We present a computational simulation of a helium DC glow discharge used as an ambient desorption/ionization source for mass spectrometry. Both the fluid dynamics of the flowing gases and the kinetics of the chemical reactions are modeled. The simulation incorporates measured absolute number densities of helium metastable atoms obtained using an atomic absorption spectrometer. The results indicate that the formation of protonated water cluster ions, (H₂O)_nH⁺, begins shortly downstream from the high voltage pin electrode in the active discharge region. The (H₂O)_nH⁺ ions grow in size as they flow with the helium. Several key parameters were changed to observe their effect on the formation of (H₂O)_nH⁺ ions, including the concentration of nitrogen and water impurities in the helium plasma gas, the relative humidity of the air around the discharge tube, and the air pressure. Changing impurity levels in the plasma gas had the largest effect on the formation of water clusters. Changes in ambient humidity levels affected the size of the (H₂O)_nH⁺ ions, but not the overall number of ions. Changes in air pressure did not have a significant effect.

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直流辉光放电作为质谱的环境解吸/电离源的计算模型

我们提出了氦直流辉光放电的计算模拟，该放电用作质谱仪的环境解吸/电离源。对流动气体的流体动力学和化学反应动力学都进行了建模。该模拟结合了使用原子吸收光谱仪测得的氦亚稳定原子的绝对数密度。结果表明，质子化水团簇离子（H ₂ O）_n H ^+的形成开始于有源放电区中高压针状电极的下游。（H ₂ O）_n H ⁺离子随着氦气的流动而增大。更改了几个关键参数以观察它们对（H ₂ O）_n H ⁺离子形成的影响，包括氦等离子体气体中氮和水杂质的浓度，放电管周围空气的相对湿度以及空气压力。等离子气体中杂质含量的变化对水团簇的形成影响最大。环境湿度水平的变化会影响（H ₂ O）_n H ⁺离子的大小，但不会影响离子的总数。气压的变化没有显着影响。