absorption of
photon
excited
state of atom
atomic decay w/
photon emission
hn = Eupper�- Elower
3
radiative processes :
��photon absorption
��spontaneous decay w/ emission of photon
��stimulated emission
2
collisional processes:
��collisional excitation
��collisional de-excitation
D E
= Efinal�- Einitial�= hn (radiation)
, 1/2 mv2 (collisional)