Cymric wrote:
Err. I. no. can. do. in. sim-ple. words. But I can try to do it in slightly more complex ones :-).
Haha! Will try to do my best to keep up...
All fundamental particles have a property known as spin. Spin is basically the way such a particle revolves on its axis, although you have to keep in mind that this view is a macroscopic analogue, and thus can only be taken so far before quantummechanical weirdness steps in.
Was doing fine until I stumbled across quantimmechanical weirdness... Seriously though I understand the priciple of particles revolving so far.
However, for the purposes of this discussion, it will do fine.
Am thankful for that...
It turns out that a bunch of protons, neutrons and electrons are happiest, i.e., have the lowest energy, when all spins are parallel. In other words, the particles are revolving in the same direction. Now imagine that we supply them with some energy. That can cause the spins to lose alignment and become anti-parallel. This so-called excited state is unstable: the system tries to lose the excess energy by radiating it away. That radiation can take on many forms: it can be X-rays, it can be ordinary light, it can be heat.
I see, in the case of an LED light, we supply energy which causes the structure of the filament to become excited and thus convert the energy to radiation... Hence the bright green light I see coming from the LED on my monitor. Or indeed the burst of X-ray radiation from a hospital X-ray machine.
In case of electrons, such loss of energy is quick and in almost all cases, practically instantaneous.
Swithcing off electricity supply = LED extinguishing as the source of energy exciting the molecules is removed.
Exceptions are when we are dealing with systems in vacuum (like outer space)
Because there's no conductor to aid radiation of energy?
or phosphoresence, which can last for several hours. In an atomic nucleus, it is much more difficult to get rid of the energy, as a nucleus is a rather 'fluid' entity. There is much more interaction between protons and neutrons, and that tends to stabilise matters. Sometimes to such a degree that a nucleus might exist for millions of years in its excited state before it finally radiates away the energy.
And I assume this is how radioactive metals for example remain in such a state for a substantial length of time?
Since these excited nuclei have different properties from the unexcited one, they are referred to as isomers: same mass, different properties. Such a name does not exist for excited electrons: they lose their energy too quickly.
So the large bit in the middle of the atom (nucleus) will react differently when in it's energized state to the smaller bits that go round the big bit (neutrons, electrons)?
Please excuse my use of language, I'm trying to break it down so I understand it and my fellow intellectually challenged can keep up!
What is interesting about this nuclear reorganization is that much more energy is liberated. The radiation therefore appears as gamma rays, which are much more damaging than the already potent and dangerous X-rays.
Ah! With you now! So Gamma Ray radiation is the result of a different process than other forms of radiation (x ray, infrared, heat)? I am aware that Gamma ray radiation is both difficult to shield against and causes damage to our DNA.
Now we finally come to 'isomeric triggering': you take a clump of atoms (usually a metal) in which the nuclei are known to be in their excited state. You bombard them with low energy radiation---usually X-rays---and hope that this pulse will be the tiny push the atom needs in order to flip its nuclear spins back in line, and thus produce the desired gamma radiation. In other words, you try to influence or even control the process of normal decay.
...usually in a metal? As in a piece of radiactive material? You bombard it with x ray radiation and the material suddenly (or over a certain amount of time) 'flips' to a stable state and sheds a large burst of gamma ray radiation? So you can influence the material to emit a pre-calculated burst of said gamma rays?
Needless to say, generating strong beams of gamma radiation at will can be a pretty powerful weapon. It can also be a very effective source of radiation in nuclear medicine: you just seed a tumor with tiny clumps of the material, X-ray them gently, and the tumor is killed effectively without the healthy surrounding tissue being affected too much.
So the gamma ray burst may be focused in some fashion? Is this the concept of a gamma ray beam?
