Rotational Spectroscopy and Partial Semi-Experimental Equilibrium (reSE) and Substitution (rsSE) Structures of Cyclobutenone (c-C4H4O).
- 1Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin53706, United States.
- 2Department of Chemistry and Biochemistry, Kent State University, Kent, Ohio44240, United States.
- 3Quantum Theory Project, Departments of Physics and Chemistry, University of Florida, Gainesville, Florida32611, United States.
Abstract
Partial semi-experimental equilibrium (reSE) and substitution (rsSE) structures of cyclobutenone (c-C4H4O, Cs, μa = 3.4 D) have been determined for the first time via rotational spectroscopy. The rotational spectrum of this reactive species, which contains a highly strained four-membered ring, has been measured from 9 to 735 GHz. Over 3800 transitions for the ground vibrational state of the normal isotopologue of cyclobutenone were measured, assigned, and least-squares fit to sextic distorted-rotor A- and S-reduced Hamiltonians in the Ir representation, providing a complete set of quartic and sextic centrifugal distortion parameters. Rotational transitions for each of the singly substituted heavy-atom isotopologues were measured at natural abundance. Rotational constants (B0) for the six isotopologues were converted to equilibrium values (Be) using CCSD(T)/cc-pCVTZ vibration-rotation interaction and electron-mass corrections, enabling the determination of partial reSE and rsSE structures that define all of the heavy-atom parameters of cyclobutenone. The two different sets of semi-experimental structural parameters (reSE and rsSE) are compared to the "best theoretical estimate" (BTE re) values, which are derived from the CCSD(T)/cc-pCV5Z re structure with additional corrections addressing finite basis set, higher-level electron correlation, and relativistic effects, as well as incorporating the diagonal Born-Oppenheimer correction. Additionally, transitions of the four lowest-energy vibrationally excited states have been assigned, measured, and least-squares fit to A-reduced, sextic centrifugally distorted-rotor Hamiltonians in the Ir representation. While ν21 was well-modeled using a single-state Hamiltonian, 2ν21, ν14, and ν20 form an anharmonic- and Coriolis-coupled triad and were treated by a three-state Hamiltonian model.
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BibTeX
@article{esselman2026rotational,
title = {{Rotational Spectroscopy and Partial Semi-Experimental Equilibrium (reSE) and Substitution (rsSE) Structures of Cyclobutenone (c-C4H4O).}},
author = {Brian J Esselman and Michael J Carrillo and Madeleine G Atwood and Nitai P Sahoo and Zoe K Deems and Michael J Tubergen and Maria A Zdanovskaia and R Claude Woods and Robert J McMahon},
journal = {The journal of physical chemistry. A},
year = {2026},
month = oct,
doi = {10.1021/acs.jpca.6c04937},
url = {https://europepmc.org/article/MED/42917613},
note = {CC BY},
}
RIS
TY - JOUR
TI - Rotational Spectroscopy and Partial Semi-Experimental Equilibrium (reSE) and Substitution (rsSE) Structures of Cyclobutenone (c-C4H4O).
AU - Brian J Esselman
AU - Michael J Carrillo
AU - Madeleine G Atwood
AU - Nitai P Sahoo
AU - Zoe K Deems
AU - Michael J Tubergen
AU - Maria A Zdanovskaia
AU - R Claude Woods
AU - Robert J McMahon
PY - 2026
DA - 2026/10/01
JO - The journal of physical chemistry. A
DO - 10.1021/acs.jpca.6c04937
UR - https://europepmc.org/article/MED/42917613
AB - Partial semi-experimental equilibrium (reSE) and substitution (rsSE) structures of cyclobutenone (c-C4H4O, Cs, μa = 3.4 D) have been determined for the first time via rotational spectroscopy. The rotational spectrum of this reactive species, which contains a highly strained four-membered ring, has been measured from 9 to 735 GHz. Over 3800 transitions for the ground vibrational state of the normal isotopologue of cyclobutenone were measured, assigned, and least-squares fit to sextic distorted-rotor A- and S-reduced Hamiltonians in the Ir representation, providing a complete set of quartic and sextic centrifugal distortion parameters. Rotational transitions for each of the singly substituted heavy-atom isotopologues were measured at natural abundance. Rotational constants (B0) for the six isotopologues were converted to equilibrium values (Be) using CCSD(T)/cc-pCVTZ vibration-rotation interaction and electron-mass corrections, enabling the determination of partial reSE and rsSE structures that define all of the heavy-atom parameters of cyclobutenone. The two different sets of semi-experimental structural parameters (reSE and rsSE) are compared to the "best theoretical estimate" (BTE re) values, which are derived from the CCSD(T)/cc-pCV5Z re structure with additional corrections addressing finite basis set, higher-level electron correlation, and relativistic effects, as well as incorporating the diagonal Born-Oppenheimer correction. Additionally, transitions of the four lowest-energy vibrationally excited states have been assigned, measured, and least-squares fit to A-reduced, sextic centrifugally distorted-rotor Hamiltonians in the Ir representation. While ν21 was well-modeled using a single-state Hamiltonian, 2ν21, ν14, and ν20 form an anharmonic- and Coriolis-coupled triad and were treated by a three-state Hamiltonian model.
SN - 1089-5639
SN - 1520-5215
ER -