Questions from class - Lecture 4 Flashcards Preview

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Flashcards in Questions from class - Lecture 4 Deck (4):
1

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)

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* + ...

3

What is the Guinier approximation?

P(q) ≈ exp[-1/3 * q^2]

for qR_g < 1

4

Which regimes does a scattering curve of a single polymer feature?

Intermolecular regime, Guinier regime and the fractal regime.