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 Title: PREDICTING CORIOLIS VIBRATION-ROTATION COUPLING COEFFICIENTS FOR ANALYSIS OF ROTATIONAL SPECTRA, PART 1: THEORY AND IMPLEMENTATION Author(s): Owen, Andrew N. Contributor(s): McMahon, Robert J.; Woods, R. Claude; Esselman, Brian J. Subject(s): Theory and Computation Abstract: The fitting and assignment of the rotational spectra of Coriolis-coupled distorted rotors is considerably more difficult than for isolated distorted rotors due to the sensitivity of a non-linear least-squares fit to the initial parameters and the lack of \textit{a priori} predictions of the Coriolis coupling coefficients for all but the simplest couplings. Herein, we present our efforts to automatically generate computational predictions of Coriolis coupling coefficients ($G_{\alpha}$, $F_{\beta\gamma}$, and their corresponding centrifugal distortion terms) using the outputs of Gaussian or CFOUR programs. The theory for deriving vibration-rotation couplings (through Van Vleck-style perturbation of the vibration-rotation Hamiltonian) and the formulas necessary for calculating a variety of coupling coefficients ($G_{\alpha}$, $F_{\beta\gamma}$ for $\sum_{i}|\Delta v_{i}|\leq3$ and $G_{\alpha}^{J}$, $G_{\alpha}^{K}$, $F_{\beta\gamma}^{J}$, $F_{\beta\gamma}^{K}$ for $\sum_{i}|\Delta v_{i}| = 2$) have been known for some time, yet only predictions of $G_{\alpha}$ for $\sum_{i}|\Delta v_{i}| = 2$ have been used. Our implementation for predicting coupling coefficients of low order in rotation ($G_{\alpha}$ and $F_{\beta\gamma}$) is straightforward. We found for terms of higher order ($G_{\alpha}^{J}$, $G_{\alpha}^{K}$, $F_{\beta\gamma}^{J}$, $F_{\beta\gamma}^{K}$), however, that it is necessary to carry out reductions of the respective formulas. We therefore adapted the methodology used for reducing the centrifugal distortion to obtain predictions of the coupling coefficients that can be used for \textit{a priori} prediction and for post-fitting comparison directly to those determined experimentally. Issue Date: 22-Jun-20 Publisher: International Symposium on Molecular Spectroscopy Citation Info: APS Genre: CONFERENCE PAPER/PRESENTATION Type: Text Language: English URI: http://hdl.handle.net/2142/107341 Date Available in IDEALS: 2020-06-26
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