Photoreaction of benzophenone (BP) in various BP/solvent molecule clusters was investigated in the jet. Solvent molecules examined were aromatic compounds, amines, and 1,4-cyclohexadiene (CHD). A broad band emission was observed for clusters and the peak wavelength depends on the ionization potential of solvent, showing that these emissions were from exciplexes. A dual emission band was observed in BP/CHD clusters: One was from BP ketyl and the other from the exciplex. The intensity ratio of these emissions depends on the condition of the jet, which suggests the branching ratio of intracluster photoreactions depends on the nature of BP/CHD clusters. (C) 2002 Elsevier Science B.V. All rights reserved.