 At Rutgers she has been a major member of the nuclear physics research group working on the tandem Van de Graaff accelerator, as well as a condensed-matter physicist, performing experiments using the Mössbauer effect, by which she investigated the electronic structure of magnetic materials.According to the 'Contributions of 20th Century Women to Physics' (CWP) Project of the UCLA entry on Koller, Koller was a pioneer in several areas of nuclear and condensed matter physics, including the first identification of the double gamma decay of the observationally stable but theoretically unstable 40Ca isotope to the ground state