碘代烷烃在532nm激光作用下多光子电离解离机理

Multiphoton lonization Mass Spectra of Alkyl Iodides at 532 nm

利用532nm的激光对碘代烷烃(碘甲烷,碘乙烷,碘代正丙烷,碘代异丙烷)分子作了多光子电离解离(MPID)质谱(MS)研究.在532nm激光作用下,CH_3I分子吸收532nm激光双光子的能量,进入A带的1A_2态,继续吸收光子上泵浦至电离态形成母体离子CH_3I^+,然后再形成碎片离子;而其它几个碘代烷烃吸收双光子的能量进入A带后均形成中性碎片,中性碎片再吸收光子经一系列电离解离形成碎片离子.此外,本文还通过对同分异构分子n-C_3H_7I与i-C_3H_7I分支比的分析给出i-C_3H_7I分子的可能的电离解离通道.

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 532 nm. 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 molecules 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.