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This mistake was indirectly corrected by Scharff-Goldhaber et al. Smith and Hollander first characterised this isotope in 1955 but incorrectly assigned the mass number as 187 ( 35). Other reported values are 2.6 hours by Malysheva et al. The half-life, determined by Graeffe at 20 minutes, was confirmed by Siivola in 1966 ( 22).
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in 1980 ( 45, 46).Īlpha energy only, the half-life was measured by Cabot et al. in 1981 ( 45).Īlpha energy only, the half-life was measured by Enge et al. in 1996 ( 25).Īlpha energy only, the half-life was measured by Della Negra et al. The actual methods for the production and identification of the isotopes are given in the original reports and summarised in the Table of The Discoverers of the Platinum Isotopes.Īlpha energy only, the half-life was measured by Bingham et al. This work is connected with experiments which are searching for the proton emitting isotope 164Ir. The latest research to take place will be looking for the isotope 165Pt, which is likely to decay by alpha emission. More recently work has been concentrated on discovering the light isotopes and although such isotopes have half-lives in the millisecond region they are all alpha emitters, so that for platinum the proton drip line (see Appendix) has not yet been crossed. University of Chicago, courtesy of AIP Emilio Segrè Visual Archives Dempster was Professor of Physics at the University of Chicago Between 19 he is credited with the discovery or co-discovery of forty-five naturally occurring isotopes of nineteen elements. He developed the double focusing mass spectrograph in 1935 and used it to make the first isotopic analyses of platinum, iridium, palladium and gold. physicist Arthur Dempster joined the faculty of the Department of Physics at the University of Chicago, Illinois, in 1919. He also confirmed three others which had been discovered by Graeffe in 1963 at the University of Helsinki ( 23). In 1966, the Finnish physicist, Antti Siivola, working at the Lawrence Radiation Laboratory, University of California, announced the production and identification of nine new isotopes of platinum ( 22). The major period of discovery was, however, in the 1960s when sixteen new isotopes were announced.
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Although both set of claims were initially tentative, the two teams of claimants have subsequently been credited with the discovery of this isotope in the “Table of Isotopes” ( 1– 8). This was also chemically identified as platinum and assigned to 197Pt. They used chemical means to identify the isotope as platinum and assigned it to the ‘missing’ 197Pt.Ī year later, McMillan, Kamen and Ruben ( 21) at the same Department of Physics produced an isotope which had a half-life of 18 hours. The first definite identification of a radioactive platinum isotope was probably in 1936 by Cork and Lawrence ( 20) in the Department of Physics of the University of California who produced an isotope with a half-life of 14.5 hours. However, the mass numbers could only be guessed at until later in the same year when Dempster identified the major naturally occurring isotopes using his new type of mass spectrograph. In 1935, the possible existence of radioactive platinum isotopes was inferred by McLennan, Grimmett and Read ( 18) at the Radium Institute, London, and also by Amaldi and colleagues ( 19) in the Physics Laboratory at the University of Rome by slow neutron bombardment of the metal. The half-life of 190Pt is currently accepted as 6.5 × 10” years (650 Gy) ( 17). The rare isotope, 190Pt, was identified by Duckworth, Black and Woodcock ( 15) at the Wesleyan University, Middletown, Connecticut, in 1949 using the mass spectrographic technique and was shown to be radioactive by Porschén and Riezler in 1954 ( 16). An earlier attempt by Venkatesachar and Sibaiya to use this technique for platinum led to a misidentification of the mass numbers of the major isotopes ( 14). The actual isotopic abundances were measured using the same technique by Sampson and Bleakney in 1936 ( 11), although earlier in the same year Jaeckel and Kopfermann ( 12) and Kopfermann and Krebs ( 13) had obtained reasonable estimates of the relative isotopic ratios of the four major isotopes (the last four) by a study of the hyperfine structure of the neutral platinum spectra. Of these, the five major isotopes were discovered by Dempster at the University of Chicago, Illinois, in 1935 using a new type of mass spectrograph however, he only identified the mass numbers ( 10). The Naturally Occurring Isotopes of Platinum