Subluminal čerenkov radiation
DOI: 10.1063/1.4796292
In vacuum, nothing travels faster than light. In transparent substances like water, however, it is possible for high-energy charged particles to exceed the speed of a light beam in that substance. When this happens, the particle will radiate a cone of light called Cerenkov radiation. A team of researchers (University of Michigan and Max Planck Institute for Condensed Matter Research in Stuttgart) has now taken a closer look at the theory, and found that conical Cerenkov emission also occurs at subluminal speeds. The researchers verified the finding experimentally using subpicosecond laser pulses to generate—through a nonlinear optical process—relativistic dipoles that emitted infrared Cerenkov radiation in a zinc selenide crystal. (T. E. Stevens et al., Science 291 , 627, 2001 http://dx.doi.org/10.1126/science.291.5504.627 .)
