Skip to content

Latest commit

 

History

History
42 lines (27 loc) · 1.24 KB

InelasticDiffSphere.rst

File metadata and controls

42 lines (27 loc) · 1.24 KB

InelasticDiffSphere

.. index:: InelasticDiffSphere

Description

This fitting function models the inelastic part of the dynamics structure factor of a particle undergoing continuous diffusion but confined to a spherical volume, :ref:`DiffSphere <func-DiffSphere>`.

S(Q,E\equiv \hbar \omega) = \frac{1}{\pi} \sum_{l=1}^{N-1} (2l+1) A_{n,l} (Q\cdot R) \frac{x_{n,l}^2 D/R^2}{[x_{n,l}^2 D/R^2]^21+\omega^2}
A_{n,l} = \frac{6x_{n,l}^2}{x_{n,l}^2-l(l+1)} [\frac{QRj_{l+1}(QR) - lj_l(QR)}{(QR)^2 - x_{n,l}^2}]^2

Because of the spherical symmetry of the problem, the structure factor is expressed in terms of the j_l(z) spherical Bessel functions.

The value of the momentum transfer can be obtained either through attribute Q, or can be calculated from the input workspace using attribute WorkspaceIndex. The value calculated using the workspace is used whenever attribute Q is set empty.

.. attributes::

Q (double, default=1.0) Momentum transfer - WorkspaceIndex (integer, default=0)

.. properties::

.. categories::

.. sourcelink::