Department of Physics. University of Illinois at Uranba-Champaign Low Temperature Martensitic Transition in a Pu-Ga Alloy Tai C. Chiang Department of Physics. University of Illinois at Uranba-Champaign X-ray thermal diffuse scattering mapping (TDS) of phonons in Pu-Ga: Results show that the L-point soft mode in Pu-Ga does not change as the temperature is lowered toward the transition temperature. This is rather unusual and points to the collective response or instability of the 5f electronic configuration as a likely driving mechanism for the transition. Phonon frequency as a function of temperature for different types of transitions. TDS patterns from a (111) grain and a (110) grain at different temperatures and the corresponding fits.