Is radioactive decay independent of the environment?

[Schnellmann]

Main Question or Discussion Point

Is the rate of radioactive decay fixed or does the environment have any impact eg would the rate of decay be the same in a low or very high gravitational field (in both cases measured from the viewpoint of the radioactive material)?

 

[vanhees71]

In some special cases you can have huge effects. One example is bound $\beta$ decay, where the electron decays into a bound atomic state rather than a free (scattering) state. Of course it can do so only if the corresponding atomic state is not occupied by an electron since electrons are fermions. A famous example is Rh 187 which as a neutral atom decays with a half-life of about $42 \cdot 10^9 \, \text{y}$, making it apparently to a perfect clock to measure the age of astrophysical objects by measuring the abundance ratio of Rh and Os (it's decay product). However, when the Rh is ionized, then bound-state $\beta$ decay can take place. Then the half-life becomes of the order of $10 \; \text{y}$, i.e., a 9 orders of magnitude smaller value. In fact the half-life of ionized Rh 187 has been measured at GSI in Darmstadt (Germany) to be $33 \;\text{y}$. For a very nice review by Fritz Bosch, one of the scientists involved in these measurements, see

http://www.euroschoolonexoticbeams.be/site/files/nlp/LNP651_contrib5.pdf

 

[DrChinese]

Is the rate of radioactive decay fixed or does the environment have any impact eg would the rate of decay be the same in a low or very high gravitational field (in both cases measured from the viewpoint of the radioactive material)?

Gravity does affect the radioactive 1/2 life in the sense that time appears to "slow down" when enough mass is present.

 

[Vanadium 50]

In some special cases you can have huge effects.

For example, some nuclei decay by electron capture. If you are looking at fully stripped nuclei (no electrons), these decays don't happen.

 

[vanhees71]

For example, some nuclei decay by electron capture. If you are looking at fully stripped nuclei (no electrons), these decays don't happen.

Yep, that's a crossing-symmetric reaction to my example of bound $\beta$ decay :-)).