TeixeiraWater

Description

Teixeira’s model for water [1].

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

This model (1961) has the form:

HWHM(Q) = \frac{\hbar}{\tau} \cdot \frac{(QL)^2}{6 + (QL)^2}

D = \frac{L^2}{6 \tau}

Units of L are inverse units of Q.

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

Properties (fitting parameters)

Name Default Description
Tau 1.0 Residence time
L 1.5 Jump length

References

[1]
  1. Teixeira, M.-C. Bellissent-Funel, S. H. Chen, and A. J. Dianoux. Phys. Rev. A, 31:1913–1917

Categories: FitFunctions | QuasiElastic

Source

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