Eric etal--
I have always thought that the so called branching ratios were associated with
potential states of the system that conserve linear momentum and angular
momentum of the earlier system that is subject to decay. With the interaction
of particles with linear momentum something has to be produced that conserves
this momentum and yet is an allowed energy state in the new system.
If large angular momentum is involved in the initial state, the decay state
must be able to conserve that angular momentum. In varying magnetic fields
variations in allowed spin energy states occurs and hence the allowed angular
momentum of the system also changes. If it is possible to match the new system
angular momentum with the initial system's angular momentum, but at a lower
total energy, it is possible that mass loss will occur with the exit of energy
to the environment of the new system.
If spin coupling (transfer of angular momentum ability) between the new system
and its environment exists, then angular momentum need not be conserved
between the initial system and the new system. Such coupling may very well
change the decay ratios that Eric is thinking about, much the same way he is
thinking about charge density changing the ratios.
Bob
----- Original Message -----
From: Eric Walker
To: vortex-l@eskimo.com
Sent: Sunday, February 01, 2015 1:28 PM
Subject: Re: [Vo]:earlier thread on surface vs volume effect in the gamma
decay of radioisotopes
On Sun, Feb 1, 2015 at 12:49 PM, <mix...@bigpond.com> wrote:
It must be one of the thousands that I deleted unread, however I wouldn't
expect
that sort of thing to affect gamma radiation.
Maybe. But consider for a moment the decay of a [dd]* compound nucleus,
which normally follows one of the two strong-interaction branches, where it
breaks up, and very occasionally follows the EM branch, in which a gamma is
emitted after a long period of time. Typically, I believe, such decays are
measured in ion bombardment experiments or in dusty plasmas and the branching
ratios are inferred from results obtained in such contexts.
In the ion bombardment experiments, I assume the incoming d+ ion encounters
the d atom embedded within the metal, but in a region of little charge density,
and you get the usual branching ratios. (Or perhaps experimentalists work
backwards from their results, assuming the normal branching ratios.)
Suppose for a moment that the electron charge density had an effect on the
branching ratios. If the charge density is high, the supposition is that the
EM transition is heavily favored for [dd]* decay, but the momentum is shared
with one or more electrons, so that you do not get a gamma, but instead one or
more energetic electrons. A problem with this thought experiment is that it
does not explain why gammas are seen in the decays of radioisotopes with gamma
branches; presumably if electron charge density had an effect, you would not
see sharp gammas peaks for such radioisotopes but instead energetic electrons
and associated continuum radiation.
Here a counterargument to the electron charge density hypothesis is that if
charge density was a factor, you might expect to see a volume/surface effect.
The more surface area, presumably the lower the charge density at the surface,
and hence more gamma activity from the radioisotope. The argument is that this
kind of volume versus surface effect is not observed, so the hypothesis needs
to be revisited.
The thought that I had to add to this discussion is that there need not be a
surface-volume effect for the charge density hypothesis to remain a
possibility. Even if the gamma emitting radioisotope is embedded deep within a
solid, I assume the net charge around the nucleons will be positive. By
contrast, if a [dd]* compound nucleus were decaying within the dense electron
cloud of a metal, it might be straightforward for the surrounding electrons to
overwhelm the 2+ charge from the two protons, leading to a net negative charge
density, even within the field of the [dd]* nucleus.
Eric
