absorption
of
photon
excited state of atom
atomic decay
+
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
DE = Efinal - Einitial = hn (radiation) OR = 1/2 mv2 (collisional)
® additional photon