At 07:22 PM 5/6/2010, mix...@bigpond.com wrote:
The problem I have with Takahashi is that Be8 is itself unstable, with a very
short half life. Therefore, I would expect
excited state Be8 to have a very much
shorter half life, particularly given the huge amount of energy available
compared to that available in ground state Be8[1]. Consequently I wonder where
it finds the time to radiate energy to the
environment before breaking into two
alphas. It seems to me that breaking into two alphas would be the preferred
means of de-excitation, and I would expect it to
occur at least 99% of the time,
before any energy was radiated.
Well, don't ask me! Yes, the half-life of Be-8 is
short, but I don't know how nuclear excitation will affect the half-life.
[1] The difference in energy between ground state Be8 and 2 He4 nuclei is just
91 keV, yet even this is sufficient to ensure that the half life of Be8 is on
the order of 1E-16 sec.
Wikipedia, that fountain of accurate information,
gives 6.7(17)×10-17 seconds, about what you said.
At 47.6 MeV it should be on the order of 1E-23 sec.
How did you determine that?
In
that time, light can only travel about 4 fm, which gives it no opportunity to
communicate with the rest of the lattice.
To dump the energy, the photons must be emitted
from the nucleus. Reaching the lattice would not
matter. The atomic radius of Be-8 would be, I think, about 3 fm. Close.
The generated Be-8 would have low momentum with
respect to the metal lattice, it would be bound
to it until it decays. I don't know if this would
have any effect at all on stability, and I don't
know the rate at which photon emission, which is
down through a series of excitation levels, would
take place. Takahashi did discuss it, but only a
little, at one point. My suspicion: nobody knows
what happens when a BEC condensate fuses. Maybe
the electrons fly off with the energy. But that
would also generate visible effects, I believe,
though they wouldn't get far, if I'm correct.
It's somewhat the same problem with the alphas.
If Hagelstein is correct, 91 KeV is still too much.
