Laser excitation of Th-229 nucleus

A research team led by Prof. Thorsten Schumm from TU Wien and PTB has found the long-sought thorium transition and determined its energy. This achievement combines classical quantum physics and nuclear physics for the first time. Thorium-containing crystals were crucial for this success. The thorium transition's energy was previously unknown, making it difficult to detect. Researchers used lasers to switch an atomic nucleus from one state to another, which is usually challenging due to the high energy required. Thorium-229 is a special nucleus with two closely adjacent energy states. The team developed thorium-containing crystals, enabling the study of large numbers of thorium nuclei, increasing the likelihood of finding the energy transition. Potential applications include the development of an atomic nucleus clock and high-precision measurements of time, gravity, and fundamental physical constants.