Bulletin #16                                      September 25, 2001

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                 ATOMIC        MASS        DATA       CENTER

    --------------------------------------------------------------------

    I - NEWS FROM EXPERIMENTS ON MASSES

    Mass mapping of n-def sub-U nuclides / Yu.N. Novikov  September 2001

    The masses of 64 short-lived neutron-deficient nuclides covering the
    element  range  from  tungsten to uranium have been obtained for the
    first  time. They have been evaluated by combining directly measured
    masses  from  Schottky  Mass  Spectrometry  with linked experimental
    Qalpha-values  in  a-decay  chains.  Based on these new mass data we
    have  determined the one-proton and two-proton drip-lines as well as
    the  size  of the ``littoral shallow'' of the sea of instability. No
    evidence  of  a  Thomas-Ehrman shift has been found in the region of
    the  investigated  heavy nuclides. A peculiar behavior of two-proton
    separation  energies  has  been  observed  in  the  lead region. The
    predictive power of various mass models is investigated.

    The  preprint  of  the  submitted  paper is available from the AMDC:
    http://csnwww.in2p3.fr/AMDC/experimental/novikov.pdf


    Mistral measurement of Mg isotopes   /   Dave Lunney  September 2001

    Last  week,  the  MISTRAL  experiment  at  ISOLDE/CERN  had  a  very
    successful run, measuring masses of exotic neutron-rich Mg isotopes.

    Back  in 1999, MISTRAL had its first run using the ISOLDE hot plasma
    ion   source.   Due  to  overwhelming  isobaric  contamination,  the
    measurements  were  compromised due to the very high resolving power
    that  was  needed  to  obtain a clean mass peak. The result was that
    only  one  isotope,  32Mg  (in  addition  to  two  Ne isotopes), was
    measured (see http://csnwww.in2p3.fr/AMDC/experimental/apac-srf.pdf)

    This  time  the  chemically  selective  laser  ion  source  was used
    (cf. http://isolde.web.cern.ch/ISOLDE/normal/laseions.html).     Not
    only  did  the  suppression  of  isobaric  background  allow  higher
    transmission (due to lowered required mass resolution) but the laser
    ionization  was  inherently more efficient. This allowed us not only
    to  confirm  and improve our previous, the low-statistic, mass value
    for 32Mg, but also to obtain a new value for 33Mg. Additionally, the
    masses  of  29,30,31Mg were improved. These nuclides have half-lives
    ranging from 1.3 s down to 90 ms.


    II - GENERAL INFORMATION

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    Address:   Atomic  Mass  Data  Center
               C.S.N.S.M. (IN2P3-CNRS)
               Batiment 108
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