Ion/molecule reactions in the orifice-skimmer region of an atmospheric pressure Penning ionization mass spectrometer.
Ion/molecule reactions in the orifice-skimmer region of an atmospheric pressure Penning ionization mass spectrometer.
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DOI：
10.1002/rcm.2085
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发表时间：
2005-09
期刊：
影响因子：
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通讯作者：
H. Furuya;S. Fujimaki;S. Kambara;Shigeo Suzuki;Yutaka Hashimoto;S. Okazaki;A. Wada;I. Beech;J. Sunner;K. Hiraoka
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文献类型：
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作者：
H. Furuya;S. Fujimaki;S. Kambara;Shigeo Suzuki;Yutaka Hashimoto;S. Okazaki;A. Wada;I. Beech;J. Sunner;K. Hiraoka
测量了第一真空室中Ar或He气体压力、撇油器位置以及小孔与撇油器之间的电压对甲醇常压Penning电离质谱图的影响。当小孔和撇油器同轴，距离为4 mm时，CH3OH2+(CH3OH)n团簇的分布仅与Ar气压(19-220Pa.)和小孔-撇油器电压(1-45V)弱相关。在自由射流膨胀过程中，观察到离子/分子反应CH3OH2++CH3OH--&Gt；CH3+(CH3OH)+H2O，尤其是在较高的小孔撇油器电压下。当小孔和撇油器偏离中心并增加到18 mm时，可以看到大的CH3OH2+(CH3OH)n团簇的形成和解离。吸热式质子转移反应CH3+(CH3OH)+CH3OH-->；CH3OH2++CH3OCH3在较高的孔口撇油电压下发生。在第一真空室中，He气体对团簇离子的碰撞离解比Ar气体诱导的离解有效得多。这些结果表明，质谱图高度依赖于撇渣器位置和孔板撇渣器电压，而质谱学观察到的离子并不一定反映大气压离子源中产生的离子的丰度。
Atmospheric pressure Penning ionization mass spectra of methanol were measured as functions of Ar or He gas pressure in the first vacuum chamber, the position of the skimmer, and the voltage applied between the orifice and the skimmer. When the orifice and the skimmer were coaxial with a distance of 4 mm, the distribution of CH3OH2+(CH3OH)n clusters was only weakly dependent on both Ar pressure (in the range of 19-220 Pa) and orifice-skimmer voltage (in the range of 1-45 V). The ion/molecule reaction CH3OH2+ + CH3OH --> CH3+(CH3OH) + H2O was observed in the free jet expansion, especially at high orifice-skimmer voltage values. When the orifice and the skimmer were off-centered and the distance between them was increased to 18 mm, the formation of large CH3OH2+(CH3OH)n clusters, as well as their dissociation, were seen. The endothermic proton transfer reaction, CH3+(CH3OH) + CH3OH --> CH3OH2+ + CH3OCH3, occurred at high orifice-skimmer voltage. The collision-induced dissociation of cluster ions by He gas in the first vacuum chamber was much more efficient than by Ar. These results demonstrated that the mass spectra are highly dependent on skimmer position and on orifice-skimmer voltage and that ions observed by mass spectrometry do not necessarily reflect the abundance of ions produced in the atmospheric pressure ion source.