Knowledge Bank

Guided by the ab initio predictions for the $OH-$ fundamental made by Lee and Schaefer (1) and by Werner, Rosmus, and Reinsch (2) along with the laser photodetachment results of Schulz et al. (3), we measured the $v1\leftarrow 0$ band of $\mathrm{<mrow\; data-mjx-texclass="ORD">16</mrow>}OH-$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">18</mrow>}OH-$ by velocity modulation spectroscopy with a color center laser (4). The $OH-$ concentration was found to be maximized in a $Ar/H2/O2$ or $Ar/H2/H2O$ discharge where the addition of argon both rotationally heats the $OH-$and increases its overall concentration. The $OH-$ signal was also found to be dramatically dependent on the presence of metal sputtered on the discharge cell wall. The $\mathrm{<mrow\; data-mjx-texclass="ORD">16</mrow>}OH-$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">18</mrow>}OH-$ bands were analyzed separately with a least squares analysis yielding the equilibrium bond length and vibration-rotation constants through sextic distortion terms. Using the band origins of the two isotopomers, the harmonic vibrational frequencies and first order anharmonicities were calculated.