Very low speeds of light of a few m/s have recently been demonstrated in highly dispersive media. Remarkable effects can be observed if such a medium is moving and its velocity approaches or even exceeds the speed of light in the medium. A particular example of this kind is the propagation of x-rays in a medium that contains Mossbauer nuclei, with the x-ray energy tuned to the nuclear resonance. When the medium rotates sufficiently fast, the x-rays are deflected so that the time evolution of the nuclear decay is mapped to an angular scale. This effect was called the 'Nuclear Lighthouse Effect'. It opens interesting perspectives for nuclear resonant spectroscopies at modern synchrotron radiation sources. A number of experiments and future applications will be discussed.

ANL Physics Division Colloquium Schedule