the H2O moiety. Quantum theoretical calculations for nuclear motion on a high level potential energy surface [CCSD(T)/VnZf12 (n = 3, 4)], corrected for basis set superposition error and extrapolated to the complete basis set (CBS) limit, are employed to successfully predict and assign π-Σ, Σ-Σ, and Σ-π infrared bands in the spectra, where Σ Σor Π represent approximate projections of the body-fixed H2O angular momentum along the Ne-H2O internuclear axis. IR-UV pump-probe experimental capabilities permit real-time measurements of the vibrational predissociation dynamics, which indicate facile intramolecular vibrational energy transfer from the H2O vOH = 2 overtone vibrations into the VdWs (van der Waals) dissociation coordinate on the τprediss= 15-25 ns time scale. Whereas all predicted strong transitions in the ortho-Ne-H2O complexes are readily detected and assigned, vibrationally mediated photolysis spectra for the corresponding para-Ne-H2O bands are surprisingly absent despite ab initio predictions of Q-branch intensities with S/N > 20-40. Such behavior signals the presence of highly selective nuclear spin ortho-para predissociation dynamics in the upper state, for which we offer a simple mechanism based on Ne-atom mediated intramolecular vibrational relaxation in the H2O subunit (i.e., |02±≻ → f|01±≻} v2 = 2g), which is confirmed by the ab initio energy level predictions and the nascent OH rotational (N), spin orbit (Π1/2,3/2), and lambda doublet product distributions. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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