Pump-probe laser photolytic fragmentation fluorescence spectrometry of methyl vinyl ketone, methacrolein and crotonaldehyde

The two-laser “pump-probe” photolytic fragmentation fluorescence spectrometry of methyl vinyl ketone, methacrolein and crotonaldehyde is described. Probe laser induced C2 (C1IIg→A1IIu9 Deslandres-dʹAzambuja band system) fluorescence is detected. The relative C2 fluorescence intensity and spectral patterns exhibited by each C4H6O isomer are dependent upon the probe laser wavelength employed. The dependence 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 vinyl radical (C2H3) is believed to be an important intermediate produced from the C4H6O isomers by the photolysis laser, which can subsequently be converted to C2 via the absorption of probe laser photons.