We studied fluorescence excitation and resonant two-photon ionization of jet-cooled fluorene clusters formed in pulsed supersonic expansion of He. We also elucidated the molecular structures and energies of the dimer by using the Mϕller-Plesset correlation energy correction truncated at secondorder (MP2) and the density-functional theory (DFT) methods. The 0 0 0 band of the dimer was found to be 33574 cm−1, lower than that of the monomer by 217 cm−1. The R2PI spectrum of the dimer mimics that of the monomer, indicating that the clustering does not significantly affect the vibronic peak positions and intensities. The MP2 calculation indicates that there are at least five conformers in the dimer and that a partially overlapped conformer having a C 2 symmetry is lowest in energy.