Recently, Research Center for Environmental Materials and Pollution Control Technology of University of Chinese Academy of Sciences (UCAS) successfully developed a new microchannel-extreme ultraviolet (MCP-EUV) light source and applied it to a mass spectrometer. The light source can produce high-flux extreme ultraviolet (EUV) light, which breaks through the technical bottleneck that the window material of traditional vacuum ultraviolet (VUV) light sources cannot transmit EUV light with wavelength <115 nm. The relevant research results were published in Analytical Chemistry 2023 95 (45) 16531-16538 entitled "Novel MCP-Windowed EUV Light Source and Its Mass Spectrometric Application for Detecting Chlorinated Methanes". The paper was selected as a supplementary journal cover article. CHENG Shiyu, a graduate student from our school, is the first author. Associate Professor YANG Bo and Professor SHU Jinian are the corresponding authors.
VUV and EUV light sources play important roles in many fields, such as chemical analysis, basic physics research, and chip manufacturing. Noble gas discharge lamps are a kind of widely used VUV light sources. In principle, a variety of light radiations with wavelengths covering VUV (100−200 nm) and EUV (10−120 nm) ranges can be generated by exciting different noble gases. However, the absorption of high-energy photons in the EUV range by the commonly used MgF2 window material limits the effective transmission and utilization of EUV light. Some low-molecular-weight organics with ionization energies higher than the transmission limit (115 nm, 10.8 eV) of the window material are in the blind area of traditional VUV photoionization analytical methods. Though windowless light sources can transmit any wavelength of light, the discharge gas inside the light source will leak into the analysis system, affecting the detection efficiency of the instrument and increasing the burden of the vacuum system. To expand the output wavelength range of the VUV light source and reduce the leakage rate of the discharge gas, the research team has proposed an innovative method to transmit EUV light via a micro-channel plate (MCP) and successfully developed an EUV light source with a photon flux of more than 1014 photons s-1. The new light source uses neon gas as the discharge gas. The time-of-flight mass spectrometer coupled with the EUV light source can directly detect high-ionization-energy organic compounds such as chloromethanes. The detection limit reached pptv level within 30 s of measurement time. This technique provides a new analytical approach for the real-time detection of ozone-depleting species and greenhouse gases such as fluorine and chlorinated hydrocarbons.
The new MCP-EUV light source can output a variety of VUV and EUV lights, such as 53.7/58.4 nm (helium line), 73.6/74.3 nm (neon line), 104.8/106.7 nm (argon line), 116.5/123.6 nm (Krypton line), and 129.5/147.6 nm (xenon line). In addition, by choosing other kinds of gas as the discharge gas, the light source can output more wavelengths of light. The above research provides a new EUV light source technology for scientific research and industrial applications in related fields.
The research work was supported by the National Natural Science Foundation of China (22076184; 21527901), the Research Equipment Development Project of the Chinese Academy of Sciences (YJKYYQ20180072), and the Fundamental Research Funds for the Central Universities.
The link to the paper: https://doi.org/10.1021/acs.analchem.3c02365
Fig 2. Gated EUV photoionization mass spectra of 100 ppbv CH3Cl (A), CH2Cl2 (B), CHCl3 (C), and CCl4 (D) in synthetic air.
Author: Research Center for Environmental Materials and Pollution Control Technology
Editor: GAO Yuan