Phonon neutron scattering

In summary, the conversation discusses the inference of the dispersion curve for a monoatomic 1-D chain of atoms through neutron scattering. It is explained that in one dimension, the conservation of momentum dictates a formula for the phonon momentum vector, which leads to a different omega value than the usual dispersion relation for the acoustic branch. The question is then raised about what went wrong with this formula. The answer is given that the scattering process involves conservation of both energy and momentum, and that neutron diffraction studies can be used to independently scan the momentum and energy change of the neutrons.
  • #1
gheremond
7
0
Consider a monoatomic 1-D chain of atoms (only acoustic branch). What happens with the inference of the dispersion curve through neutron scattering? In one dimension, conservation of momentum dictates $$ k'=k+K_s $$, if k_s is the phonon momentum vector and we only consider processes where a phonon is absorbed by the neutron. The corresponding omega you get from conservation of energy is thus $$ \omega = \frac{\hbar}{2 m_n} (2 k K_s+K^2_s) $$, at odds with the usual dispersion relation for the acoustic branch. What went wrong?
 
  • #3
How exactly did you get this formula?
gheremond said:
ω=ℏ2mn(2kKs+K2s)
Scattering process involves conservation of both: energy and momentum.
Neutron diffraction studies of phonons use triple axis spectrometer where you can scan the momentum and energy change of the neutrons independently.
 

What is phonon neutron scattering?

Phonon neutron scattering is a type of experimental technique used in materials science and condensed matter physics to study the lattice vibrations, or phonons, of a material by scattering neutrons off of its atomic nuclei.

How does phonon neutron scattering work?

In phonon neutron scattering, a beam of neutrons is directed at a sample of the material being studied. As the neutrons interact with the atomic nuclei, they are scattered in different directions and their energy is changed. By analyzing the scattered neutrons, scientists can learn about the phonon modes and energy levels of the material.

What can be learned from phonon neutron scattering experiments?

Phonon neutron scattering experiments can provide information about the vibrational frequencies and energy levels of a material, as well as the interactions between atoms in the material. This can help scientists understand the thermal and mechanical properties of a material, as well as its electronic and magnetic properties.

What types of materials can be studied using phonon neutron scattering?

Phonon neutron scattering can be used to study a wide range of materials, including metals, semiconductors, insulators, and magnetic materials. It is particularly useful for studying materials with complex crystal structures or materials with low atomic number elements, such as hydrogen or lithium.

What are the advantages of using phonon neutron scattering?

Phonon neutron scattering has several advantages over other experimental techniques for studying lattice vibrations. It is non-destructive, meaning the sample is not altered during the experiment. It is also sensitive to a wide range of frequencies, making it useful for studying both high- and low-energy phonons. Additionally, it can provide information about the momentum transfer between atoms during vibrations, giving a more complete picture of the material's properties.

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