Relation of EM radiation equation to radioactive decay

[zgoddard3]

Hello,

I am a Mechanical Engineering student but I am a TA for an electricity and magnetism course, and I had a student ask a question that's a little bit outside my understanding. The question was related to the equation for a radiating electric field from an accelerating charged particle:

E_rad = 1/(4πε₀) * -qa_⊥/c²r

This is an equation we always teach at the end of the course, but never go into much detail on it, and I myself have never really explored it much further.

The question my student asked was how this equation relates to radiation from radioactive elements. For alpha and beta radiation my answer was that they would not be related, since they are particles with mass, and not EM radiation. For gamma radiation, I was less sure. I remember from chemistry that excited electrons release a photon when falling back to a lower energy level. I was thinking that when the electron changes orbit it would have a sudden change in velocity causing the release of the EM wave. Is this on the right track and would anyone have a good answer that I could give to my student and future students who might have the same question?

 

[kuruman]

Accelerated charges generate EM radiation, a.k.a. photons. Radioactive decay produces alpha "radiation" (Helium nuclei), beta "radiation" (electrons and positrons), gamma "radiation" (photons) and neutrino "radiation". The EM radiation that is emitted when electrons jump to a lower orbit is not considered radioactivity as the aforementioned products of radioactive decay emanate from the nucleus.

 

[zgoddard3]

For alpha and beta radiation, that is what I thought. But gamma radiation is part of the electromagnetic spectrum, right? So where does it come from during radioactive decay?

A brief search seemed to indicate that gamma radiation during radioactive decay can come from the nucleus or orbiting electrons. For emission from electrons I figured that could be from a change in the orbit or that the gamma radiation could be released with a beta particle, since that electron would also undergo acceleration.

For gamma radiation from the nucleus, all I've found so far is that the gamma radiation is released to bring the nucleus from a higher energy state to a lower energy state, which sounds similar to a electron emitting a photon when moving from one energy level to the next. My question there is what signifies a higher energy state in a nucleus and how does it transition back to a lower energy state?

 

[kuruman]

My question there is what signifies a higher energy state in a nucleus and how does it transition back to a lower energy state?

As a starter, you may find these URLs informative.
http://hyperphysics.phy-astr.gsu.edu/hbase/Nuclear/shell.html
http://www2.lbl.gov/abc/wallchart/teachersguide/pdf/Chap06.pdf