title: Emission of M2X+ cluster ions in thermal ionization mass spectrometry in the presence of graphite.
abstract: The emission of M2X+ cluster ions in thermal ionization mass spectrometry when graphite is loaded on the heating filaments was studied. The emission model of non-reductive thermal ionization of graphite was preliminarily discussed and factors influencing the thermal emission of M2X+ ions were investigated. The results show that the intensities of M2X+ cluster ions are related to ionic radius and crystal lattice energy, and possibly also to the solvation energies of ions. The intensities of M2Cl+ (M stands for K, Rb, and Cs) cluster ions, the M2Cl+/M+ ratios, and the 37Cl/35Cl ratios determined from M2Cl+ ion measurement usually increase with measurement time. The variation of the 37Cl/35Cl ratios determined from Cs2Cl+ ion measurement is lower than those based on K2Cl+ and Rb2Cl+ ion measurement, indicating the lowest isotopic fractionation.
authors.affiliation: Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining, China. qhyhyjs@public.xn.qh.cn
authors.forename: Y K
authors.initials: YK
authors.lastname: Xiao
authors.forename: H Z
authors.initials: HZ
authors.lastname: Wei
authors.forename: W G
authors.initials: WG
authors.lastname: Liu
authors.forename: Q Z
authors.initials: QZ
authors.lastname: Wang
authors.forename: Y M
authors.initials: YM
authors.lastname: Zhou
authors.forename: Y H
authors.initials: YH
authors.lastname: Wang
authors.forename: H
authors.initials: H
authors.lastname: Lu