Preferred Label : rotational correlation time;
Detailed label : rotational correlation time, τc or θ;
IUPAC definition : Parameter describing the time dependence of the tumbling of a molecular entity in
a medium of viscosity η. The rotational correlation time can be obtained from the
decay of the fluorescence or phosphorescence anisotropy and is related to the u average
/u molecular rotational diffusion coefficient, Dr, in turn related to the hydrodynamic
molecular volume of the fluorophore, V, and to η (see Note 3).;
Scope note : often, the stokes–einstein relationship is used for the calculation of dr, i.e.,
dr r t 6 v ¿ withrthe
gas constant, t the absolute temperature andv the hydrodynamic molecular volume.
however, the use of this relationship at a molecular level is questionable, anddr
should be independently determined by time-resolved fluorescence polarization methods.compare
with rotational relaxation time.; in the case of a spherical emitting species reorienting itself in a homogeneous fluid,
tc 1 6 dr .; mathematical definition: rt r0 t tc
withrt the emission anisotropy at timet and r0the fundamental emission anisotropy.;
Origin ID : RT07474;
See also
Parameter describing the time dependence of the tumbling of a molecular entity in
a medium of viscosity η. The rotational correlation time can be obtained from the
decay of the fluorescence or phosphorescence anisotropy and is related to the u average
/u molecular rotational diffusion coefficient, Dr, in turn related to the hydrodynamic
molecular volume of the fluorophore, V, and to η (see Note 3).
