Here we report on a laser plasma-based tunable VUV photoionization time-of-flight (TOF) mass spectrometer conceived mainly to study complex gaseous mixtures. Ionizing photons at tunable vacuum UV (VUV) wavelengths are generated by a gas-target laser-produced plasma, spectrally dispersed in the range 100–160 nm and efficiently focused onto a sample molecular beam. As a test case, we studied the exhaust gas of a four-stroke moped, a typical example of a complex gaseous mixture. Due to the VUV “soft” ionization, the mass spectra are less congested and more easily interpretable. Substituted benzene derivatives are found to give the most intense signals. Several aliphatic hydrocarbons are also detected. The use of tunable VUV radiation allowed the investigation of the contribution of isomers in the mass spectrum from the onset and shape of the photoionization efficiency spectra. Semiquantitative analysis was performed using known literature data detailing the photoionization cross sections. Our findings suggest that using combined data on the mass/photoionization efficiency spectra may be very helpful for a comprehensive analysis of complex gaseous mixtures.

在这里，我们报告了一种基于激光等离子体的可调谐 VUV 光电离飞行时间 (TOF) 质谱仪，其主要用于研究复杂的气体混合物。可调谐真空紫外 (VUV) 波长的电离光子由气体目标激光产生的等离子体产生，光谱分散在 100-160 nm 范围内，并有效地聚焦到样品分子束上。作为测试案例，我们研究了四冲程轻便摩托车的废气，这是复杂气体混合物的典型例子。由于 VUV“软”电离，质谱不那么拥挤并且更容易解释。发现取代的苯衍生物给出最强烈的信号。还检测到几种脂肪烃。可调谐 VUV 辐射的使用允许从光电离效率谱的开始和形状研究异构体在质谱中的贡献。使用详述光电离截面的已知文献数据进行半定量分析。我们的研究结果表明，使用质量/光电离效率谱的组合数据可能对复杂气体混合物的综合分析非常有帮助。