Correlation of the isotope chemistry of hydrogen, carbon, and oxygen with molecular forces by the WIMPER (2) method Isotope chemistry and molecular structure. Carbon and oxygen isotope chemistryThe temperature variation of the fractionation of oxygen in exchange reactions between dissolved carbonate and water and between calcite and water are calculated on theoretical grounds, and checked experimentally. In the course of the experiments it was necessary to investigate several methods of decomposing calcium carbonate to carbon dioxide for mass spectrometer analysis. A method was developed for growing calcium carbonate from solution with the same isotopic composition as the carbonate shells of organisms produced at the same temperature from water of the same isotopic composition, and the results of these experiments at various temperatures are expressed in an equation relating the temperature of formation with the isotopic composition of the calcium carbonate and of the water. a = 3[ COS18= J+ 2[ COl60218= J+ [C02l60l8= J / [H20l8J . 3[ CO a l8= J+ 2[ C0 2 16Q18= J+ [COl60 2 l8= J [H 2 016J

A Nier-type mass spectrometer and its associated electronic units have been constructed for the purpose of measuring small variations in the abundances of oxygen of mass 18 and of carbon of mass 13 in carbon dioxide, and of oxygen of mass 18 in oxygen gas, to an accuracy of ±0.01 percent of the abundance of these isotopes. The electronic units of the necessary stability for this degree of accuracy are described. A gas feed system is described which permits fast alternate introduction of the sample of gas to be analyzed and a standard gas into the mass spectrometer. All measurements of the variation in the abundance of the oxygen and carbon isotopes are made with reference to a standard.

The role of the ion-sensitive plate as an ion detector in contemporary mass spectrometers or spectrographs is discussed in this paper. The plates are mainly used in instruments of the Mattauch–Herzog geometry for detecting ions with mass-to-charge ratios from 1 to well over 1000. The energies of the ions detected usually lie in the range from 5 to 75 keV. The type Q2 low-gelatin plate is widely used in both organic structure studies by the electron bombardment method and elemental analysis of metals and inorganics by the spark source method. In addition to detectors with low-gelatin emulsions, those with centrifuged emulsions or vapor deposited films are also used for special applications, as are ion-to-light and ion-to-electron converters.

As part of a research program in spark-source solids mass spectrometry, the photon and ion response characteristics of various types of detector plates have been determined. Outgassing behavior of the plates in high-vacuum service has also been evaluated by empirical tests in a mass-spectrometer system. Conventional ion-sensitive plates are compared and contrasted on the basis of log-probability response curves. Various development procedures are classified by the nature of the response curves and by the extent of processing fog. Coating analyses and microstructure are related to the response properties of some emulsions. Development of an emulsion with much higher ion sensitivities than the present SWR and Q plates is forecast.

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