Major Factors Affecting the Emission of Dilithium-Fluoride Cluster Ion in Thermal Ionization Mass Spectrometry

The process of generating dilithium fluoride ion from the samples of LiF, LiF/C-60, LIF/LiI, and LIF/LiI/C-60 using a double and a triple filament thermal ionization source for a mass spectrometer was studied. This cluster belong to the superalkali class that can form the building block for new nanoscale cluster assembled materials. The results show that in the case of the double filament thermal source when the solution of LiF/C60 was used the Li2F+ ion was detected in the longest temperature range of the evaporation filament. On the other hand, the best abundances of Li2F+ ion was obtained when the solution of LiF/C-60 were loaded on the evaporation filaments of the triple filament thermal ionization source. It has also been found that several different processes are involved in the generation of Li2F+ by the triple filament thermal source: (1) Li2F2 - GT Li2F+ + F; (2) Li+ + LiF - GT Li2F+; and (3) Li+(from LiI) + LiF - GT Li2F+. Reaction (1) is dominant at the low temperatures of evaporation filament (Te), reaction (2) it appears at Te GT 1000 degrees K, for all four above mentioned samples. Reaction (3) appears when the samples were the solution of LiF/LiI and LiF/LiI/C-60 at the high temperature of the evaporation filament