Häufigkeitsverteilungen von einfach und doppelt positiv geladenen molekülionen ausgewählter chemischer elemente im funkenplasma

Abstract

The knowledge of the abundance distribution and intensities of molecular ions has been of special interest for mass spectrographic trace analysis. A double-focussing mass spectrograph has been used to measure the intensities of carbide, oxide and dimer cluster ions for the IVa, IIIb and VIb elements, iron, nickel, silver, tantalum, bismuth and uranium. For some elements a typical alternating abundance distribution of carbide ions, MC_n⁺, was found which is comparable with the distribution of carbon cluster ions in a high temperature plasma.

Whereas singly-charged molecular ions with relative abundances of ⩽ 10⁻² were observed the doubly-charged molecular ions could be measured to the order of magnitude of ⩽ 10⁻⁴.

Triply-charged molecular ions of the investigated elements were not formed in the mass spectra (detection limits ⩾ 10⁻¹⁰). We can conclude that either triply-charged molecular ions are not formed in a high temperature plasma or that their lifetime is lowered with the time-of-flight through the mass spectroscopic system.