Date post: | 31-Dec-2015 |
Category: |
Documents |
Upload: | melvin-gray |
View: | 33 times |
Download: | 0 times |
1
Absorption Cross Sections(Mihalas Chapter 4)
Bound-bound transitions(Einstein relations)
Bound-free transitions(Einstein-Milne relations)
2
Bound-Bound Transitions
• Balance transitions between two levels
• Upwards absorption• Downwards by
spontaneous or stimulated emission
j
i
hνij
4
Return Rates: Aji=Einstein coeff. spontaneous em. Bji=Einstein coeff. stimulated em.
(isotropic)
(same direction as Iν)
12
Einstein-Milne Relations:energy and velocity
h d mV dV Replace v dv increment in recombination term with this.
14
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. ……