Near-infrared excitation of alkane ultra-violet fluorescence

We report the generation of ultra-violet fluorescence from linear and cycli c saturated hydrocarbons in neat solution when excited with femtosecond nea r-infrared laser pulses at 800 nm. Fluorescence decay, spectra and power de pendence studies are reported. Steady-state and time-resolved experiments a re in agreement with previously reported data obtained with one-photon vacu um ultra-violet, X-ray, electron impact and two-photon excitation. Our resu lts indicate that the mechanisms leading to the fluorescing excited state a re multi-photon absorption and ionisation with the latter followed by diffu sion-controlled geminate cation-electron recombination. (C) 1999 Elsevier S cience B.V. All rights reserved.