Hall-Ross¶

Description¶

Models the Q dependence of the QENS line width (Gamma (hwhm)), diffusion coefficients (D), residence times (tau) and jump lengths (l) to extract the associated long range diffusive motions of molecules.

The Hall-Ross Jump diffusion model [1] has the form:

$Gamma(Q) = \frac{\hbar}{\tau} \cdot (1-exp(-l*Q^2))$

Units of $l$ are inverse units of $Q$ .

Units of $Gamma$ are $meV$ if units of $\tau$ are ps. Alternatively, units of $Gamma$ are $\mu eV$ if units of $\tau$ are ns.

Properties (fitting parameters)¶

Name	Default	Description
Tau	1.0	Residence time
L	0.2	Jump length

References¶

[1]	P L Hall & D K Ross Mol Phys 36 1549 (1978)

Categories: FitFunctions | QuasiElastic

Source¶

Python: HallRoss.py (last modified: 2019-11-13)