The temperature variation of the fractionation of oxygen in exchange reactions between dissolved carbonate and water and between calcite and water and 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.

On the Isotopic Chemistry of Carbonates and a Paleotemperature Scale

羟氨苄青霉素引起大疱性类天疱疮样疹

Uranium solution-mineral equilibria at low temperatures with applications to sedimentary ore deposits

A table is presented of a complete list of the radioactive and stable isotopes, with a number of their salient features, as recorded in the literature or by private communications up to February 1958. (W.D.M.)

Table of isotopes

Electronegativity values from thermochemical data

Correlations of alpha-decay energies in terms of mass number and atomic number have been made for all of the alpha-emitting species now numbering over 100. For each element isotopes show increase in alpha-energy with decrease in mass number except in the region of 126 neutrons where there is an explainable reversal. This reversal has the effect of creating a region of relatively low alpha-energy and long half-life at low mass numbers for such elements as astatine, emanation, francium, and possibly higher elements as had been noted already for bismuth and polonium. Methods and examples of using alpha-decay data to define the energy surface in the heavy element region are discussed. The regularities in alpha-decay are used for predictions of nuclear properties including predictions of the beta-stable nuclides among the heavy elements.

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Systematics of Alpha-Radioactivity

A case of nuclear isomerism in element 43 has been thoroughly studied and is described. An activity of 6.6 hours half-life, which grows from a 67-hour molybdenum activity and has been chemically identified as element 43, decays with the emission of a line spectrum of electrons and no observable nuclear beta-particles. Absorption measurements in aluminum and measurements with a magnetic spectrograph give an energy for the electrons of 116 kev. This line spectrum must be due to the conversion electrons of a highly converted gamma-ray of energy 136 kev and arises as the result of a transition from an excited state of this isotope of element 43. The ground state is either stable or very long-lived. X-rays are also observed, and critical absorption measurements, as well as observations with a bent crystal spectrograph, show that they are to be ascribed to the $K\ensuremath{\alpha}$ line of element 43, as is to be expected from this interpretation. The 6.6-hour activity also emits gamma-rays of about 180 kev energy; the measurements show that these are to be interpreted as following the transition which gives rise to the conversion electrons. A description of the chemical identification of the 6.6-hour activity is given. Other activities of element 43 are mentioned.

Nuclear Isomerism in Element 43

Chemistry of transuranium elements.

Yields for isotopes of Rn through Pu have been measured in the reaction /sup 48/Ca+/sup 248/Cm at an energy of 248--263 MeV (1.04--1.10 times the Coulomb barrier). Despite the low bombarding energy, high and essentially constant integral yields of about 1 to 2 mb for the elements Rn through U were observed. There is evidence that these nuclides are produced with little excitation energy.

Production of cold target-like fragments in the reaction of 48Ca+248Cm.

By the use of a radically new method they have succeeded in identifying unambiguously an isotope of element 102. In other careful experiments conducted over a period of many months they find that they are unable to confirm the element 102 discovery work of Fields et al. reported in 1957. The experiments at Berkeley were performed with the new heavy ion linear accelerator (HILAC) over a period of several weeks and culinated the chemical identification of an isotope of fermium (Fm{sup 250}) as the daughter of an alpha-particle-emitting isotope of element 102 (102{sup 254}). The method used to detect the isotope of element 102 was essentially a continuous milking experiment wherein the atoms of the daughter element 100 were separated from the parent element 102 by taking advantage of the recoil due to the element 102 alpha particle decay. The target consisted of a mixture of isotopes of curium (95% Cm{sup 244} and 4.5% Cm{sup 246}) mounted on a very thin nickel foil. The target was approximately 0.5 mg/cm{sup 2} thick and was covered with 75 {micro}gm/cm{sup 2} aluminum to prevent curium 'knockover'. The curium was bombarded with mono-energetic C{sup 12} ions at energies from 60 to 100 Mev. The transmuted atoms were knocked into helium gas to absorb the considerable recoil energy. It was found that with a sufficient electric field strength practically all of these positively charged atoms could be attracted to a moving negatively charged metallic belt placed directly beneath the target. These atoms would then be carried on this conveyer belt under a foil which was charged negatively relative to the belt. Approximately half of the atoms undergoing alpha decay would cause their daughter atoms to recoil from the surface of the belt to the catcher foil. The catcher foil was cut transversely to the direction of the belt motion into five equal length sections after a time of bombardement suited to the half-life of the daughter atom to be examined. The five foils were then alpha-pulse-analyzed simultaneously in a multiplex assembly consisting of five Frisch grid chambers, amplifiers, a single Wilkinson type 'kick-sorter', and a printer. With this equipment it was easily possible to make all the desired measurements for identifying the atoms caught on the catcher foils and thus to measure the half-life of the parent of the recoiling atoms. The method was first successfully used in bombardments of Pu{sup 240} with C{sup 12} ions to identify a new isotope of element 100, Fm{sup 248}. It was shown to have a half-life of 0.6 minutes by analysis of the amounts of the 20-minute Cf{sup 244} caught on the catcher foils.

Glenn T. Seaborg

Papers

Systematics of Alpha-Radioactivity

Nuclear Isomerism in Element 43

Chemistry of transuranium elements.

Production of cold target-like fragments in the reaction of 48Ca+248Cm.

Element no. 102