ess.spectroscopy.indirect.conversion.lab_momentum_transfer_from_incident_energy#

ess.spectroscopy.indirect.conversion.lab_momentum_transfer_from_incident_energy(incident_energy, incident_beam, final_wavevector)[source]#

Compute the momentum transfer in the lab frame.

Here, the momentum transfer is defined as

\[\vec{Q} = \vec{k_i} - \vec{k_f}\]

with

\[\vec{k_i} = \frac{2\pi}{h} \hat{b}_i \sqrt{2 M_n E_i}\]
Parameters:

  • incident_energy (Variable) – The neutron energy \(E_i\) before scattering.

  • incident_beam (Variable) – The vector of the incident beam in the lab frame \(\vec{b}_i\).

  • final_wavevector (Variable) – The neutron wavevector \(\vec{k_f}\) after scattering.

Returns:

Variable – The momentum transfer \(\vec{Q}\) in the lab frame.