### 碘甲烷通过Ã态和C态的多光子电离

1. 分子反应动力学国家重点实验室，中国科学院化学研究所，北京 100080
• 收稿日期:1993-03-22 修回日期:1993-04-05 发布日期:1993-08-15
• 通讯作者: 杨达林

### Methyl Iodide Multiphoton Ionization Via Ã State or C State

Yang Da-Lin; Ling Yun; Ding Chuan-Fan; Zhou You; Zhu Qi-He

1. State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080
• Received:1993-03-22 Revised:1993-04-05 Published:1993-08-15
• Contact: Yang Da-Lin

Abstract: The collision-free multiphoton ionization of jet cooling CH_3I was studied using a pulsed laser, tunable around 280 and 366 nm with TOF mass spectrometer and mag-netic-bottle TOF photoelectron spectrometer.
MPI of CH_3I in 280 nm region via valence Ã state can be explained by ladder-switch mechanism according to the following experimental results. The parent ions are almost abscent in the MPI TOF MS. I~+ MPI spectrum gives three resonances corre-sponding to two-photon excitation of I atom at 279.72, 279.25 and 278.50 nm. The I ionic state due to 2+1 REMPI of I atom can be assigned from the REMPI PES.
In 371—365 nm I~+, CH_3~+ and CH_3I~+ were observed in MPI MS. The mass-selected MPI spectra of CH_3I~+ and daughter ion I~+ have similar profiles. In the spectra the two peaks at 365.90 and 369.92 nm are assigned to be two-photon resonance with the Rydberg C state Π(0,0) and Σ(0,0) of CH_3I respectively. The formation of the CH_3I~+ ~2Π_(3/2) and ~2Π_(1/2) state created by 2+1 and 2+2 REMPI resectively were found in PES. REMPI of CH_3I around 366 nm is consistent with the ladder mechanism in which CH_3I is excited into C state upon a two photon absorption and parent ion is formed by the overall 2+1 of 2+2 MPI process. The fragment ions are produced by further dissociation of CH_3I~+ at Ã state.