Positive ray analysis

In its simplest form, a mass spectrometer is an instmment that measures the mass-to-charge ratios ml of ions formed when a sample is ionized by one of a number of different ionization methods (1). If some of the sample molecules are singly ionized and reach the ion detector without fragmenting, then the ml ratio of these ions gives a direct measurement of the molecular weight. The first instmment for positive ray analysis was built by Thompson (2) in 1913 to show the existence of isotopic forms of the stable elements. Later, mass spectrometers were used for precision measurements of ionic mass and abundances (3,4). 

W. Bleakney. A New Method of Positive Ray Analysis and Its Application to the Measurement of Ionization Potentials in Mercury Vapor. Phys. Rev., 34(1929) 157-160. 

THE IONIZATION POTENTIALS OF HYDROGEN AS INTERPRETED BY POSITIVE RAY ANALYSIS... 

General Description of Method.— The gas is ionized by impact electrons emitted by a hot tungsten filament, and, by means of an electric field the positive ions formed are drawn through a narrow slit into a magnetic field, where they are resolved into constituents of different ratios of charge to mass by a method very similar to that employed by Dempster in his positive ray analysis. The ionization potential necessary to produce each ion is determined by gradually reducing the potential applied to the impact electrons until no trace of the particular ion can be detected. 

Positive ray analysis of the products of ionization in hydrogen shows that under proper conditions Hs" " ions are far more numerous than H2 ions. Prompted by this result the writers have been attempting to discover whether or not any part of the secondary spectrum might be attributed to Ha or Ha". Such a possibility has been discussed in connection with some of the attempts to arrange the lines in series but has not, we believe, been subjected to experimental scrutiny. 

Using his positive ray analysis,. 1.. 1. Thomson hits shown that atmospheric neon contains two isntojtes, one with an atomic weight 20 and the other 22. This conclusion has Item confirmed by Aston, a who obtained evidence of two isotojs H of atomic weights 20 and 22 in proportion ) to 1. This accounts for the accepted value of 20.2, There is also some evidence of a third isotope of value 21, comprising about 1 kt cent of the whole. If this conclusion is confirmed this would furnish mi interesting triad somewhat similar to those found in (Jroup VIII. 

Davis R, Schaeffer OA (1955) Chlorine-36 in nature. Ann New York Acad Sci 62 105-122 Dempster AJ (1918) A new method of positive ray analysis. Phys Rev 11 316-325 Dickin AP (1995) Radiogenic Isotope Geology. Cambridge University Press, Cambridge... 

Dempster, A. J. 1922. Positive ray analysis of potassium, calcium, and zinc. Phys. Rev. 20 631-638. 

Bleakney, W. (1929) A new method of positive ray analysis and its application to the measurement of ionization potentials in mercury vapor. Physical Review, 34, 157-160. 

Hogness, T.R., Lunn, E.G. (1924) The ionization potentials of hydrogen as interpreted by positive ray analysis. Proceedings of the National Academy of Sciences of the United States of America, 10,398-405. 

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