Experimental limits on deviations fromZ2dependence of Čerenkov radiation by heavy ions

We have exposed a variety of Čerenkov radiators to relativistic Ne, Ar, and Fe ions at the Lawrence Berkeley Laboratory's Bevalac and have examined the charge dependence of the Čerenkov emission. Classically, and to first order in relativistic quantum theory, the dependence is $Z^2$, although certain higherorder corrections suggest a $Z^4$ dependence as well. Our experimental results are consistent with a pure $Z^2$ dependence and limits are placed on $Z^3$ and $Z^4$ higher-order contributions to Čerenkov emission, whose theoretical bases are briefly discussed. In addition to primary Čerenkov emission, we discuss light sources such as Čerenkov emission by secondary electrons, saturated radiator scintillation, and others which are confronted in most experimental configurations incorporating Čerenkov radiators.