## Einstein's Coefficients

In this section, we describe the absorption coefficient and the emissivity for the line emission and absorption. Here, consider a hypothetical atom which has only three levels named n, n, n. and assume the energy of each level is, respectively, , , and . When the atom changes its state from n to n, an photon with energy of is emitted, if this transition is radiative. Besides the radiative process, atom changes its state exchanging its energy with other atoms, molecules and electrons.

Subsections

Kohji Tomisaka 2009-12-10