Faint Branches in the OH Bands

Intense photographs of the OH bands in the near ultraviolet reveal a number of weak branches of the ${}_{}{}^o{}_{}{}^{}P$ and ${}_{}{}^s{}_{}{}^{}R$ types. The identification of these branches is made by a comparison of the observed wave numbers of the faint lines with their calculated wave numbers. No lines due to the molecule ${\mathrm{O}}^{18}$H were found, although under the conditions of the experiment they were to be expected.