Cycloidal Mass Research Articles

Cross sections for the production of N 2+, N + and N 22+ from nitrogen by electrons in the energy range 16–600 eV

Cross sections were determined for the production of N 2 +, N 2 2+ by electrons from molecular nitrogen in the energy range from 16 through 600 eV, using a cycloidal mass spectrometer with total ion transmission. The investigation of the reaction N 2 + e → N 2 2+ + 3e was made possible by using isotopically enriched nitrogen. At 430 eV electron energy a sudden increase in the cross section for N 2 2+ was found , due to an Auger process.

Partial ionization cross sections of carbon dioxide by electrons (25–600 eV)

Measurements were made of the partial ionization cross sections of CO 2 +, CO +, O +, C + and O 2 +, originating from ionization of CO 2 by electrons of 25–600 eV. Total collection of these ions was achieved by using a cycloidal mass spectrometer. The relative measurements were normalized, using absolute values of the total cross sections from the literature.

Evidence for a continuum of rate constants for gaseous unimolecular ion reactions

Decay curves of product ion intensity versus lifetime have been obtained for twenty metastable transitions using a cycloidal mass spectrometer by the method of Benz and Brown. Consistent with the quasi-equilibrium theory, but in contrast to previous evidence from this method, none of these data supports the existence of only one or two discrete rate constants for ion decomposition. A new method is utilized which increases the sensitivity and the range of measurable lifetimes for metastables by defocusing the ordinary product ions.

Observation of Metastable Ions in a Cycloidal Mass Spectrometer

The line shapes that result from metastable-ion transitions in a cycloidal mass spectrometer are discussed and some half-lives of metastable ions are determined by a new method.

A cycloidal mass spectrometer with 100% collection efficiency

A simple cycloidal mass spectrometer has been built for measuring absolute ionization cross sections of gases. To avoid any mass discrimination, the ion source is deprived of slits. Thus we assume a complete collection of all ions of a certain mass is obtained at the collector. Measurements show that the ion currents to the collector are largely independent of the instrumental setting.

Excess radiogenic argon in fluid inclusions

Most minerals, with the possible exception of micas, commonly contain fluid inclusions, Argon contained in such inclusions may be considered a possible source of error in dating very young or low potassium minerals by the K-Ar method. Wahler [1956] first demonstrated spectrographically the presence of Ar in fluid inclusions in quartz. Elinson and Polykovskii [1961, 1963] used a vacuum ball mill to extract the gases present in fluid inclusions in various pegmatite minerals. They obtained Ar from quartz in quantities up to 8.9×10−3 cc/g. Preisinger and Huber [1964] state that they determined the Ar content of the gas emitted by heating very small samples (10−6 g) of feldspar crystals from a granite in a cycloidal mass spectrometer. The total gas emitted (water-free basis) varied from 0.8 to 3.3×10−3 cc/g. Nesmelova [1959] found up to 1.7% (Ar + Kr + Xe) in the gas from gas inclusions in sylvites from the Bereznikovsk mine in the USSR. Hoy et al. [1962] found 0.4 volume % Ar in the gases of highpressure gas inclusions in ‘popping-salt’ from the Winnfield salt dome in Louisiana. Sample weight and total gas volume were not specified. Damon and Kulp [1958] extracted excess radiogenic Ar from beryl, cordierite, and tourmaline in quantities ranging from 10−5 cc/g to 10−2 cc/g, some of which was assumed to come from fluid inclusions (p. 449). Lippolt and Gentner [1963] reported the finding of excess radiogenic Ar of the order of 10−7 cc/g in several fluorite samples and indicated that much of the excess was probably contained in fluid inclusions.