Resonant two photon ionization spectrum of p C_6H_4FCH_3...Ar through the S 1←S 0 transition revealed a number of bands near the origin 0 0 band, and all these bands except for thoes due to the internal rotational transitions of the CH 3 group are assigned to the low frequency external vibrations. Quantum calculations using the method of linear combination of three dimensional harmonic osillator products were carried out to assist the spectral assignments.