Flashcards in Questions from class - Lecture 4 Deck (4)
What is the definition of the scattering vector?
The scattering vector is the difference between the incident wavevector and the scattered wavevector:
q = k_i - k_s.
For elastic scattering:
q = 4πn/lambda * sin (theta/2)
What is the form factor of a chain with a certain radius of gyration?
P(q) = 1/N^2 * ∑∑ sin(qR_ij)/qR_ij.
For small scattering angles qR_ij = qR_g, and a Taylor expansion can be used:
P(q) = 1 - 1/3*q^2* + ...
What is the Guinier approximation?
P(q) ≈ exp[-1/3 * q^2]
for qR_g < 1