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Title: Communication: The ground electronic state of Si{sub 2}C: Rovibrational level structure, quantum monodromy, and astrophysical implications

We report the gas-phase optical detection of Si{sub 2}C near 390 nm and the first experimental investigation of the rovibrational structure of its {sup 1}A{sub 1} ground electronic state using mass-resolved and fluorescence spectroscopy and variational calculations performed on a high-level ab initio potential. From this joint study, it is possible to assign all observed K{sub a} = 1 vibrational levels up to 3800 cm{sup −1} with confidence, as well as a number of levels in the K{sub a} = 0, 2,  and 3 manifolds. Dixon-dip plots for the bending coordinate (ν{sub 2}) allow an experimental determination of a barrier to linearity of 783(48) cm{sup −1} (2σ), in good agreement with theory (802(9) cm{sup −1}). The calculated (K{sub a}, ν{sub 2}) eigenvalue lattice shows an archetypal example of quantum monodromy (absence of a globally valid set of quantum numbers) that is reflected by the experimentally observed rovibrational levels. The present study provides a solid foundation for infrared and optical surveys of Si{sub 2}C in astronomical objects, particularly in the photosphere of N- and J-type carbon stars where the isovalent SiC{sub 2} molecule is known to be abundant.
Authors:
; ;  [1] ;  [2] ;  [3] ;  [4]
  1. Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, Massachusetts 02138 (United States)
  2. JILA, National Institute of Standards and Technology and Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States)
  3. Department of Chemistry, University of Colorado, Boulder, Colorado 80309 (United States)
  4. Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712 (United States)
Publication Date:
OSTI Identifier:
22490810
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 23; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ASTROPHYSICS; CARBON STARS; DETECTION; EIGENVALUES; FLUORESCENCE SPECTROSCOPY; MOLECULES; PHOTOSPHERE; SILICON CARBIDES; SOLIDS