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The ionization sequences of alkaline iodides in a double-filament surface-ionization mass spectrometry system were studied. The test samples were strontium iodide and barium iodide. The ionization parameters, ϵ, at the surface of the ionization filament (IF) ϵ were determined by Arrhenius’ plots. It was found that ionization parameters are dependent on evaporation filament (EF) temperature. This phenomenon is the same as that observed in the case of calcium iodide in our previous study. The findings can be explained in the following way. At low EF temperatures, the sample vapor arrives at the ionization filament in the chemical form in which the sample was initially loaded on the EF. Therefore, the sample vapor must gain the sum of dissociation and ionization energies at the IF. At high EF temperatures, the sample vapor can dissociate on or near the EF. As a result, the apparent ionization parameters changed with the EF temperature. |
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