CH2Br2的同步辐射光电离研究:10—12eV范围内CH2Br2的振动自电离态

报道在超声射流冷却条件下用同步辐射ＶＵＶ光源研究ＣＨ₂Ｂｒ₂的振动自电离结构．根据测量的１０５—１２３ｎｍ范围内母体离子（ＣＨ₂Ｂｒ₂⁺）的光电离产率曲线，获得ＣＨ₂Ｂｒ₂的绝热电离势为１０.２３±０.０１ｅＶ．ＣＨ₂Ｂｒ₂⁺的最低三个电子激发态，即Ａ（²Ａ₂），Ｂ（²Ｂ₁），Ｃ（²Ａ₁）分别位于１０.７８±０.０１ｅＶ，１１.２０±０.０１ｅＶ和１１.２７±０.０１ｅＶ．在１１５.０１—１２１.１５ｎｍ范围内，观察到ＣＨ₂Ｂｒ₂自电离峰叠加在若干台阶结构上，台阶平均宽度为７１６.８±４０.０ｃｍ^-1，对应于ＣＨ₂Ｂｒ₂⁺（Ｘ²Ｂ₂）中Ｂｒ-Ｃ-Ｂｒ反对称的伸缩振动（ｖ₉），所有的峰均归属为收敛于ＣＨ₂Ｂｒ₂⁺（Ｘ²Ｂ₂，ｖ⁺）振动能级的ｎｓ，ｎｐ和ｎｄ自电离Ｒｙｄｂｅｒｇ态．此外，对ＣＨ₂Ｂｒ₂光解离电离产生离子型自由基ＣＨ₂Ｂｒ⁺（Ｘ）的光电离产率曲线的结构也进行了归属 关键词：

PHOTOIONIZATION STUDIES OF DIBROMOMETHANE USING SYNCHROTRON RADIATION: A STUDY OF VIBRATIONAL AUTOIONIZATION STATES FOR CH2Br2 IN 10-12eV

The vibrational autoionization stucture of dibromomethane has been investigated in the supersonic beam conditions using ＶＵＶ synchrotron radiation. Based on photoionization efficiency curve of ＣＨ₂Ｂｒ₂⁺ in １０５—１２３ｎｍ we have found that the adiabatic ionization potential(IP) of the dibromomethane is １０.２３±０.０１ｅＶ．The thresholds at １０.７８±０.０１ｅＶ，１１.２０±０.０１ｅＶ and １１.２７±０.０１ｅＶ ware identified as the electronically excited states of ＣＨ₂Ｂｒ₂⁺,i.e., Ａ（²Ａ₂），Ｂ（²Ｂ₁） and Ｃ（²Ａ₁） states. The discrete peaks with some autoionization features superposed on a step-like structure in the PIE curve of the parent ion were observed in the range of １１５.０１—１２１.１５ｎｍ. The average step width was about ７１６.８±４０.０ｃｍ^-1，which was in good agreement with the value of the vibrational frequency of the Ｂｒ-Ｃ-Ｂｒ antisymmetrically stretching motion （ｖ₉） of the parent ion ＣＨ₂Ｂｒ₂⁺（Ｘ²Ｂ₂) which was measured by infrared absorption method. All strong peaks ware assigned to the autoionization, ｎｓ，ｎｐ and ｎｄ Ｒｙｄｂｅｒｇ states converging to various vibrationally excited states of the ground state of ＣＨ₂Ｂｒ₂⁺. In addition, the vibrational modes and autoionization structure occurring in the ground electronic state of the daughter ion ＣＨ₂Ｂｒ⁺（Ｘ）were also assigned.