ISOMERIC STRUCTURES, VAN-DER-WAALS FREQUENCIES AND SPECTRAL SHIFTS OF COLD 4-FLUOROSTYRENE-(ARGON)(N) CLUSTERS (N = 1 TO 4)

New spectroscopic results on 4-fluorostyrene (4FSTY) solvated by II argon atoms (n = 1 to 4) have been obtained by resonant two-photon ionization. The spectral features associated with the 4FSTY-Ar cluster have been understood in relation with a fully quantum calculation of the rovibrational states, and those associated with clusters n = 2 to 4 thanks to a classical calculation allowing to find stable isomeric structures. Different isomers have been characterized from their spectral signatures: as was previously shown for aniline-Ar,, van der Waals clusters [P. Hermine, P. Parneix, B. Coutant, F.G. Amar and Ph. Brechignac, Z. Physik D 22 ( 1992) 5291, net isomer specific electronic shifts towards the blue have been observed, which reveal in this case the non equivalence of the binding sites that argon atoms can occupy near the vynilic group substituent.