Transcript
![Page 1: Photoionization and Recombinationeldora.as.arizona.edu/~yshirley/Arizona/AST300B/AST300B...Figure 13.1 Photoionization cross sections for H, H2, He. C, and O. The dashed line in (a)](https://reader033.vdocuments.us/reader033/viewer/2022043004/5f8868d914dfe4457a550d12/html5/thumbnails/1.jpg)
Photoionization and Recombination
Photoionization X + hnà X+ + e-
Radiative recombination X+ + e- à X + hn
![Page 2: Photoionization and Recombinationeldora.as.arizona.edu/~yshirley/Arizona/AST300B/AST300B...Figure 13.1 Photoionization cross sections for H, H2, He. C, and O. The dashed line in (a)](https://reader033.vdocuments.us/reader033/viewer/2022043004/5f8868d914dfe4457a550d12/html5/thumbnails/2.jpg)
2/23/19
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HII region Planetary Nebula
![Page 3: Photoionization and Recombinationeldora.as.arizona.edu/~yshirley/Arizona/AST300B/AST300B...Figure 13.1 Photoionization cross sections for H, H2, He. C, and O. The dashed line in (a)](https://reader033.vdocuments.us/reader033/viewer/2022043004/5f8868d914dfe4457a550d12/html5/thumbnails/3.jpg)
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
![Page 4: Photoionization and Recombinationeldora.as.arizona.edu/~yshirley/Arizona/AST300B/AST300B...Figure 13.1 Photoionization cross sections for H, H2, He. C, and O. The dashed line in (a)](https://reader033.vdocuments.us/reader033/viewer/2022043004/5f8868d914dfe4457a550d12/html5/thumbnails/4.jpg)
Photoionization Cross-sectionPh
otoi
oniza
tion
Cros
s-se
ctio
n 10
-18
cm2
s ~ E-3
s0 = 6.304 x 10-18 cm2
![Page 5: Photoionization and Recombinationeldora.as.arizona.edu/~yshirley/Arizona/AST300B/AST300B...Figure 13.1 Photoionization cross sections for H, H2, He. C, and O. The dashed line in (a)](https://reader033.vdocuments.us/reader033/viewer/2022043004/5f8868d914dfe4457a550d12/html5/thumbnails/5.jpg)
Ionizing Properties of Massive Stars
![Page 6: Photoionization and Recombinationeldora.as.arizona.edu/~yshirley/Arizona/AST300B/AST300B...Figure 13.1 Photoionization cross sections for H, H2, He. C, and O. The dashed line in (a)](https://reader033.vdocuments.us/reader033/viewer/2022043004/5f8868d914dfe4457a550d12/html5/thumbnails/6.jpg)