AW: CAN CHEMICAL ENVIRONMENT AFFECT NUCLEAR PROPERTIES?

[Franz Schönhofer <franz.schoenhofer@CHELLO.AT>]

Franz Schoenhofer

PhD, MR iR

Habicherg. 31/7

A-1160 Vienna

AUSTRIA

phone -43-0699-1168-1319



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--



I am happy to say that I found my "Friedlander-Kennedy". It is a

translation (1962) of the fourth edition (1960) of "Nuclear and

Radiochemistry", John Wiley and Sons, Inc., New York.



It states on p.145: "... it should be possible to change the half-life

for an electron-capture process by chemical changes, which change the

electron density close to the nucleus. E. Segré and others have shown,

that this effect exists for Be-7, which decays by electron capture with

a half-life of 54 days; the half-life is for BeF2 0.08 percent longer

than for Be-metal." A footnote mentions a similar behaviour for the

isomeric transition of Tc-99m. The original literature has not been

cited, so I cannot tell about the time this was stated, but that it must

have been for more than 45 years is rather evident!



Nevertheless the approach mentioned below and the record of almost 1%

half-life change are interesting. 



Best regards,



Franz



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









> -----Ursprüngliche Nachricht-----

> Von: owner-radsafe@list.vanderbilt.edu [mailto:owner-

> radsafe@list.vanderbilt.edu] Im Auftrag von John Jacobus

> Gesendet: Freitag, 10. September 2004 23:32

> An: radsafe; know_nukes

> Betreff: CAN CHEMICAL ENVIRONMENT AFFECT NUCLEAR PROPERTIES?

> 

> I saw this through another e-mail server and thought

> it would be of interest.

> 

> 

> PHYSICS NEWS UPDATE

> The American Institute of Physics Bulletin of Physics

> News

> Number 700 September 10, 2004  by Phillip F. Schewe

> and Ben Stein

> 

> . . .

> CAN CHEMICAL ENVIRONMENT AFFECT NUCLEAR PROPERTIES?  A

> new experiment shows that the decay lifetime of

> radioactive beryllium-7 changes by almost 1% when

> placed inside a carbon-60 molecule.  This is perhaps

> the largest shift yet seen in a chemically induced

> modification of a nuclear lifetime.   The Be-7 is

> unstable and one way for it to decay is for the

> nucleus to capture one of its own electrons, process

> in which a proton is turned into a neutron. Now if the

> Be atom lies in the cavity within a C60 molecule (in

> which case it is referred to as endohedral Be, or

> abbreviated further, Be@C60) the surrounding halo of

> carbon-based electrons apparently modifies the

> wave-functions of the beryllium-associated electrons

> and the associated "phase space" so that the rate at

> which electrons are captured by the Be nucleus  is

> speeded up.  Previous attempts to modify nuclear

> lifetimes through chemical means have resulted in

> shifts that were at the 0.15% level.  The researchers

> from Tohoku University and Yokohama National

> University (Japan) doing the present experiment

> believe that it would be premature to suggest that

> this approach can be used to mitigate the problems of

> storing radioactive materials, but, in the near term

> the use of endohedral fullerenes (cargo-carrying C60

> molecules) might lead to specialized radio-therapies

> or tracers for tagging metabolic pathways in the body.

>  (Ohtsuki et al., Physical Review Letters, 10

> September 2004; Ohtsuki@LNS.tohoku.ac.jp)

> . . .





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