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 Title: Improved Semi-experimental Equilibrium Structure Determination And Theoretical Prediction Of Pyridazine (o-c4h4 Author(s): Owen, Andrew N. Contributor(s): McMahon, Robert J.; Woods, R. Claude; Stanton, John F.; Esselman, Brian J.; Zdanovskaia, Maria Subject(s): Structure determination Abstract: We obtained an improved semi-experimental equilibrium structure ($r_{e}$$^{SE}) of pyridazine (\textit{o}-\chem{C_4H_4N_2}) by improving the distorted-rotor least-squares fits of previously reported experimental data by incorporating fits of four previously unobserved isotopologues and by using higher level, isotopologue-dependent \textit{ab initio} corrections from CCSD(T)/cc-pCVTZ in the r_{e}$$^{SE}$ determination. As a result, we improved the determination of the parameters of pyridazine by a factor of two, obtaining $2\sigma$ uncertainties of less than $0.001$ {\AA} and $0.04^{\circ}$ in the bond distances and angles, respectively. Additionally, we have obtained an improved theoretical prediction of the structure by using a CCSD(T)/cc-pCV5Z optimization and applying corrections to account for extrapolation to the complete basis set limit, for effects of electron correlation, for relativistic effects, and for the Born-Oppenheimer approximation. The resulting theoretical structural parameters are almost all within the corresponding uncertainties of the improved $r_{e}$$^{SE} parameters. Finally, we analyzed the effect of including additional isotopologues on the r_{e}$$^{SE}$ structure and extended the analysis for comparison to the minimal set of isotopologues as used in substitution structure determinations. Issue Date: 2021-06-25 Publisher: International Symposium on Molecular Spectroscopy Genre: Conference Paper / Presentation Type: Text Language: English URI: http://hdl.handle.net/2142/111250 Date Available in IDEALS: 2021-09-24
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