photoionization and recombinationeldora.as.arizona.edu/~yshirley/arizona/ast300b/ast300b...figure...
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Photoionization and Recombination
Photoionization X + hnà X+ + e-
Radiative recombination X+ + e- à X + hn
2/23/19
1
HII region Planetary Nebula
H and He Recombination Rates
Use in HII regions
Hydrogen:aA ~ 4.17x10-13 (T/104K)-0.721-0.018ln(T/104K)
aB ~ 2.59x10-13 (T/104K)-0.833-0.035ln(T/104K)
Helium:aB ~ 2.72x10-13 (T/104K)-0.789
Photoionization Cross-sectionPh
otoi
oniza
tion
Cros
s-se
ctio
n 10
-18
cm2
s ~ E-3
s0 = 6.304 x 10-18 cm2
Ionizing Properties of Massive Stars
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