Search for Anomalous Photonic Events with Missing Energy in                    
e+e- Collisions at sqrt(s) = 130, 136 and 183 GeV                              
  
Photonic events with large missing energy have been observed in                
e+e- collisions at a centre-of-mass energy of 130, 136 and 183 GeV             
using the OPAL detector at LEP. Results are presented for event                
topologies consistent with a single photon or with an acoplanar                
photon pair.                                                                   
Cross-section measurements are performed within the kinematic acceptance       
of each selection.                                                             
These results are compared with the expectations from                          
the Standard Model. No evidence is                                             
observed for new physics contributions to these final states.                  
Upper limits on the cross-sections for the production of                       
XY and XX final states, followed by the decay X to Y gamma,                    
are derived for the case of stable and invisible Y.                            
These limits apply to                                                          
single and pair production of excited neutrinos,                               
to neutralino production and to                                                
supersymmetric models with a light gravitino.                                  
  
 Parallel session :11                  
 Plenary  session :7a