Radio Recombination Lines (RRL) are a sensitive probe of the properties of the diffuse interstellar medium (ne<10 cm3) in our Galaxy. Together with free-free emission observations, important constraints have been placed on the physical properties and ionization of this gas. It has been inferred that Diffused Ionised Gas (DIG) absorbs more than 70% of the radiation from OB stars in the Galaxy (McKee & Williams 1997). However, we still do not know how the photons from OB stars travel such long distances beyond the ‘classical’ HII regions to ionize this medium (Heiles 1996, Roshi et al. 2011). A detailed study of the morphology of the DIG will help answer this question and test various morphological models (e.g. HII envelopes) that have been proposed. The lower and higher frequency bands of MWA, and its excellent short spacing coverage are ideal for such a study.
Most recently 10 KHz resolution observations of the Galactic Centre had been undertaken with MWA. This project will reduce and analise the data aiming at mapping carbon RRLs in absorbtion and carbon and hydrogen RRLs in emission toward the Galactic Centre at the detail that had never been done before.