q_lab_to_tth_eta

anri.diffract.q_lab_to_tth_eta(q_lab, wavelength)

Convert from scattering vector \(\vec{Q}\) in lab frame to (tth, eta) angles.

Adapted from ImageD11.transform.uncompute_g_vectors()

Parameters:

• q_lab (Array) – [3] Scattering vector in lab frame

• wavelength (float) – wavelength, same units as q_lab

Returns:

• tth (jax.Array) – \(2\theta\) angle in degrees

• eta (jax.Array) – \(\eta\) angle in degrees

Notes

\[\begin{split}\begin{aligned} d^* &= \abs{\vec{Q}} \\ \sin{\theta} &= \frac{d^* \lambda}{2} \\ 2\theta &= 2 \arcsin\left(\frac{\abs{\vec{Q}}\lambda}{2}\right) = 2 \arcsin\left(\frac{d^* \lambda}{2}\right)\\ \eta &= \arctan2\left(-Q_2, Q_3\right) \end{aligned}\end{split}\]