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Title: Reduced dimension rovibrational variational calculations of the S1 state of C2H2. II. The S1 rovibrational manifold and the effects of isomerization

Journal Article · · Journal of Chemical Physics
DOI:https://doi.org/10.1063/1.4859876· OSTI ID:1557648
 [1];  [1];  [2];  [3];  [4]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Univ. of Colorado, Boulder, CO (United States)
  2. Univ. of Texas, Austin, TX (United States)
  3. Academia Sinica, Taipei (Taiwan); Univ. of British Columbia, Vancouver, BC (Canada)
  4. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
+ Show Author Affiliations

Reduced dimension variational calculations have been performed for the rovibrational level structure of the S1 state of acetylene. The state reflects an unusually complicated level structure, for various reasons. First, the potential energy surface has two accessible conformers, trans and cis. The cis conformer lies about 2700 cm–1 above the trans, and the barrier to cis-trans isomerization lies about 5000 cm–1 above the trans minimum. The trans vibrations ν4 (torsion) and ν6 (asym. bend) interact very strongly by Darling-Dennison and Coriolis resonances, such that their combination levels and overtones form polyads with unexpected structures. Both conformers exhibit very large x36 cross-anharmonicity since the pathway to isomerization is a combination of ν6 and ν3 (sym. bend). Near the isomerization barrier, the vibrational levels show an even-odd K-staggering of their rotational levels as a result of quantum mechanical tunneling through the barrier. The current calculations address all of these complications, and reproduce the observed K-structures of the bending and C–C stretching levels with good qualitative accuracy. It is anticipated that they will assist with the assignment of the irregular patterns near the isomerization barrier.

Research Organization:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
FG02-87ER13671
OSTI ID:
1557648
Journal Information:
Journal of Chemical Physics, Vol. 140, Issue 2; ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 8 works
Citation information provided by
Web of Science

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Cited By (2)

Full-dimensional quantum mechanics calculations for the spectroscopic characterization of the isomerization transition states of HOCO/DOCO systems journal January 2018
One-colour (∼220 nm) resonance-enhanced (S 1  − S 0 ) multi-photon dissociation of acetylene: probe of the C 2 A 1 Π u  −  X 1 Σ + g band by frequency-modulation spectroscopy journal February 2020

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