Molecular dynamics simulations were performed for van der Waals clusters naphthalene . Ar(n), n = 1 to 4. For all isomers and conformers of these clusters, dynamical quantities such as velocity autocorrelation functions, vibrational power spectra, and semiclassical electronic absorption spectra were calculated over a wide energy range, and averaged over a canonical distribution at temperatures in the range T = 5 to 30 K. Electronic absorption spectra were calculated for the origin bands according to the semiclassical method [L. E. Fried and S. Mukamel, J. Chem. Phys. 96, 116 (1992)] and are compared with the corresponding experimental naphthalene . Ar(n) R2PI spectra [T. Troxler and S. Leutwyler, J. Chem. Phys. 95, 4010 (1991)]. The appearance of distinct absorption bands due to specific isomers for a given cluster size, as observed experimentally, is well reproduced by the simulations. Comparison of calculated electronic shifts for different isomers allows clear assignments in the experimental spectra. Increasing the simulation temperature to T = 15-25 K is accompanied by band broadening and the appearance of side-bands towards the blue. Especially strong sidebands appear for naph . Ar2 and all clusters containing the Ar2 subunit, due to large-amplitude surface rotation/translation of the argon dimer on the naphthalene surface, in agreement with experiment. For clusters containing the n = 3 and n = 4 subunits the spectral broadening is smaller. For the n = 4 (4 + 0)-isomer, the calculated band shape increases less than for the other n = 4 isomers, mainly due to the motional narrowing effect of cluster fluxionality. Above 25 K, isomerization between different possible topological structures also occurs by side-crossing motion of one or several argon atoms.