Abstract

In molecular beam conditions, we present experimental results of the multiphoton ionization mass spectra of the acetaldehyde molecule in the gas phase by a quadrupole mass spectrometer, using a XeCl excimer laser. From the linear relationships of the intensities of fragment ions to the pressure of sample gas, it can be deduced that the multiphoton ionization fragmentation of the acetaldehyde molecule is a unimolecular process. This result reveals the photochemistry of acetaldehyde in the first single excited state ′(n_π^*): the radicals are all primary products in the UV photolysis of acetaldehyde. We also measure the variation of the intensities of fragmental ions with laser power. Based on these results, we propose the parent molecule dissociation-neutral fragments ionization model of the MPI of acetaldehyde, with which we explain our experimental results.

© 1986 Optical Society of America