Knowledge Bank

We report a harmonic frequency $\omega 2=842.464cm-1$, an anharmonic constant, $x22=-3.15cm-1$ and a vibrational angular momentum splitting constant $g22=3.22cm-1$ for the ground state $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma +$ for $HCO+$. The constants are calculated based on experimentally measured Rydberg Series from the $3p\pi$ electronic state which converge to the rovibrational thresholds of the cation $(0000),(0110),(0200)$ and $(0220)$. Along with these thresholds, we use the experimentally measured $x23$ anharmonic constant from Oka et al. and the theoretical $x12$ anharmonic constant from Puzzarini et al. and Lee et al. To further characterize the bending coordinate anharmonicity of the potential energy surface of $HCO+$, we assign Rydberg series obtained from the $3p\pi \mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi (030)\Sigma -N\prime =0$ and 2 converging to rovibrational thresholds $(0310)$ and $(0330)$ in the cation. From this extrapolation, we refine our anharmonic constants for the ground electronic state for $HCO-$.