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Absorption Cross Sections (Mihalas Chapter 4). Bound-bound transitions (Einstein relations) Bound-free transitions (Einstein-Milne relations). Bound-Bound Transitions. Balance transitions between two levels Upwards absorption Downwards by spontaneous or stimulated emission. j. h ν ij. i. - PowerPoint PPT Presentation
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Absorption Cross Sections(Mihalas Chapter 4)
Bound-bound transitions(Einstein relations)
Bound-free transitions(Einstein-Milne relations)
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Bound-Bound Transitions
• Balance transitions between two levels
• Upwards absorption• Downwards by
spontaneous or stimulated emission
j
i
hνij
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Return Rates: Aji=Einstein coeff. spontaneous em. Bji=Einstein coeff. stimulated em.
(isotropic)
(same direction as Iν)
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Einstein-Milne Relations:energy and velocity
h d mV dV Replace v dv increment in recombination term with this.
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Denominator Term:Maxwell dist. ne(v); Saha eq. n0/n1
ng
g
h
m kTe e p m
nm
kTe v hG v
g h p
g m v G ve
e
h
kT
m v
kTv
e
m v
kT
h
kT
0
1
2 3 2
2
3 2
2 2
02
12 2
2 2
24
1
2 41
2
2
/
/
…….=1. ……