next up previous contents
Next: Collisional Excitation and Deexcitation Up: Einstein's Coefficients Previous: Absorption   Contents


Induced Emission

When atoms in the state n$_u$ are in the radiation field with the average intensity of $J_{n_u\rightarrow n}$, downward transition from n$_u$ to n is induced and atoms emit photons with energy $h\nu_{n_u\rightarrow n}$. This is called the induced emission or stimulated emission. This rate is expressed as
\begin{displaymath}
B_{n_u\rightarrow n}J_{n_u\rightarrow n}N_{n_u}.
\end{displaymath} (2.136)



Kohji Tomisaka 2007-07-08