Research during those early years was dominated by optical spectroscopy. In 1971 an IBM research group produced the first photoelectron spectra using Tantalus, a milestone in the development of photoemission spectroscopy as a research tool. The tunability of the radiation allowed researchers to disentangle a material's ground-state electronic properties. In the mid-1970s the increasing beam current from the ring gave intensity levels sufficient for angle-resolved photoemission spectroscopy, with a joint Bell Labs–Montana State University group conducting the earliest experiments. As an experimental technique, angle-resolved photoemission developed rapidly and had an important conceptual impact on condensed-matter physics. Gas-phase spectroscopy was another successful field at SRC, starting from early absorption studies of noble gases.