ethan@utastro.UUCP (Ethan Vishniac) (10/21/85)
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The trouble with graduate students is that they`re too smart.
OK I said that restricting the phase space of decay products was
the only way to change decay rates through the environment.
One Jeff Brown (stand up and bow Jeff) gently reminded me that
many radioactice nucleii have metastable excited states with
different decay channels than the ground state. In other words,
in a sufficiently energetic plasma you can jiggle the nucleii
and persuade them to decay faster. Typical energies required
are about a few Mev or temperatures of about a billion degrees
absolute. I'm not a nuclear physicist, but I suspect there
are nucleii where states exist that are almost degenerate with
the ground state and require smaller temperatures to excite.
I couldn't say which common radioactive atoms might have these
states.
--
"Superior firepower is an Ethan Vishniac
important asset when {charm,ut-sally,ut-ngp,noao}!utastro!ethan
entering into ethan@astro.UTEXAS.EDU
negotiations" Department of Astronomy
University of Texasgwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>) (10/22/85)
I don't know about affecting the decay RATE as such, but a powerful technique for investigating magnetic critical point behavior is to dope the sample with an isotope that decays via a pair of oppositely directed gammas, and put the sample in an aligning magnetic field with gamma detectors around the setup. By studying the gamma-gamma correlations one can infer the magnetic field near the probe nuclei. (This technique is called "Perturbed Angular Correlation"; it was a specialty of CLark University not very many years ago.) Temperature effects are quite evident in this experiment, so temperature can have detectable effects on nuclear decay.
ethan@utastro.UUCP (Ethan Vishniac) (10/22/85)
> I don't know about affecting the decay RATE as such, > but a powerful technique for investigating magnetic > critical point behavior is to dope the sample with > an isotope that decays via a pair of oppositely > directed gammas, and put the sample in an aligning > magnetic field with gamma detectors around the setup. > By studying the gamma-gamma correlations one can > infer the magnetic field near the probe nuclei. > (This technique is called "Perturbed Angular > Correlation"; it was a specialty of CLark University > not very many years ago.) Temperature effects are > quite evident in this experiment, so temperature can > have detectable effects on nuclear decay. Hmm... I have a question about this. It seems clear that the correlations are produced by correlations between the direction of emission and the direction of the magnetic moment of the nucleus. Wouldn`t the temperature effects be due not to changes in the decay rate but from fluctuations in the alignment of the nucleii with the external field? Not afraid to show my ignorance. -- "Superior firepower is an Ethan Vishniac important asset when {charm,ut-sally,ut-ngp,noao}!utastro!ethan entering into ethan@astro.UTEXAS.EDU negotiations" Department of Astronomy University of Texas
gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>) (10/23/85)
> > I don't know about affecting the decay RATE as such, > > ... so temperature can > > have detectable effects on nuclear decay. > Hmm... I have a question about this. It seems > clear that the correlations are produced by correlations > between the direction of emission and the direction of the > magnetic moment of the nucleus. Wouldn`t the temperature > effects be due not to changes in the decay rate but from > fluctuations in the alignment of the nucleii with the external > field? Yes, the H-dot-S effect. I was careful to say this wasn't the decay RATE.