Near infrared overtone (vOH = 2 ← 0) spectroscopy of Ne–H2O clusters
Abstract
Vibrationally state selective overtone spectroscopy and dynamics of weakly bound Ne–H2O complexes (D0(para) = 31.67 cm−1, D0(ortho) = 34.66 cm−1) are reported for the first time, based on near infrared excitation of van der Waals cluster bands correlating with vOH = 2 ← 0 overtone transitions (|02−⟩←|00+⟩ and |02+⟩←|00+⟩) 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 ab initio potential energy surface (CCSD(T)/VnZ-f12 (n = 3,4), corrected for basis set superposition error and extrapolated to the complete basis set limit) are employed for assignment of Σ←Σ,Π←Σ, and Σ←Π infrared bands in the overtone spectra, where Σ(K = 0) and Π (K = 1) represent approximate projections (K) of the body angular momentum along the Ne–H2O internuclear axis. End-over-end tumbling of the ortho Ne–H2O cluster is evident via rotational band contours observed, with band origins and rotational progressions in excellent agreement with ab initio frequency and intensity predictions. A clear Q branch in the corresponding |02+⟩fΠ(111)←eΣ(000) para Ne–H2O spectrum provides evidence for a novel e/f parity-dependent metastability in these weakly bound clusters, in agreement with ab initio bound state calculations and attributable to the symmetry blocking of an energetically allowed channel for internal rotor predissociation. Finally, Boltzmann analysis of the rotational spectra reveals anomalously low jet temperatures (Trot ≈ 4(1) K), which are attributed to “evaporative cooling” of weakly bound Ne–H2O clusters and provide support for similar cooling dynamics in rare gas-tagging studies.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Mar 14, 2017
- Source ID
- 10.1063/1.4977061
Entities
People
- Ad van der Avoird
- Christian Pluetzer
- David J. Nesbitt
- Jérôme Loreau
- Michael P. Ziemkiewicz
- Michael Wojcik
Organizations
- Air Force Office of Scientific Research
- Alexander von Humboldt Foundation
- Radboud University Nijmegen
- United States Department of Energy
- University of Colorado
- Université Libre de Bruxelles