Multiphoton Ionization-Dissociation (MPID) Mass Spectra (MS) of alkyl iodides (including methyl iodide, ethyl iodide, n-propyl iodide and i-propyl iodide) are obtained using a time-of-flight mass spectrometer at 532nm. It is found that all kinds of parent molecules are first two-photon resonantly excited to A-band. CH3I molecule is resonantly exited to 1A2 state of A-band, and its MPID belongs to parent-ion ladder mechanism. However other moleculles are resonantly exited to A-band and then go through dissociation. Fragment ions are produced by ionization and dissociation of neutral fragments. Their MPID belongs to neutral-fragment photoionization mechanism. Moreover, the dissociation pathways of isopropyl cation are discussed through branching ratio analyses.

Key words: IODOHYDROCARBON, LASER APPLICATION, LASER, MULTIPHOTON PROCESSES, IONIZATION