Resonant two-photon ionization (R2PI) spectra of the van der Waals (vdW) complexes 1,2-difluorobenzene ... Ar (o-DFB ... Ar) and 1,3-difluorobenzene .... Ar (m-DFB Ar) through the S-1 --> S-0 transition revealed a number of bands near the origin O-0(0). All these bands are assigned to the low-frequency intermolecular vibrations. Quantum calculations using the method of linear-combination of three-dimensional harmonic oscillator products (LCHOP) were carried out to derive the intermolecular vibrational energy levels. Detailed assignments of the intermolecular vibrational modes are accomplished with the help of the quantum calculations and the comparison with the available data on related systems, e.g., C6H6 ... Ar and p-DFB ... Ar. Fluorescence excitation method was used to derive the spectral shifts of intramolecular bands (S-1 <-- S-0) of o, m-DFB upon complexation with Ar. (C) 1997 American Institute of Physics.