  We report results from tests of $^{83}$Kr$^{\mathrm{m}}$, as a calibration
source in liquid argon and liquid neon. $^{83}$Kr$^{\mathrm{m}}$ atoms are
produced in the decay of $^{83}$Rb, and a clear $^{83}$Kr$^{\mathrm{m}}$
scintillation peak at 41.5 keV appears in both liquids when filling our
detector through a piece of zeolite coated with $^{83}$Rb. Based on this
scintillation peak, we observe 6.0 photoelectrons/keV in liquid argon with a
resolution of 6% ($\sigma$/E) and 3.0 photoelectrons/keV in liquid neon with a
resolution of 19% ($\sigma$/E). The observed peak intensity subsequently decays
with the $^{83}$Kr$^{\mathrm{m}}$ half-life after stopping the fill, and we
find evidence that the spatial location of $^{83}$Kr$^{\mathrm{m}}$ atoms in
the chamber can be resolved. $^{83}$Kr$^{\mathrm{m}}$ will be a useful
calibration source for liquid argon and neon dark matter and solar neutrino
detectors.
