Fluorescence intensity decays of cyclohexane and methylcyclohexane with two‐photon excitation from a high repetition rate frequency‐doubled dye laser

We observed fluorescence emission from cyclohexane (CH) and methylcyclohexane (MCH) using picosecond pulses at 298–300 nm from a frequency‐doubled cavity‐dumped R6G dye laser. The emission maxima for CH and MCH are 209 and 215 nm, respectively, which agree with previous studies using vacuum ultra‐violet (VUV) excitation near 150 nm. The fluorescence intensities depended quadratically on peak laser intensity indicating two‐photon excitation. The intensity decays resulting from two‐photon excitation were measured using frequency‐domain fluorometry and were found to be nearly singly exponential ranging from 0.59 to 0.80 ns. Two‐photon induced fluorescence of cyclic and linear alkanes may provide new intrinsic spectroscopic probes of biological molecules. © 1995 John Wiley & Sons, Inc.