This award will support a survey of low frequency spectral lines from the southern portion of the plane of our Galaxy. The lines are produced by the recombination of ionized carbon atoms into very high quantum states with principal quantum numbers between 272 and 768; the corresponding frequencies of the lines are 325 MHz to 14.5 MHz. The atoms producing these lines are extremely large and fragile with diameters up to 50 microns. Such atoms can exist only under the benign conditions found in cool interstellar clouds, and they are extremely sensitive to their environment. For this reason they are excellent diagnostics of temperature, pressure, and ionization levels in cool interstellar clouds. All previous observations have been made with northern hemisphere telescopes. This survey will cover the southern portion of the galactic plane and the Magellanic Clouds using the Parkes telescope in Australia in order to discover more line emitting regions.
