Refining Search Methods for Intermediate Velocity Molecular Clouds

We present an analysis of OH 18-cm upper limits toward 11 sightlines at high galactic latitudes using the 305-m radio telescope at the Arecibo Observatory. These results stem from a search for molecular gas in previously unidentified intermediate-velocity clouds that are predicted to have a sufficient molecular content so as to be detected in emission. Such clouds are important for investigating the underlying physics of the atomic-molecular transition of gas in the interstellar medium, and due to their unique dynamics indicative of infalling motion toward the galactic plane, they may also provide insight into mechanisms that supply pristine gas for the galactic star formation cycle. We will discuss the implications of the OH upper limits in the context of diffuse cloud models that, in conjunction with existing HI and dust extinction data, may be useful for constraining more stringent search criteria for this important class of molecular clouds.