What Microwave Astronomical Spectroscopy can tell you about the Carriers of the DIBs

Astronomical microwave spectroscopy has greatly broadened the inventory of identifiable chemical species in diffuse molecular gas and is an increasingly effective way to measure the abundances of polar molecules that may be candidate diffuse interstellar band carriers. Here we review some recent developments that hold new promise for chemical abundance determinations. We summarize and categorize the molecular inventory that has accrued in the past twenty years from microwave observations of diffuse clouds and we present summary tables of the molecular abundances within various chemical families in both dark and diffuse molecular gas.