Clusters of Ar bound to isomers of the aromatic hydrocarbon n-butylbenzene (BB) have been studied using two-color REMPI (resonance enhanced multiphoton ionization) and MATI (mass analyzed threshold ionization) spectroscopy to explore noncovalent. vdW interactions between these two moieties. Blue shifts of excitation energy were observed for gauche-BB...Ar clusters, and red shifts for anti-BB center dot center dot center dot Ar clusters were observed. Adiabatic ionization energies (IEs) of the conformer BB-I center dot center dot center dot Ar and BB-V center dot center dot center dot Ar were determined as 70052 and 69845 +/- 5 cm(-1), respectively. Spectral features and vibrational modes were interpreted with the aid of UMP2/cc-pVDZ ab initio calculations. Data of complexation shifts of the alkyl-benzenes and their argon clusters were collected and discussed. Using the CCSD(T) method at complete basis set (CBS) level, interaction energies for the neutral ground states of BB-I center dot center dot center dot Ar and BB-V center dot center dot center dot Ar were obtained as 650 and 558 cm(-1), respectively. Combining the CBS calculation results and the REMPI and MATI spectra allowed further the determination of the interaction energies and the energetics of BB center dot center dot center dot Ar in the excited neutral S-1 and the D-0 cationic ground states.