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Re: Russian scientists add new element to periodic table
Dear Susan,
Thank you for bringing this item to our attention. But I must say that
I can understand why Al Ghiorso is skeptical. Projectiles such as Ca
are notoriously deficient in neutrons: Ca has mostly mass 40, and is
composed of 20 protons and 20 neutrons. This means a ratio Z/N = 1,
which is typical for low mass nuclei. Element 114, at the upper end of
the sequence of relatively stable nuclei, is likely to need a Z/N-ratio of
at least 1.5. As an example: 239Pu has 94 protons and 145 neutrons,
corresponding to a Z/N ratio of 1.54. Note that the doubly magic
element 114 with 184 neutrons and a mass number of 298 already
needs a Z/N ratio of 1.61. The excess neutrons are needed to bind
with their short-range strong force the nucleus against the powerful,
long-range electrostatic repulsion between all the protons.
This discussion reminds me of the late sixties when new theoretical
model calculations led to speculations about an island of stability
around the doubly magic isotope 298 (114,184). In the post-
doctoral process of habilitation, I studied the problem in 1968 and
gave the Faculty of Natural Sciences at the University of Basel a
talk on that island of stability, and the prospects and difficulties of
getting there. It was clearly going to be a difficult undertaking, but
even so, I was much too optimistic and said that we would get there
in a few years, much sooner than we actually did.
The difficulty is to get from Pu + Ca to Z=114. On the proton side
that is easy, as 94 + 20 is 114. The neutron numbers are quite a
bit more difficult, however. Let us take the heaviest stable Ca
isotope as projectile, and the heaviest long lived Pu isotope as a
target. This means shooting Ca-48 ions at a Pu-244 target. The
mass of the resulting 114 isotope is 292, which is deficient by 6
neutrons when compared to the mass of 298 required for maximum
theoretical stability.
This can mean only one of two things: One, the Russian data are
correct, and then the island of stability is wider and more stable than
originally estimated; or Two, the Russian data are wrong, and then,
although we may be in "shallow water" near the island, we have not
reached the shore yet. Well, as usual, time will tell.
Best regards,
Fritz
Susan Gawarecki wrote:
> Russian scientists add new element to periodic table
> ...............................
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Fritz A. Seiler, Ph.D.
Principal
Sigma Five Associates
P.O. Box 14006
Albuquerque, NM 87191-4006
Tel. 505-323-7848
Fax. 505-293-3911
e-mail: faseiler@nmia.com
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AS OF 7/22/1999 USE:
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Fritz A. Seiler, Ph.D.
Principal
Sigma Five Associates
P.O. Box 1709
Los Lunas, NM 87031
Tel. 505-866-5193
Fax. 505-866-5197
e-mail: faseiler@nmia.com
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