High-resolution laser excitation spectra of the S-1 <-- S-0 O-0(0) bands of the 1:1 van der Waals complexes of 4-fluorostyrene with atoms of argon and neon are presented. The rotational structure of each is fully assigned using a rigid asymmetric rotor Hamiltonian. The rotational constants for the complexes are used to extract effective coordinates for the rare-gas atoms which contain both dynamic and geometric information. Semiempirical potentials for the clusters in the ground and excited states are determined by fitting to the rotational constants and vibrational frequencies from three-dimensional quantum calculations to the experimental data. The effective coordinates are interpreted by comparison with the results of these quantum calculations on the potential surfaces obtained.