  Cosmic ray detectors use air as a radiator for luminescence. In water and
ice, Cherenkov light is the dominant light producing mechanism when the
particle's velocity exceeds the Cherenkov threshold, approximately three
quarters of the speed of light in vacuum. Luminescence is produced by highly
ionizing particles passing through matter due to the electronic excitation of
the surrounding molecules. The observables of luminescence, such as the
wavelength spectrum and decay times, are highly dependent on the properties of
the medium, in particular, temperature and purity. The results for the light
yield of luminescence of previous measurements vary by two orders of magnitude.
It will be shown that even for the lowest measured light yield, luminescence is
an important signature of highly ionizing particles below the Cherenkov
threshold. These could be magnetic monopoles or other massive and highly
ionizing exotic particles. With the highest observed efficiencies, luminescence
may even contribute significantly to the light output of standard model
particles such as the PeV IceCube neutrinos. We present analysis techniques to
use luminescence in neutrino telescopes and discuss experimental setups to
measure the light yield of luminescence for the particular conditions in
neutrino detectors.
