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High-Resolution Infrared-Vacuum Ultraviolet Photoion and Pulsed Field Ionization-Photoelectron Methods for Spectroscopic Studies of Neutrals and Cations
Xi Xing,Beth Reed,Mi Kyung Bahng,Peng Wang,Hin Koo Woo,Sun Jong Baek,Chee Shing Lam,Cheuk Yiu Ng¤
Author NameAffiliationE-mail
Xi Xing Department of Chemistry, University of California, Davis, Davis, California 95616, USA  
Beth Reed Department of Chemistry, University of California, Davis, Davis, California 95616, USA  
Mi Kyung Bahng Department of Chemistry, University of California, Davis, Davis, California 95616, USA  
Peng Wang Department of Chemistry, University of California, Davis, Davis, California 95616, USA  
Hin Koo Woo Department of Chemistry, University of California, Davis, Davis, California 95616, USA  
Sun Jong Baek Department of Chemistry, University of California, Davis, Davis, California 95616, USA  
Chee Shing Lam Department of Chemistry, University of California, Davis, Davis, California 95616, USA  
Cheuk Yiu Ng¤ Department of Chemistry, University of California, Davis, Davis, California 95616, USA cyng@chem.ucdavis.edu 
Abstract:
We show that by scanning the frequency of a single mode infrared (IR) optical parametric oscillator (IR-OPO) laser to excite the molecular species of interest and fixing the frequency of a vacuum ultraviolet (VUV) laser to photoionize the IR excited species, high-resolution IR spectra of polyatomic neutrals can be obtained with high sensitivity. The fact that this IR-VUV-photoion (IR-VUV-PI) method is based on VUV photoionization probe, and thus, allows the identification of the neutral IR absorber, makes it applicable for IR spectroscopy measurements of isotopemers, radicals, and clusters, which usually exist as impure samples. The highly resolved IR-VUV-PI measurements achieved using the single mode IR-OPO laser have made possible the selection of single rovibrational states of CH3X (X=Br and I), C2H4, and C3H4 for VUV-pulsed field ionization-photoelectron (VUV-PFI-PE) measurements, resulting in rovibrationally resolved photoelectron spectra for these polyatomic molecules. These experiments show that the signal-to-noise ratios of the IR-VUV-PI and IR-VUV-PFI-PE spectra obtained by employing the high-resolution IR-OPO laser are significantly higher than those observed in previous IR-VUV-PI and IR-VUV-PFI-PE studies using a low-resolution IR-OPO laser. Further improvement in sensitivity of IR-VUV-PI and IR-VUV-PFI-PE measurements by using the collinear arrangement of IR-VUV lasers and molecular beam is discussed.
Key words:  Vacuum ultraviolet, Infrared, Pulse-field photoelectron, High resolution
FundProject:
High-Resolution Infrared-Vacuum Ultraviolet Photoion and Pulsed Field Ionization-Photoelectron Methods for Spectroscopic Studies of Neutrals and Cations
邢曦,Beth Reed,Mi-Kyung Bahng,王鹏,胡显冠,Sun-Jong Baek,林周成,伍灼耀¤
摘要:
扫描单模红外光参量振荡(IR-OPO)激光器的波长激发待测分子,并用固定波长的真空紫外(VUV)激光器光电离(PI)探测被红外激发的分子,可获得高灵敏度的中性多原子分子的高分辨红外光谱. 这种方法(IR-VUV-PI)基于真空紫外光电离作为探测,可分辨样品中的不同成分,因此适用于对含同位素,自由基,络合物等通常为非纯的样品进行红外光谱研究. 高分辨的IR-VUV-PI谱可实现对分子单一振转态的选择,在选态的基础上进行真空紫外脉冲场电离零动能光电子谱(VUV-PFI-PE)的研究,可得到高分辨振转解析的光电子谱.被研究的分子包括一卤代甲烷(CH3X(X=Br,I)),乙烯(C2H4),丙炔(C3H4)等. 实验表明,采用高分辨的单模红外光参量振荡器代替先前使用的低分辨红外光参量振荡器可显著的提高IR-VUV-PI和IR-VUV-PFI-PE谱的信噪比. 并进一步讨论了采用IR,VUV,分子束三束同轴以提高IR-VUV-PI和IR-VUV-PFI-PE谱灵敏度的方案.
关键词:  真空紫外,红外,脉冲场光电子,高分辨
DOI:10.1088/1674-0068/21/03/193-201
分类号: