TeixeiraWaterIqt

Description

It models the intermediate scattering function for the inelastic spectra of water molecules, based on Teixeira’s model [1].

Fs(Q,t)=AR(Q,t)T(Q,t)T(Q,t)=eΓtR(Q,t)=j02(Qa)+3j12(Qa)et/3τ1+5j22(Qa)et/τ1

where:

  • jn(x) are the spherical bessel functions of order n.

  • A is the amplitude.

  • Γ is the spectrum linewidth.

  • τ1 is the relaxation time associated with rotation diffusion.

  • Q is the elastic momentum transfer, 0.41 by default, but should be set to a correct value prior to fitting.

  • a is the molecular radius of rotation, set by default to 0.98.

Units of a are inverse units of Q.

Units of Γ inverse units of t. After fitting, if scaled by correct , units are meV if units of τ1 are ps. Alternatively, units of Γ are μeV if units of τ1 are ns.

Attributes (non-fitting parameters)

Name

Type

Default

Description

Q

a

Properties (fitting parameters)

Name

Default

Description

Amp

1.0

Amplitude

Tau1

0.05

Relaxation time

Gamma

1.2

Line Width

References

Categories: FitFunctions | QuasiElastic

Source

Python: TeixeiraWaterIqt.py