Electrons from Internal Conversion

[Zuzana]

Hi,
I would like to ask, why K-shell electrons coming from the internal conversion are much more frequent than L or M-shell electrons (see Fig). K-shell electrons are more tightly bound than L-shell, I would say that it is easier for gamma particle to kick off less tightly electron, no?

Thank you in advance for the reply.

 

[DrClaude]

The probability of an electron being found within the nucleus decreases as the shell increases. It is more probable for a K electron to be involved in the internal conversion process than an L or M electron.

 

[Zuzana]

The probability of an electron being found within the nucleus decreases as the shell increases. It is more probable for a K electron to be involved in the internal conversion process than an L or M electron.

what do you mean by "within the nucleus"? electrons are at the atomic orbitals (shells outside the nucleus).

 

[DrClaude]

what do you mean by "within the nucleus"? electrons are at the atomic orbitals (shells outside the nucleus).

No, the wave function is extended. There is a non-zero probability of finding the electron at the nucleus.

 

[jtbell]

Aha, DrClaude beat me to it while I was Googling. Here's another set of examples:

http://hyperphysics.phy-astr.gsu.edu/hbase/hydwf.html

The probability of the electron having a small-enough value of $r$ to be inside the nucleus, is smaller for excited states (e.g. L-shell i.e. 2s, 2p) than for the ground state (K-shell i.e. 1s).

 

[Zuzana]

Now, I understand. Thanks a lot for the reply.

 

[jtbell]

On the graphs at the link that I posted, the horizontal axis is given as multiples of $a_0$, the Bohr radius (the radius of the K shell in the Bohr model).

Exercise: look up typical values for the radius of nuclei that undergo internal conversion, and compare to $a_0$, so as to see what part of those graphs comes into play in internal conversion.