空气电导率和离子迁移率谱的吸气电容测量
Aspirated capacitor measurements of air conductivity and ion mobility spectra
摘要：
大气中离子的测量被用来研究大气电和颗粒物污染。通常研究的离子参数是（1）空气传导率，与总离子数浓度有关，以及（2）离子迁移率谱，随大气成分而变化。空气离子仪器的物理原理早已确立。最近的发展是计算机化的吸气式电容器，其测量来自（a）感测电极处的带电粒子的电流和（b）在已知初始电位下与电极的电荷交换速率的离子，所述电荷交换速率松弛到较低电位。随着电压衰减，只有迁移率越来越高的离子被中心电极收集，并有助于电压的进一步衰减。这使得扩展的经典理论计算离子迁移率谱通过反转电压衰减时间序列。在室内空气中，离子迁移率谱确定从这两个新的电压衰减反转，和一个既定的电压开关技术，进行了比较，并显示出相似的形状。通过积分计算的空气电导率分别为：5.3 ± 2.5 fS/m和2.7 ± 1.1 fS/m，通过在恒定电压下直接测量确定的电导率为3 fS/m。新的弛豫势反演方法（RPIM）的应用包括从历史数据中反演空气离子迁移率谱，以及计算行星大气中的离子迁移率谱。
英文摘要：
Measurements of ions in atmospheric air are used to investigate atmospheric electricity and particulate pollution. Commonly studied ion parameters are (1) air conductivity, related to the total ion number concentration, and (2) the ion mobility spectrum, which varies with atmospheric composition. The physical principles of air ion instrumentation are long-established. A recent development is the computerised aspirated capacitor, which measures ions from (a) the current of charged particles at a sensing electrode, and (b) the rate of charge exchange with an electrode at a known initial potential, relaxing to a lower potential. As the voltage decays, only ions of higher and higher mobility are collected by the central electrode and contribute to the further decay of the voltage. This enables extension of the classical theory to calculate ion mobility spectra by inverting voltage decay time series. In indoor air, ion mobility spectra determined from both the novel voltage decay inversion, and an established voltage switching technique, were compared and shown to be of similar shape. Air conductivities calculated by integration were: 5.3 +- 2.5 fS/m and 2.7 +- 1.1 fS/m respectively, with conductivity determined to be 3 fS/m by direct measurement at a constant voltage. Applications of the new Relaxation Potential Inversion Method (RPIM) include air ion mobility spectrum retrieval from historical data, and computation of ion mobility spectra in planetary atmospheres.
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