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The gas-phase rotational spectrum from 8 to 750 GHz and the high-resolution infrared (IR) spectrum of pyridazine (o-C4H4N2) have been analyzed for the ground and four lowest-energy vibrationally excited states. A combined global fit of the rotational and IR data has been obtained using a sextic, centrifugally distorted-rotor Hamiltonian with Coriolis coupling between appropriate states. Coriolis coupling has been addressed in the two lowest-energy coupled dyads (ν16, ν13 and ν24, ν9). Utilizing the Coriolis coupling between the vibrational states of each dyad and the analysis of the IR spectrum for ν16 and ν9, we have determined precise band origins for each of these fundamental states: ν16 (B1) = 361.213 292 7 (17) cm−1, ν13 (A2) = 361.284 082 4 (17) cm−1, ν24 (B2) = 618.969 096 (26) cm−1, and ν9 (A1) = 664.723 378 4 (27) cm−1. Notably, the energy separation in the ν16-ν13 Coriolis-coupled dyad is one of the smallest spectroscopically measured energy separations between vibrational states: 2122.222 (72) MHz or 0.070 789 7 (24) cm−1. Despite ν13 being IR inactive and ν24 having an impractically low-intensity IR intensity, the band origins of all four vibrational states were measured, showcasing the power of combining the data provided by millimeter-wave and high-resolution IR spectra. Additionally, the spectra of pyridazine-dx isotopologues generated for a previous semi-experimental equilibrium structure (reSE) determination allowed us to analyze the two lowest-energy vibrational states of pyridazine for all nine pyridazine-dx isotopologues. Coriolis-coupling terms have been measured for analogous vibrational states across seven isotopologues, both enabling their comparison and providing a new benchmark for computational chemistry.
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This content will become publicly available on June 1, 2026
Deperturbation analysis of an avoided crossing in the A1 v = 0 and B1 v = 0 states of WO
The (0,0) and (0,1) bands of the A1 – X0+ and B1 – X0+ transitions of tungsten monoxide (WO) have been recorded in high resolution using intracavity laser absorption spectroscopy techniques (ILS and ILS-FTS). Lines for all four abundant isotopologues, 182WO, 183WO, 184WO, and 186WO, are observed and have been rotationally analyzed and fit using a constrained-variables approach in PGOPHER. While these transitions have been previously described in the literature, this new analysis incorporates all four isotopologues and presents evidence for an avoided crossing interaction between the v = 0 vibrational levels of the A1 and B1 states. New values for spectroscopic constants that incorporate the perturbation interactions are presented and compared to literature results.
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- Award ID(s):
- 1955773
- PAR ID:
- 10633218
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Journal of Molecular Spectroscopy
- Volume:
- 410
- Issue:
- C
- ISSN:
- 0022-2852
- Page Range / eLocation ID:
- 112022
- Subject(s) / Keyword(s):
- Electronic spectra of WO Perturbation analysis WO isotopologues Constrain definitions in PGOPHER Intracavity laser spectroscopy.
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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