  We report the first results from the GammeV search for chameleon particles,
which may be created via photon-photon interactions within a strong magnetic
field. Chameleons are hypothesized scalar fields that could explain the dark
energy problem. We implement a novel technique to create and trap the
reflective particles within a jar and to detect them later via their afterglow
as they slowly convert back into photons. These measurements provide the first
experimental constraints on the couplings of chameleons to photons.
