An isomeric transition is a nuclear process in which a nucleus with excess energy following the emission of an alpha particle or a beta particle emits energy without changing its number of protons or neutrons.
After a radioactive nucleus undergoes an isobaric transition (beta emission, positron emission, or electron capture), it usually contains too much energy to be in its final stable or daughter state. Nuclei in these intermediate and final states are isomers, since they have the same atomic and mass numbers. Nuclei in the intermediate state will undergo an isomeric transition by emitting energy and dropping to the ground state.
An isomer of a molecule has the same number of atoms of each element, but has a different arrangement of the atoms. It has the same molecular formula as the other molecule, but with a different chemical structure.
Stereoisomers are isomeric molecules that have the same molecular formula and sequence of bonded atoms (constitution), but differ in the three-dimensional orientations of their atoms in space.
Optical isomerism is one form of stereoisomerism. Optical isomerism. Why optical isomers? Optical isomers are named like this because of their effect on plane polarised light.
PLANE POLARISED LIGHT
A simple explanation of what plane polarised light is and the way it is affected by optically active compounds.
A simple analogy - ‘plane polarised string’
Imagine tying a piece of thick string to a hook in a wall, and then shaking the string vigorously. The string will be vibrating in all possible directions, up-and-down, side-to-side, and all the directions in-between, giving it a really complex overall motion.
Now, suppose you passed the string through a vertical slit. The string is a really snug fit in the slit. The only vibrations still happening the other side of the slit will be vertical ones. All the others will have been prevented by the slit.
What emerges from the slit could be described as ‘plane polarised string’, because the vibrations are only in a single (vertical) plane.
Now look at the possibility of putting a second slit on the string. If it is aligned the same way as the first one, the vibrations will still get through.
But if the second slit is at 90° to the first one, the string will stop vibrating entirely to the right of the second slit. The second slit will only let through horizontal vibrations, and there aren't any.
Plane polarised light
Light is also made up of vibrations, this time, electromagnetic ones. Some materials have the ability to screen out all the vibrations apart from those in one plane and so produce plane polarised light.
The most familiar example of this is the material that Polaroid sunglasses are made of.
Mirror.... In chemistry, an enantiomer, also known as an optical isomer, is one of two stereoisomers that are mirror images of each other that are non-superposable, much as one's left and right hands are the same except for being reversed along one axis.
Particularly used in clinical pharmacology (there is a proven medical purpose), in drug/medicine making.
A mirror neuron is a neuron that fires both when an animal acts and when the animal observes the same action performed by another. Thus, the neuron ‘mirrors’ the behaviour of the other, as though the observer were itself acting.
This is a playful experiment in manipulating brain chemistry through art.
Edited text and technical images from: Deranged Physiology & ChemGuide.