PUMP-PROBE LASER PHOTOLYTIC FRAGMENTATION FLUORESCENCE SPECTROMETRY OF METHYL VINYL KETONE, METHACROLEIN AND CROTONALDEHYDE

The two-laser ''pump-probe'' photolytic fragmentation fluorescence spe ctrometry of methyl vinyl ketone, methacrolein and crotonaldehyde is d escribed. Probe laser induced C-2 (C-1 Pi(g) --> A(3) Pi u, Deslandres -d'Azambuja band system) fluorescence is detected. The relative C-2 fl uorescence intensity and spectral patterns exhibited by each C4H6O iso mer are dependent upon the probe laser wavelength employed. The depend ence of the fragment fluorescence signal intensity on the probe laser fluence implies that the ''probe'' laser induces photofragmentation of intermediate specie(s) produced by the ''photolysis'' laser. The viny l radical (C2H3) is believed to be an important intermediate produced from the C4H6O isomers by the photolysis laser, which can subsequently be converted to C-2 via the absorption of probe laser photons.