• A 36Cl Profile in Greenland Ice from AD 1265 to 1865

      Conard, N. J.; Gove, H. E.; Elmore, David (Department of Geosciences, The University of Arizona, 1989-01-01)
      We have measured the concentration of 36Cl in 67 samples from the upper portion of the Camp Century ice core. The profile extends from AD 1265 to 1865 and covers the times of the Wolf (AD 1282-1342), Spoerer (AD 1416-1534) and Maunder (AD 1645-1715) minima in sunspot number. Although the profile exhibits much short-term variation, a smoothed plot of the data shows a strong peak in 36Cl concentration over the time of the Maunder Minimum. The deeper part of the core suggests increased deposition of 36Cl over the periods of the Wolf and Spoerer minima. The time resolution of the profile is inadequate for testing for an 11-year periodicity in our data. The data augment evidence from 10Be and 14C studies which indicate solar modulation of radioisotope production. Since, however, much of the short-term variation of 36Cl seems to be independent of solar activity, other factors must affect the deposition of 36Cl in ice. These variations could be due in part to mechanisms affecting the transport of 36Cl in the atmosphere. Based on our data from Camp Century, we calculate an average input of 36Cl of 24 atoms/m2 sec.
    • AMS of 41Ca Using the CaF3 Negative Ion

      Kubick, Peter W.; Elmore, David (Department of Geosciences, The University of Arizona, 1989-01-01)
    • Depth Profiles of Nitrogen and Chlorine in Pure Materials Through AMS of the Neutron Activation Products 14C and 36Cl

      Elmore, David; Hossain, T. Z.; Gove, H. E.; Hemmick, T. K.; Kubik, P. W.; Jiang, Songsheng; Lavine, J. P.; Lee, S. T. (Department of Geosciences, The University of Arizona, 1989-01-01)
      Determination of the more common light elements such as nitrogen and chlorine at trace levels is difficult because of their high abundance on sample surfaces, in materials used to build analysis instruments, and in the residual gas of the instrument vacuum. We present here a new approach to analysis of these elements: accelerator mass spectrometry (AMS) combined with neutron activation. The problem of contamination is overcome by using neutron activation to produce long-lived radioisotopes which generally have low concentrations in the environment. For measurement of 14N and 35Cl, AMS can provide sensitive background-free measurements of their neutron activation products 14C and 36Cl and, in addition, can provide depth profiles. These are the first results of this new method: depth profiles of nitrogen and chlorine implanted in semiconductor grade silicon.