Slide 3
Slide 3 text
EXAFS Equation
Here’s the EXAFS equation:
χ(k, Γ) =
(NΓ
S2
0
)FΓ
(k)e−2σ2
Γ
k2
e−2RΓ/λ(k)
2 kR2
Γ
sin (2kRΓ
+ ΦΓ
(k)) (1)
χtheory
(k) =
Γ
χ(k, Γ) (2)
RΓ
= R0,Γ
+ ∆RΓ
(3)
k = 2me
(E0 − ∆E0
)/ 2 ≈ (E0 − ∆E0
)/3.81 (4)
The oscillatory term is a function not of 2kR, but of 2kR + Φ(k).
The integral that makes ˜
χ(R) is usually done over 2k, i.e.
˜
χ(R) = d(2k) kkw · χ(k). This makes ˜
χ(R) look somewhat like a radial
distribution function with peaks near sensible values of R (half-path-length),
rather than 2R (full-path-length).
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EXAFS Phase Shifts