  The process e+e- to 2 (or 3) gammas is studied using data recorded with the
OPAL detector at LEP. The data sample taken at a centre-of-mass energy of 189
GeV corresponds to a total integrated luminosity of 178 pb-1. The measured
cross-section agrees well with the expectation from QED. A fit to the angular
distribution is used to obtain improved limits at 95% CL on the QED cut-off
parameters: Lambda+ > 304 GeV and Lambda- > 295 GeV as well as a mass limit for
an excited electron, Me* > 306 GeV assuming equal e*egamma and eegamma
couplings. Graviton exchange in the context of theories with higher dimensions
is excluded for scales G+ < 660 GeV and G- < 634 GeV. No evidence for resonance
production is found in the invariant mass spectrum of photon pairs. Limits are
obtained for the cross-section times branching ratio for a resonance decaying
into two photons and produced in association with another photon.
