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# 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:

\[ \begin{align}\begin{aligned}HWHM(Q) = \frac{\hbar}{\tau} \cdot \frac{(QL)^2}{6 + (QL)^2}\\D = \frac{L^2}{6 \tau}\end{aligned}\end{align} \]

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¶

**Categories**: FitFunctions | QuasiElastic

## Source¶

Python: TeixeiraWater.py