Electronic spectroscopy of para-fluorotoluene clusters

We report (1 + 1) resonance-enhanced multiphoton ionization spectra for clusters of para-fluorotoluene (pFT)n (n = 1–11). After n = 2, the spectra appear to have converged in appearance, suggestive of a dimer chromophore, with weak bonding for subsequent additions of pFT molecules. The spectra also indicate dramatic, vibrational-mode-sensitive changes of oscillator strength between the monomer and the clusters. We also briefly describe the results of probing different parts of the expansion, and varying the laser power.