HCl, DCl and TCl diatomic molecules in their ground state: predicting Born-Oppenheimer rovibrational spectra

TL;DR

This paper constructs highly accurate Born-Oppenheimer potential curves for HCl, DCl, and TCl molecules, predicting their rovibrational spectra and identifying many states not yet observed experimentally.

Contribution

It provides a comprehensive analytic potential curve for the ground state of HCl, DCl, and TCl, and predicts extensive rovibrational spectra including many states near dissociation.

Findings

Predicted 836, 1625, and 2366 rovibrational bound states for HCl, DCl, TCl respectively.

Identified a large number of weakly-bound states close to dissociation.

Indicated insufficiency of experimental data and predicted missing rovibrational states.

Abstract

The analytic Born-Oppenheimer (B-O) potential curve for the ground state $X^1\Sigma^+$ of the molecule (H,D,T)Cl is constructed for the whole range of internuclear distances $R \in [0,\infty)$ with an accuracy of 3-5 figures in comparison with the RKR-style potential curve derived from available experimental data on vibrational energies. With an accuracy of 3-4 significant figures in the energies, it is predicted for HCl (DCl, TCl) the 836 (1625, 2366) B-O rovibrational bound states with maximal vibrational number $\nu_{max} = 20\, (29, 35)$ and maximal angular momentum $L_{max} = 64\, (90, 109)$ including 24 (46, 63) weakly-bound states (close to the dissociation limit) with energies $\lesssim 10^{-4}$ Hartree. Insufficiency of existing experimental data is indicated and a prediction of the bulk of missing rovibrational states is made for all HCl, DCl, TCl molecules.