Multiphoton ionization mass Spectra of alkyl Iodides at 532 nm

Multiphoton Ionization-Dissociation (MPID) Mass Spectra (MS) of alkyl iodid es (including methyl iodide, ethyl iodide, n-propyl iodide and i-propyl iod ide) are obtained using a time-of-flight mass spectrometer at 532 nm. It is found that all kinds of parent molecules are first two-photon resonantly e xcited to A-band. CH3I molecule is resonantly exited to 1A(2) state of A-ba nd, and its MPID belongs to parent-ion ladder mechanism. However other mole cules are resonantly exited to A-band and then go through dissociation. Fra gment ions are produced by ionization and dissociation of neutral fragments , Their MPID belongs to neutral-fragment photoionization mechanism. Moreove r, the dissociation pathways of isopropyl cation are discussed through bran ching ratio analyses.