Other Methods of Creating A Population Inversion
Stimulated emission was first observed in the microwave region of the electromagnetic spectrum, giving rise to the acronym MASER for Microwave Amplification by Stimulated Emission of Radiation. In the microwave region, the Boltzmann distribution of molecules among energy states is such that, at room temperature all states are populated almost equally.
To create a population inversion under these conditions, it is necessary to selectively remove some atoms or molecules from the system based on differences in properties. For instance, in a hydrogen Maser, the well-known "21cm wave" transition in atomic hydrogen, where the lone electron flips its spin state from parallel to the nuclear spin to antiparallel, can be used to create a population inversion because the parallel state has a magnetic moment and the antiparallel state does not. A strong inhomogeneous magnetic field will separate out atoms in the higher energy state from a beam of mixed state atoms. The separated population represents a population inversion which can exhibit stimulated emissions.
Read more about this topic: Population Inversion
Famous quotes containing the words methods, creating and/or population:
“We can best help you to prevent war not by repeating your words and following your methods but by finding new words and creating new methods.”
—Virginia Woolf (1882–1941)
“If the child knows the rewards and punishments in advance and knows that his parents will stick to them, the parents can actually empathize with the child’s plight while, at the same time, creating a firm sense of structure.... Your child will sense your resolve and your empathywhether you do this with words or just a sense of warmth.”
—Stanley I. Greenspan (20th century)
“[Madness] is the jail we could all end up in. And we know it. And watch our step. For a lifetime. We behave. A fantastic and entire system of social control, by the threat of example as effective over the general population as detention centers in dictatorships, the image of the madhouse floats through every mind for the course of its lifetime.”
—Kate Millett (b. 1934)