A novel optical emission spectroscopy method for diagnostics of contribution of different ionization mechanisms and flux of ions in different valences in discharge channel of a Hall thruster

The mass application of Hall thrusters poses the need for a diagnostic method of ionization mechanism in the discharge channel to boost the iteration and optimization of thruster design.This work presents an Optical Emission Spectroscopy (OES) method for diagnostics of the contribution of different ionization mechanisms and the flux of ions in different valences in the discharge channel of a Hall thruster.The emission spectra in the discharge channel are analyzed by jointly utilizing a collisional-radiative model,an ionization-excitation model,and a flux-conservation model.It is found that the intensities of some spectral lines can be converted into the reaction rates of collision processes,e.g.,electron-induced excitation and ionization processes.The latter can further be used to determine the evolutions of particle fluxes by utilizing the conservation law of matter.The novel method is demonstrated on a kilo-watt Hall thruster.The evolutions of several parameters are determined using this method along the discharge channel,including the ionization rates of different mechanisms,particle fluxes,particle densities,and particle velocities.This novel method can be further developed by being jointly utilized with spectral imaging and tomography techniques,enabling diagnostics of multi-dimensional distributions of the above-mentioned parameters in the discharge channel and near-field plume.

Crystal Structure and Mass Spectrometric Fragmentation Behavior of Eprosartan

The crystal structure determination and mass spectrometric fragmentation analysis of the medicinal ingredient eprosartan （4-[2-butyl-5-（2-carboxy-3-thiophen-2-yl-propenyl）-imidazol-l-ylmethyl]-benzoic acid） are presented. The single-crystal X-ray diffraction shows that the colorless transparent crystal of eprosartan is of monoclinic system, space group P2/c with a = 16.1861（15）, b = 10.9813（12）, c = 28.610（3） A, β = 118.452（2）°, Z = 4, V= 4471.1（8） A3, Dc = 1.288 g/cm3,μ（MoKα） = 0.178 mm^-1 and F（000） = 1831. The independent part of the unit cell contains two eprosartan molecules and one unordered H2O molecule in the crystal structure which is fixed by inter- and intramolecular hydrogen bonds. The product ions in electrospray ionization tandem mass spectrometry （ESI-MSn） displays the protonated eprosartan dissociated in three competitive pathways and the fragmentation mechanism is proposed and supported by the FTICRMSn results.

Characterization of particulate products for aging of ethylbenzene secondary organic aerosol in the presence of ammonium sulfate seed aerosol

Aging of secondary organic aerosol（SOA） particles formed from OH– initiated oxidation of ethylbenzene in the presence of high mass（100–300 μg/m^3） concentrations of（NH_4）_2SO_4seed aerosol was investigated in a home-made smog chamber in this study.The chemical composition of aged ethylbenzene SOA particles was measured using an aerosol laser time-of-flight mass spectrometer（ALTOFMS） coupled with a Fuzzy C-Means（FCM） clustering algorithm.Experimental results showed that nitrophenol,ethyl-nitrophenol,2,4-dinitrophenol,methyl glyoxylic acid,5-ethyl-6-oxo-2,4-hexadienoic acid,2-ethyl-2,4-hexadiendioic acid,2,3-dihydroxy-5-ethyl-6-oxo-4-hexenoic acid,1H-imidazole,hydrated N-glyoxal substituted1H-imidazole,hydrated glyoxal dimer substituted imidazole,1H-imidazole-2-carbaldehyde,N-glyoxal substituted hydrated 1H-imidazole-2-carbaldehyde and high-molecular-weight（HMW） components were the predominant products in the aged particles.Compared to the previous aromatic SOA aging studies,imidazole compounds,which can absorb solar radiation effectively,were newly detected in aged ethylbenzene SOA in the presence of high concentrations of（NH_4）_2SO_4seed aerosol.These findings provide new information for discussing aromatic SOA aging mechanisms.