Assumption Of Ionization Research Articles

Investigation of ion cluster formation in a pulsed ion mobility spectrometer operating in the negative mode

Ion mobility spectrometry (IMS) is a well-known technique for fast trace gases detection. Employing atmospheric pressure chemical ionization in IMS, ion clusters, e.g. protonated monomer or proton bound dimer analyte ions such as MH+(H2O)n or M2H+(H2O)n form in the positive mode, where the chemical ionization is based on positively charged reactant ions H+(H2O)n. In the negative mode, where the ionization is based on negatively charged reactant ions O2-(H2O)n, similar cluster formation is possible but less common. In this paper, we investigate 2-chlorophenol, formic acid and toluene-diisocyanate as single substances and in mixtures, showing their different behavior regarding the formation of symmetric and asymmetric clusters and thus the presence and absence of additional peaks in the ion mobility spectra. Quantum-chemical calculations regarding the stabilization energy can explain the absence of certain cluster signals quite well when based on the assumption of ionization by electron capture in contrast to the typically expected ionization by proton abstraction.

カスプ磁場を用いたイオンスラスターの放電プラズマ

Discharge plasmas in magnetic cusp ion thrusters were studied. To evaluate ion loss rates to the chamber wall, ion density distributions were measured by a Langmuir probe scanned along the wall surface. Comparisons of discharge perfomances were made for various electrode geometries, anode configurations and two different magnetic field strengths. A simple discharge plasma model based on the assumption of ionization by primary electrons was applied to investigate the cusp confinement for the wall and ring anode configurations.

Mechanism of the Geiger discharge.

IN the original theory of Townsend, the discharge phenomena in the Geiger counter are explained on the assumption of ionization by electrons (α ions per cm.) followed by an ionization by positive ions (β ions per cm.). Later this theory, especially as a consequence of the fact that ionization by positive ions requires a high energy, was modified in such a way that the secondary process was considered to consist of electrons liberated from the cathode by photons from the primary avalanche (θηg photoelectrons from one field electron per cm. path). Both theories give analogous mathematical expressions for the sparking equation and for the current amplification in the homogeneous field between plane surfaces. Thus it is impossible to decide between the two possibilities.